Thermoelectric power generating element, thermoelectric power generating battery, and power generation stabilizing method

Abstract

The purpose of the present invention is to provide a thermoelectric power generating battery having excellent battery characteristics.　The problem can be addressed using the thermoelectric power generating element not requiring a temperature gradient of the present invention. In this thermoelectric power generating element, a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion that includes an electrolyte through which a charge transport ion pair can move, and a third portion including a material that serves as an electrode are in contact in this order. The valence band potential of the semiconductor of the first portion is more positive than the oxidation-reduction potential of the charge transport ion pair, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion. This thermoelectric power generating element also satisfies formula (I): L / IDT = 1 to 20 (I) (in the formula, L is "the shortest distance between the first portion and the second portion," and IDT is "ion diffusion thickness").

Description

Thermoelectric power generation element, thermoelectric battery, and method for stabilizing power generation

[0001] The present invention relates to a thermoelectric power generating element and a method for stabilizing power generation.

[0002] Conventionally, thermoelectric power generation utilizing the Seebeck effect has been known as a thermoelectric power generation method that utilizes geothermal energy or factory waste heat, etc. (Patent Documents 1 and 2, and Non-Patent Document 1), and practical application is expected for efficient use of thermal energy. Thermoelectric power generation using the Seebeck effect is a power generation principle that utilizes the generation of voltage when a temperature gradient is applied to a metal or semiconductor. Specifically, it is a thermoelectric power generation system that converts thermal energy into electrical energy by applying a temperature gradient to a thermoelectric conversion element that combines a p-type semiconductor and an n-type semiconductor.

[0003] However, conventional thermoelectric conversion elements that utilize a temperature gradient have problems such as the high cost of the semiconductors that make up the thermoelectric conversion element, a high operating temperature range, and low conversion efficiency. Furthermore, the physical durability of the joints is poor, making it impossible to install them in places where they are subject to vibration. Furthermore, since a temperature gradient is required for power generation, installation locations are limited, and in some cases, a cooling device for the temperature gradient is required. In particular, because one dimension of the thermoelectric conversion module is used for the temperature gradient, the heat source is utilized in two dimensions, and all surrounding heat cannot be utilized in three dimensions, resulting in low heat utilization efficiency.

[0004] Japanese Patent Application Laid-Open No. 2010-147236 Japanese Patent Application Laid-Open No. 2003-219669 International Publication No. 2017 / 038988 International Publication No. 2020 / 031992

[0005] "Renewable and Sustainable Energy Reviews" (Netherlands), 2014, Vol. 33, p. 371

[0006] The present inventors have developed a thermoelectric power generation element that can convert thermal energy into electrical energy by combining a semiconductor that generates thermally excited electrons and holes with a specific electrolyte (Patent Document 3). However, they felt that further improvements in battery characteristics, such as increased short-circuit current, improved discharge capacity, increased number of discharges or extended discharge time, and lower power generation temperature, were necessary. Therefore, an object of the present invention is to provide a thermoelectric power generation battery with excellent battery characteristics.

[0007] As a result of extensive research into thermoelectric batteries with excellent battery characteristics, the inventors have surprisingly found that battery characteristics can be improved by optimizing the thickness of the electrolyte between the semiconductor and the electrode depending on the electrolyte. The present invention is based on this finding.Therefore, the present invention provides: [1] a thermoelectric power generation element that does not require a temperature gradient, in which a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte in which charge-transporting ion pairs can move, and a third portion including a substance that serves as an electrode are in contact with each other in this order, the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge-transporting ion pairs, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion, and the thermoelectric power generation element that does not require a temperature gradient satisfies the following formula (I): L / IDT=1 to 20(I) (wherein L is the "shortest distance between the first portion and the third portion" and IDT is the "ion diffusion thickness"); [2] the thermoelectric power generation element according to [1], in which the first portion, the second portion, and the third portion are layered; [3] The thermoelectric power generation element according to [1], wherein the first portion, the second portion, and the third portion are concentrically arranged; [4] A thermoelectric power generation device including the thermoelectric power generation element according to any one of [1] to [3]; [5] A thermoelectric battery including the thermoelectric power generation element according to any one of [1] to [3]; [6] A thermoelectric power generation module including the thermoelectric power generation element according to any one of [1] to [3]; [7] A method for stabilizing power generation in a thermoelectric power generation element that does not require a temperature gradient, in which a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte in which charge-transporting ion pairs can move, and a third portion including a substance that serves as an electrode are in contact with each other in this order, the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge-transporting ion pairs, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion, characterized in that the value of L / IDT (where L is the "shortest distance between the first portion and the third portion" and IDT is the "ion diffusion thickness") is set to 1 to 20.

[0008] The thermoelectric generating element of the present invention exhibits excellent discharge capacity, short-circuit current, number of discharges, discharge time, etc. Furthermore, the temperature range in which power can be generated is widened, and power can be generated in either a low temperature range or a high temperature range.

[0009] 1 is a diagram schematically illustrating a thermoelectric power generation element of the present invention; FIG. 2 is a diagram schematically illustrating a specific embodiment of a thermoelectric power generation element of the present invention; FIG. 3 is a graph plotting measured values ​​of AC impedance for a thermoelectric power generation element of the present invention; FIG. 4 is a graph showing an outline of a sheet-type battery of Example 1 (A), an open-circuit voltage at 80°C (B), and a change in acquired voltage (C); FIG. 5 is a graph showing an outline of a comb-shaped electrode of Example 2 (A), power generation characteristics (B, C), and a change in ion diffusion thickness with temperature (D); FIG. 6 is a graph showing the relationship between short-circuit current and L / IDT for the batteries of Examples 1 and 2; FIG. 7 is a graph showing the relationship between discharge capacity and L / IDT for the batteries of Examples 3 and 4; FIG. 8 is a graph showing the relationship between discharge time (A), open-circuit voltage (B), and L / IDT and discharge time for the battery of Example 5; FIG. 9 is a graph showing the relationship between short-circuit current at 80°C and L / IDT for the battery of Example 6; FIG. 10 is a graph showing the relationship between short-circuit current at 90°C and L / IDT for the battery of Example 7; and FIG. 11 is a graph showing the relationship between electrical capacity at 80°C and L / IDT for the battery of Example 8. 10 is a graph showing the battery characteristics of the battery of Example 9 at 30° C. and 80° C.

[0010] [1] Thermoelectric power generation element and thermoelectric battery The thermoelectric power generation element of the present invention is a thermoelectric power generation element that does not require a temperature gradient, and that includes a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte through which charge-transporting ion pairs can move, and a third portion including a substance that serves as an electrode, which are in contact with each other in this order, wherein the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge-transporting ion pairs, an oxidation reaction of the more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the more easily reduced of the two ions occurs at the interface between the third portion and the second portion, and that satisfies the following formula (I): L / IDT=1 to 20 (I) (wherein L is the "shortest distance between the first portion and the third portion," and IDT is the "ion diffusion thickness").

[0011] <<First Part>> The first part is not particularly limited as long as it includes a semiconductor (hereinafter, sometimes referred to as the "first semiconductor") that generates thermally excited electrons and holes. The semiconductor that generates thermally excited electrons and holes is a thermoelectric conversion material. The valence charge potential of the semiconductor is more positive than the redox potential of the charge transport ion pair. Therefore, at the interface between the first part and the second part of the present invention, the more easily oxidized ion of the charge transport ion pair is oxidized and becomes the other ion. The potential difference between the redox potential of the charge transport ion pair in the second part and the valence charge potential of the semiconductor is not limited as long as the effects of the present invention are obtained, but is preferably 0 to 1.0 V, more preferably 0.05 to 0.5 V, and even more preferably 0.05 to 0.3 V. For example, β-FeSi ２ CuZr relative to the valence electron charge potential ２ (P.O. ４ ) ３ The difference in redox potential between Cusicon (a copper ion conductor) and CuSiC (a copper ion conductor) is approximately 0.05 V. For materials for which the redox potential of the charge-transporting ion pair and the valence potential of the semiconductor have been measured, a person skilled in the art can select an appropriate ion for the semiconductor and an electrolyte in which the ion can migrate based on the values ​​of the redox potential and valence potential. Furthermore, for materials for which the valence potential of the semiconductor and the redox potential of the charge-transporting ion pair are unknown, it is possible to measure the valence potential of the semiconductor and the redox potential of the ion. Therefore, a person skilled in the art can select an appropriate charge-transporting ion pair electrolyte depending on the selected semiconductor.

[0012] (First Semiconductor) The first semiconductor is not particularly limited as long as it can generate thermally excited electrons and holes by applying an appropriate temperature, and examples thereof include metal semiconductors, tellurium compound semiconductors, silicon germanium (Si-Ge) compound semiconductors, silicide compound semiconductors, skutterudite compound semiconductors, clathrate compound semiconductors, Heusler compound semiconductors, half-Heusler compound semiconductors, metal oxide semiconductors, organic semiconductors, sulfide semiconductors, and other semiconductors. The semiconductor used in the present invention functions as a thermoelectric conversion material. Examples of metal semiconductors include Si semiconductors and Ge semiconductors. Examples of tellurium compound semiconductors include Bi-Te compounds (for example, Bi ２ Te ３ , Sb ２ Te ３ , CsBi ４ Te ６ , Bi ２ Se ３ , Bi ０．４ Sb １．６ Te ３ , Bi ２ (Se, Te) ３ , (Bi, Sb) ２ (Te, Se) ３ , (Bi, Sb) ２ Te ３ , or Bi ２ Te ２．９５ Se ０．０５ ), Pb—Te compounds (e.g., PbTe or Pb １－ｘ Sn ｘ Te), SnTe, Ge-Te, AgSbTe ２ , Ag—Sb—Ge—Te compounds (e.g., GeTe—AgSbTe ２ (TAGS)), Ga ２ Te ３ , (Ga １－ｘ In ｘ ) ２ Te ３ , Tl ２ Te-Ag ２ Te, Tl ２ Te-Cu ２ Te, Tl ２ Te-Sb ２ Te ３, Tl ２ Te-Bi ２ Te ３ , Ti ２ Te-GeTe, Ag ８ Tl ２ Te ５ , Ag ９ TlTe ５ , Tl ９ BiTe ６ , Tl ９ SbTe ６ , Tl ９ CuTe ５ , Tl ４ SnTe ３ , Tl ４ PbTe ３ , or Tl ０．０２ Pb ０．９８ Examples of silicon germanium (Si-Ge) compound semiconductors include Si ｘ Ge １－ｘ , or SiGe-GaP. Silicide compound semiconductors include β-FeSi ２ Compounds (e.g., β-FeSi ２ , Fe １－ｘ Mn ｘ Si ２ , Fe ０．９５ Mn ０．０５ Si （２－ｙ） Al ｙ , FeSi （２－ｙ） Al ｙ , Fe １－ｙ Co ｙ Si ２ ), Mg ２ Si, MnSi １．７５－ｘ , Ba ８ Si ４６ , Ba ８ Ga １６ Si ３０ , or CrSi ２ Examples of the skutterudite compound semiconductor include those represented by the formula TX ３ wherein T is a transition metal selected from the group consisting of Co, Fe, Ru, Os, Rh, and Ir, and X is a pnictogen selected from the group consisting of P, As, and Sb; ４ X１２ (wherein R is a rare earth selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M is selected from the group consisting of Fe, Ru, Os, and Co; and X is selected from the group consisting of P, As, and Sb), a compound represented by the formula: Yb ｙ Fe ４－ｘ Co ｘ Sb １２ , (CeFe ３ CoSb １２ ) １－ｘ (MoO ２ ) ｘ or (CeFe ３ CoSb １２ ) １－ｘ (W.O. ２ ) ｘ Examples of clathrate compound semiconductors include those of the formula M ８ X ４６ (M is selected from the group consisting of Ca, Sr, Ba, and Eu, and X is selected from the group consisting of Si, Ge, and Sn), a compound represented by formula (II) ８ (III) １６ (IV) ３０ (wherein II is a Group II element, III is a Group III element, and IV is a Group IV element) ８ (III) １６ (IV) ３０ Examples of the compound include Ba ８ Ga ｘ Ge ４６－ｘ , Ba ８－ｘ (Sr, Eu) ｘ Au ６ Ge ４０ , or Ba ８－ｘ EU ｘ Cu ６ Si ４０ Examples of Heusler compound semiconductors include Fe ２ Val, (Fe １－ｘ Re ｘ ) ２ Val or Fe ２ (V １－ｘ－ｙ Tiｘ Ta ｙ )Al can be mentioned. Examples of half-Heusler compound semiconductors include a compound represented by the formula MSiSn (wherein M is selected from the group consisting of Ti, Zr, and Hf), a compound represented by the formula MNiSn (wherein M is Ti or Zr), a compound represented by the formula MCoSb (wherein M is selected from the group consisting of Ti, Zr, and Hf), or a compound represented by the formula LnPdX (wherein Ln is selected from the group consisting of La, Gd, and Er, and X is Bi or Sb). Examples of metal oxide semiconductors include In ２ O ３ -SnO ２ , (CaBi)MnO ３ , Ca(Mn,In)O ３ , Na ｘ V ２ O ５ , V ２ O ５ , ZnMnGaO ４ and its derivatives, LaRhO ３ , LaNiO ３ , SrTiO ３ , SrTiO ３ : Nb, Bi ２ Sr ２ Co ２ O ｙ , Na ｘ CoO ２ , NaCo ２ O ４ , CaPd ３ O ４ , formula Ca ａ M １ ｂ Co ｃ M ２ ｄ Ag ｅ O ｆ (In the formula, M １ is one or more elements selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y and rare earth elements, and M ２is one or two elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Mo, W, Nb, Ta, and Bi, and the following relationships are satisfied: 2.2≦a≦3.6, 0≦b≦0.8, 2≦c≦4.5, 0≦d≦2, 0≦e≦0.8, 8≦f≦10; ZnO, Na(Co,Cu) ２ O ４ , ZnAlO, Zn １－ｘ Al ｘ O or La １．９８ Sr ０．０２ CuO ４ Examples of organic semiconductors include organic perovskite, polyaniline, polyacetylene, polythiophene, polyalkylthiophene, and polypyrrole. Examples of sulfide semiconductors include Ag ２ Other thermoelectric conversion compounds include alloys containing Co and Sb (e.g., CoSb ３ , CeFe ３ CoSb １２ , CeFe ４ CoSb １２ , or YbCo ４ Sb １２ ), alloys containing Zn and Sb (e.g., ZnSb, Zn ３ Sb ２ , or Zn ４ Sb ３ ), alloys containing Bi and Sb (e.g., Bi ８８ Sb １２ ), CeInCu ２ , (Cu, Ag) ２ Se, Gd ２ Se ３ , CeRhAs, or CeFe ４ Sb １２ , Li ７．９ B １０５ , BaB ６ , SrB ６ , CaB ６ , AlPdRe compounds (e.g., Al ７１ Pd ２０ (Re １－ｘ Fe ｘ ) ９ ), AlCuFe quasicrystal, Al ８２．６－ｘ Re１７．４ Si ｘ 1 / 1-cubic approximation crystal, YbAl ３ , YbMn ｘ Al ３ , β-CuAgSe, B ４ C / Ba ３ C, (Ce １－ｘ La ｘ ) Ni ２ , or (Ce １－ｘ La ｘ ) In ３ Examples include:

[0013] The first portion may further include an electron transport material in addition to the first semiconductor. The electron transport material is located on the opposite side of the semiconductor contact surface to the second portion. Examples of the electron transport material include semiconductors and metals. The electron conduction potential of the electron transport material is the same as or positive to the conduction potential of the semiconductor (first semiconductor) that generates thermally excited electrons and holes.

[0014] The electron conduction potential of the electron transport material is not particularly limited as long as it is the same as or positive to the conduction potential of the first semiconductor. Examples of the electron transport material include semiconductors and metals. Specific examples of the electron transport material include N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, or electron-transporting organic compounds containing at least one selected from the group consisting of niobium, titanium, zinc, tin, vanadium, indium, tungsten, tantalum, zirconium, molybdenum, and manganese. More specific examples include titanium oxide, tungsten oxide, zinc oxide, niobium oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, or SrTiO. ３Examples of the electron-transporting organic material include N-type conductive polymers, N-type small-molecular organic semiconductors, π-electron conjugated compounds, surfactants, and specific examples thereof include oxadiazole derivatives, triazole derivatives, perylene derivatives, quinolinol metal complexes, cyano group-containing polyphenylene vinylenes, boron-containing polymers, bathocuproine, bathophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalene tetracarboxylic acid compounds, perylene derivatives, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, fullerenes and derivatives thereof, phenylene vinylene polymers, and perylene tetracarboxylic acid imide derivatives.

[0015] The potential difference between the electron conduction potential of the electron transport material and the conduction potential of the first semiconductor is not limited as long as the effects of the present invention can be obtained, but is preferably 0.01 to 1 V, more preferably 0.01 to 0.5 V, even more preferably 0.01 to 0.3 V, and most preferably 0.05 to 0.2 V. For example, β-FeSi ２ The potential difference between the conduction potential of n-type silicon and the conduction potential of n-type silicon, i.e., the electronic conduction potential, is approximately 0.01 V. For materials for which the conduction potential of the first semiconductor and the electronic conduction potential of the electron transport material have been measured, a person skilled in the art can appropriately select an appropriate electron transport material for the first semiconductor in the first portion according to the values ​​of these potentials. Furthermore, for materials for which the conduction potential of the semiconductor and the electronic conduction potential of the electron transport material are unknown, these potentials can be measured, for example, by electrochemical measurement or inverse photoemission spectroscopy (XPS). Therefore, a person skilled in the art can appropriately select an appropriate electron transport material depending on the first semiconductor in the first portion used in the thermoelectric power generation element.

[0016] The first semiconductor in the first portion can be fabricated by, for example, a squeegee method, a screen printing method, a spark plasma sintering method, a compression molding method, a sputtering method, a vacuum deposition method, or a spin coating method. ２The first semiconductor can be fabricated by dispersing the above in a polar solvent such as acetone and spin-coating the solution onto the electron transport material or the second portion. ２ was produced by spark plasma sintering, and the resulting β-FeSi ２ The powder and a conductive binder (e.g., a high-temperature conductive coating) may be squeegeeed onto the electron transport material or the second portion. The electron transport material can also be prepared by, for example, a squeegee method, a screen printing method, a sputtering method, a vacuum deposition method, a single crystal growth method, or a spin coating method. When using a spin coating method, the electron transport material can be prepared by dissolving the oxadiazole derivative in a polar solvent such as acetone and spin-coating the solution onto a substrate or the first semiconductor. For example, n-type silicon, which will be described later, can be obtained by a single crystal growth method, and the first semiconductor can be laminated on this n-type silicon as a substrate.

[0017] The first portion constituting the thermoelectric power generation element of the present invention may contain other components as long as the first semiconductor can generate a sufficient number of thermally excited electrons and holes for power generation when heated to an appropriate temperature. Examples of such components include, but are not limited to, binders (polyvinyl alcohol, methyl cellulose, acrylic resin, agar, etc.) and sintering aids (magnesium oxide, yttrium oxide, calcium oxide, etc.) that help form the first semiconductor. Solvents used in the manufacturing process may also remain. The first portion used in the present invention essentially functions as a thermoelectric conversion layer.

[0018] <<Second Portion>> The second portion is not particularly limited as long as it contains an electrolyte through which the charge-transporting ion pair can move. Examples of the electrolyte include solid electrolytes and electrolyte solutions. The electrolyte is not particularly limited as long as it can transport two ions of the charge-transporting ion pair. That is, the electrolyte contained in the second portion is not particularly limited as long as its redox potential is appropriately positioned with respect to the valence potential of the first semiconductor used in the thermoelectric power generation element and the charge-transporting ion pair can move back and forth within the electrolyte. Note that the electrolyte is preferably physically and chemically stable at a temperature at which the first semiconductor generates a sufficient number of thermally excited electrons and holes for power generation.

[0019] The electrolyte may be a solid electrolyte or an electrolyte solution (liquid electrolyte) depending on its form. Here, the electrolyte may be in the form of an electrolyte solution (liquid electrolyte) or a solid electrolyte depending on the temperature. That is, the compounds contained in the electrolyte solution (liquid electrolyte) and the compounds contained in the solid electrolyte overlap. Furthermore, the electrolyte includes molten salts, ionic liquids, deep eutectic solvents, etc. Molten salts refer to salts composed of cations and anions in a molten state. Molten salts with relatively low melting points (e.g., 100°C or less, or 150°C or less) are referred to as ionic liquids. However, in this specification, molten salts in a solid state are referred to as solid electrolytes, and those in a solution state are referred to as electrolyte solutions (liquid electrolytes). Specific examples of electrolyte solutions (liquid electrolytes), solid electrolytes, and molten salts are provided below, but these terms may overlap. The electrolyte solution used is in a solution (liquid) state at a temperature at which the semiconductor in the first portion generates a sufficient number of thermally excited electrons and holes for power generation. Specific examples of the electrolyte solution include, but are not limited to, methoxide ions, hydrogen ions, ammonium ions, pyridinium ions, lithium ions, sodium ions, potassium ions, calcium ions, magnesium ions, aluminum ions, iron ions, copper ions, zinc ions, cobalt ions, fluoride ions, cyanide ions, thiocyanate ions, chloride ions, acetate ions, sulfate ions, carbonate ions, phosphate ions, bicarbonate ions, and bromine ions.

[0020] The solid electrolyte is in a solid state in which charge-transporting ion pairs can move inside at a temperature at which the semiconductor of the first portion generates a sufficient number of thermally excited electrons and holes for power generation. The use of a high-temperature solid electrolyte allows it to be used in a thermoelectric power generation element that uses a thermoelectric power generation element that generates thermally excited electrons and holes at high temperatures. Specific examples of the solid electrolyte include, but are not limited to, sodium ion conductors, copper ion conductors, lithium ion conductors, silver ion conductors, hydrogen ion conductors, strontium ion conductors, aluminum ion conductors, fluorine ion conductors, chloride ion conductors, and oxide ion conductors. Specific examples of the solid electrolyte include RbAg ４ I ５ , Li ３ N, Na ２ O.11Al ２ O ３ , Sr-β alumina, Al(WO ４ ) ３ , PbF ２ , PbCl ２ , (ZrO ２ ) ０．９ (Y ２ O ３ ) ０．１ , (Bi ２ O ３ ) ０．７５ (Y ２ O ３ ) ０．２５ , CuZr ２ (P.O. ４ ) ３ , CuTi ２ (P.O. ４ ) ３ , Cu ｘ Nb １－ｘ Ti １＋ｘ (P.O. ４ ) ３ , H ０．５ Cu ０．５ Zr ２ (P.O. ４ ) ３ , Cu １＋ｘ Cr ｘ Ti ２－ｘ (P.O. ４ ) ３ , Cu ０．５ TiZr(PO ４ )３ ,CuuCr ２ Zhr(PO ４ ) ３ 、Cu ２ ScCr(PO ４ ) ３ 、CuSumn ２ (PO ４ ) ３ 、C･uｨf ２ (PO ４ ) ３ 、Li ７ La ３ Zr ２ O １２ 、Li ７ La ３ Zr ２－ｘ N｡ ｘ O １２ 、Li ７ La ３ Zr ２－ｘ TakO １２ , Li ５ La ３ That ２ O １２ , Li ０．３３ La ０．５５ TiO ３ , Li １．５ Al ０．５ Yes １．５ P ３ O １２ , Li １．３ Al ０．３ Ti １．７ P ３ O １２ , Li ３ PO ４ (LiPON),Li ４ SiO ４ -Li ３ PO ４ , Li ４ SiO ４ 、 or ３ BO ３Examples include: molten salts. Furthermore, a molten salt can be used as the solid electrolyte or electrolyte solution. For thermoelectric power generation elements used at relatively low temperatures, an ionic liquid can also be used. Deep eutectic solvents (DES) can be used as the ionic liquid. Examples of molten salts include those containing at least one cation selected from the group consisting of imidazolium cations, pyridinium cations, piperidinium cations, pyrrolidinium cations, phosphonium cations, morpholinium cations, sulfonium cations, and ammonium cations, and at least one anion selected from the group consisting of carboxylate anions, sulfonate anions, halogen anions, tetrafluoroborate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, and bis(fluorosulfonyl)imide. The electrolyte in the present invention functions as a hole-transporting material.

[0021] In addition, in this specification, the term "charge transport ion pair" refers to two stable ions with different valences, in which one ion is oxidized or reduced to become the other ion, and can transport electrons and holes. Ions of the same element with different valences may also be used. For example, in the case of copper ions, monovalent copper ions and divalent copper ions are preferred, and in the case of iron ions, divalent iron ions and trivalent iron ions are preferred. As monovalent copper ions, for example, CuCl, CuBr, copper(I) acetate, copper(I) iodide, or copper(I) sulfate can be used. As divalent copper ions, CuCl ２ , CuTSFI ２ , copper(II) acetate, copper(II) sulfate, or copper(II) acetylacetonate can be used. As the divalent iron ion, Fe(C ５ H ５ ) ２ (Ferrocene), K ４ [Fe(CN) ６ ], iron(II) acetylacetonate, iron(II) chloride, iron(II) sulfate, or iron(II) acetate can be used. ３ , K. ３ [Fe(CN) ６], iron(III) acetylacetonate or iron(III) sulfate can be used.

[0022] An oxidation reaction of the more easily oxidized ion of the two ions occurs at the interface between the first and second portions, and a reduction reaction of the more easily reduced ion of the two ions occurs at the interface between the third and second portions. In the present invention, the valence charge potential of the first semiconductor in the first portion is more positive than the redox potential of the charge-transporting ion pair in the second portion. Therefore, at the interface between the first and second portions (electrolyte) of the present invention, the more easily oxidized ion of the charge-transporting ion pair is oxidized and becomes the other ion. The potential difference between the redox potential of the charge-transporting ion pair in the electrolyte and the valence charge potential of the thermoelectric conversion material is not limited as long as the effects of the present invention are obtained, but is preferably 0 to 1.0 V, more preferably 0.05 to 0.5 V, and even more preferably 0.05 to 0.3 V. For example, in β-FeSi ２ CuZr relative to the valence electron charge potential ２ (P.O. ４ ) ３ The difference in redox potential between Cusicon (a copper ion conductor) and Cusicon is approximately 0.05 V. For materials for which the redox potential of the charge-transporting ion pair and the valence potential of the thermoelectric conversion material have been measured, a person skilled in the art can appropriately select an appropriate ion for the thermoelectric conversion material and select an electrolyte in which the ion can migrate based on the values ​​of the redox potential and valence potential. Furthermore, for materials for which the valence potential of the first semiconductor and the redox potential of the charge-transporting ion pair are unknown, it is possible to measure the valence potential of the first semiconductor and the redox potential of the ion. Therefore, a person skilled in the art can appropriately select an appropriate charge-transporting ion pair electrolyte depending on the selected first semiconductor.

[0023] The thermal power generating battery of the present invention preferably contains alkali metal ions as additives in the second part (Patent Document 4). Examples of alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, and francium ions, with lithium ions, sodium ions, and potassium ions being preferred. By including alkali metal ions, the battery life can be extended and discharge characteristics can be restored by leaving the battery in a heat source. The alkali metal ions are not limited to, but include, for example, halides, perchlorates (e.g., LiClO ４ The alkali metal ions may be added to the electrolyte in the form of a salt thereof, a sulfate, or a strong acid salt. For example, alkali metal compounds can be used in various forms as long as they do not degrade the solvent. Examples of halogens that form halides with alkali metal ions include fluorine, chlorine, bromine, iodine, and astatine. For example, examples of compounds of alkali metal ions with chlorine include LiCl, NaCl, KCl, RbCl, CsCl, and FrCl.

[0024] The amount of the alkali metal compound added is not particularly limited as long as it can extend the battery life, but is, for example, 0.001 to 100 parts by weight, preferably 0.01 to 10 parts by weight, and more preferably 0.03 to 0.1 parts by weight, relative to 100 parts by weight of the electrolyte. By using the alkali metal compound in this range, an especially excellent effect of extending the battery life can be obtained.

[0025] The second part may contain components other than the solid electrolyte or the electrolyte solution, such as, but not limited to, a polar solvent (water, methanol, toluene, tetrahydrofuran, etc.) that dissolves or disperses the electrolyte when preparing the second part, a binder (polyvinyl alcohol, methyl cellulose, acrylic resin, agar, etc.) that binds the electrolyte, and a sintering aid (magnesium oxide, yttrium oxide, calcium oxide, etc.) that helps form the hole transporting material.

[0026] The second portion can be fabricated by, for example, a squeegee method, a screen printing method, a sputtering method, a vacuum deposition method, a sol-gel method, or a spin coating method. ２ (P.O. ４ ) ３ is prepared by a sol-gel method. The obtained sol can be prepared as the second portion by a squeegee method. Furthermore, when the electrolyte is an electrolyte solution (liquid electrolyte), the second portion is in a liquid phase. When the second portion is in a liquid phase, the second portion in the thermoelectric power generation element is preferably prepared during the preparation of the thermoelectric power generation device, thermobattery, or thermoelectric power generation module. That is, the second portion can be prepared by providing a tank for holding the electrolyte solution (liquid electrolyte).

[0027] The third portion is not particularly limited as long as it contains a material that can be used as an electrode. The material that can be used as an electrode is not particularly limited as long as it can transport electrons, and examples thereof include fluorine-doped tin oxide (FTO), tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), zinc oxide (ZnO), and indium oxide (In ２ O ３ ), tin oxide (SnO ２ ), IZO (In—Zn—O), or IGZO (In—Ga—Zn—O). Also included are metals that do not react with charge-transporting ion pairs, such as titanium, gold, platinum, silver, copper, tin, tungsten, niobium, tantalum, stainless steel, aluminum, graphene, molybdenum, indium, vanadium, rhodium, niobium, chromium, nickel, carbon, alloys thereof, or combinations thereof. The third portion may be provided as a layer or in the form of a conductor. In the case of a layer, it can be manufactured by vacuum deposition, spin coating, or the like.

[0028] When an appropriate temperature is applied to the first semiconductor, a sufficient number of thermally excited electrons and holes are generated to generate electricity. Because the redox potential of the electrolyte contained in the second portion is negative relative to the valence electron charge potential of the first semiconductor in the first portion, holes are transported from the first portion to the third portion (sometimes referred to as the positive electrode). That is, oxidation and reduction of ions occur in the electrolyte, and electrons are transported from the third portion (positive electrode) to the first portion, and holes are transported from the first portion to the third portion (positive electrode). Through this mechanism, electrons move, generating electricity.

[0029] The thermoelectric power generation element of the present invention satisfies the following formula (I): L / IDT=1 to 20 (I) (wherein L is the "shortest distance between the first portion and the third portion," and IDT is the "ion diffusion thickness." The lower limit of L / IDT is 1 or more, preferably 1.5 or more, and more preferably 2 or more. The upper limit of L / IDT is 20 or less, preferably 15 or less, more preferably 10 or less, even more preferably 8 or less, and most preferably 5 or less. The lower limit and upper limit can be combined as appropriate.

[0030] The "shortest distance between the first and third portions" will be explained using FIG. 2. FIG. 2 schematically shows several specific embodiments of the thermoelectric power generation element of the present invention. For example, in the thermoelectric power generation element of the present invention, the first portion, second portion, and third portion can be stacked in layers ( FIG. 2A ). In this case, the thickness L of the second portion is the "shortest distance between the first and third portions." As shown in FIG. 2B , the first portion, second portion, and third portion can also be arranged on a single plane. This arrangement is also included in the case where the first portion, second portion, and third portion are stacked in layers. In this case, the thickness L (width) of the second portion sandwiched between the first and third portions is the "shortest distance between the first and third portions." In the thermoelectric power generation element of the present invention, the first portion, second portion, and third portion can be arranged concentrically ( FIGS. 2C and 2D ). For example, as shown in FIG. 2C , the first portion can be arranged at the center, the second portion can be arranged around it, and the third portion can be arranged around that. Alternatively, as shown in FIG. 2D , the third portion can be disposed at the center, the second portion can be disposed around it, and the first portion can be disposed around that. In either case, the thickness L (thickness of the thinnest part) of the second portion between the first and third portions is the "shortest distance between the first and third portions." In the thermoelectric power generation element of the present invention, the second portion can be disposed in a T-shape, as shown in FIG. 2E . That is, the second portion can be disposed so that the lower part of the T of the second portion is sandwiched between the first and third portions. In this case, the thickness L of the lower second portion sandwiched between the first and third portions is the "shortest distance between the first and third portions." These thicknesses L can be measured using a vernier caliper, a contact stylus, an optical microscope, or the like.

[0031] The "ion diffusion thickness" is a specific value that can be calculated from the redox ions, electrolyte, and temperature of the second portion. However, since different values ​​may be calculated depending on the model, it is preferable to determine it by measurement. The "ion diffusion thickness" can be measured as follows. AC impedance measurement is performed on a thermoelectric power generation element (battery) having a first portion, a second portion, and a third portion. When the measured AC impedance values ​​are plotted, the resulting graph may have a shape, for example, a combination of semicircles and curves, or a combination of curves, as shown in FIG. 3. From this plotted graph, a fitting equation for the equivalent circuit is created. The ion diffusion thickness IDT (corresponding to "δ" in the equation below) is calculated using the obtained fitting equation and the following equation (II): R: gas constant, T: temperature, n: number of reaction electrons, F: Faraday constant, c ｂｕｌｋ : bulk concentration of electrolyte ions, j: imaginary number, ω: frequency, D: diffusion coefficient, δ: ion diffusion thickness

[0032] Using the ion diffusion thickness IDT obtained by the above calculation, the value of "L / IDT" can be calculated from the shortest distance L between the first and third portions and the ion diffusion thickness IDT.

[0033] The thermoelectric power generation device, thermoelectric battery, and thermoelectric power generation module of the present invention include the thermoelectric power generation element of the present invention and preferably include a negative electrode on the outside of the first portion. The electron transport material of the thermoelectric power generation element used in the thermoelectric power generation device, thermoelectric battery, and thermoelectric power generation module of the present invention can serve as the negative electrode, and the third portion serves as the positive electrode as described above. Note that even if the third portion is not present, the second portion can also serve as the positive electrode. As used herein, the term "thermoelectric battery" refers to a battery that includes the thermoelectric power generation element of the present invention and generates electricity by applying a temperature to the first semiconductor of the thermoelectric power generation element that is capable of generating thermally excited electrons and holes.

[0034] Thermoelectric power generation can be achieved using the thermoelectric power generation device, thermoelectric battery, and thermoelectric power generation module of the present invention. For example, power generation can be achieved by installing the thermoelectric power generation module or the like at a heat generation location and heating the thermoelectric power generation module with heat to generate electricity. In the step of installing the thermoelectric power generation module or the like, the thermoelectric power generation module of the present invention is installed at the heat generation location. The heat generation location is not particularly limited as long as it generates heat at a temperature equal to or higher than the temperature at which a sufficient number of excited electrons and holes are generated in the thermoelectric conversion material for power generation. Examples of heat generation locations include geothermal generation locations and waste heat generation locations such as factories. Geothermal energy is not limited to heat in the soil but also includes hot water or steam heated by geothermal energy. Geothermal energy also includes hot water or steam heated by geothermal energy from oceans, lakes, rivers, etc. The waste heat is not particularly limited, but examples include waste heat from steel furnaces, waste incinerators, substations, subways, automobiles, etc. In particular, the waste heat generated by steel furnaces and waste incineration plants, which generates a large amount of energy, is released without being utilized, and it is preferable to reuse this energy using the thermoelectric power generation method of the present invention. Furthermore, the thermoelectric power generation element of the present invention can generate electricity even at low temperatures (e.g., room temperature), and can be used in various devices that are used at room temperature.

[0035] In the power generation step, electric power is generated by heating the thermoelectric power generation module of the present invention, etc. Heat generated from the heat generation location heats the thermoelectric conversion material of the thermoelectric power generation module to a temperature at or above which a sufficient number of excited electrons and holes are generated for power generation, thereby enabling electric power to be generated from the thermoelectric power generation module.

[0036] The temperature for power generation is preferably set so that the thermally excited electron density is 10 １５ / m ３ It is more preferably 10 １８ / m ３ More preferably, it is a temperature at which ２０ / m ３ The temperature is preferably 10 ２２ / m ３The temperature at which the power generation temperature is equal to or higher than the first semiconductor. The power generation temperature basically varies depending on the first semiconductor, but a person skilled in the art can appropriately determine the power generation temperature based on the common technical knowledge in the field to which the present invention belongs and the description in this specification. The power generation temperature in the present invention is preferably a temperature at which charge transport ion pairs can move back and forth within the electrolyte. Specific temperatures are not limited, but are, for example, 5°C or higher, preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The upper limit of the temperature is also not particularly limited as long as it is a temperature at which charge transport ion pairs can move back and forth within the electrolyte, but is, for example, 1500°C or lower, preferably 1000°C or lower. The temperature at which the thermoelectric power generation element of the present invention actually generates power is determined not only by the temperature at which a sufficient number of thermally excited electrons and holes are generated for power generation in the first semiconductor in the first portion, but also by the ease of electron movement inherent to the material and the ease of electron movement at the interface with the first portion when combined with the second portion. These conditions are preferably in the range of L / IDT = 1 to 20.

[0037] [2] Method for stabilizing power generation In the method for stabilizing power generation of the present invention, a thermoelectric power generation element that does not require a temperature gradient, in which a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte in which charge-transporting ion pairs can move, and a third portion including a substance that serves as an electrode are in contact with each other in this order, the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge-transporting ion pairs, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion, has a value of L / IDT (where L is the "shortest distance between the first portion and the third portion" and IDT is the "ion diffusion thickness") of 1 to 20.

[0038] The shortest distance L between the first portion and the third portion and the ion diffusion thickness IDT can be measured and calculated in accordance with the description in the section "[1] Thermoelectric power generation element and thermoelectric battery." Specifically, the steps include: (1) measuring the shortest distance L between the first portion and the third portion; (2) measuring the AC impedance of the thermoelectric power generation element; (3) creating a fitting equation for an equivalent circuit from the obtained AC impedance value; (4) calculating the ion diffusion thickness IDT (corresponding to "δ" in the following equation) from the obtained fitting equation and the following equation (II); (R: gas constant, T: temperature, n: number of reaction electrons, F: Faraday constant, c ｂｕｌｋ : bulk concentration of electrolyte ions, j: imaginary number, ω: frequency, D: diffusion coefficient, δ: ion diffusion thickness). (5) Using the shortest distance L between the first and third portions and the ion diffusion thickness IDT, calculate L / IDT (where L is the "shortest distance between the first and third portions" and IDT is the "ion diffusion thickness"). The ion diffusion thickness is a value determined by calculation based on the "redox ions," "electrolyte," and "temperature" of the second portion. However, the calculated value varies depending on the model of the thermoelectric power generation element used as the basis for the calculation. Therefore, it is believed that measuring the AC impedance of an actually manufactured thermoelectric power generation element and creating a fitting equation for an equivalent circuit to determine the ion diffusion thickness IDT from the measured value reflects the actual ion diffusion thickness.

[0039] In the method for stabilizing power generation of the present invention, by adjusting the shortest distance L between the first portion and the third portion so that L / IDT is "1 to 20," improvements in battery characteristics such as an increase in short-circuit current and / or an increase in discharge capacity are achieved. The lower limit of L / IDT is 1 or more, and in one embodiment, 1.5 or more, and in one embodiment, 2 or more. The upper limit of L / IDT is 20 or less, in one embodiment, 15 or less, in one embodiment, 10 or less, in one embodiment, 8 or less, and in one embodiment, 5 or less. The lower limit and the upper limit can be combined as appropriate. The shortest distance L between the first portion and the third portion is adjusted so that L / IDT is within the above range.

[0040] <<Function>> Although the reason why the thermoelectric generating element of the present invention exhibits excellent battery characteristics has not been analyzed in detail, it can be presumed as follows. However, the present invention is not limited by this presumption. In a thermoelectric generating element, it is generally believed that the shorter the distance between the first portion containing a semiconductor and the third portion containing a material that serves as an electrode, the better the performance of the thermoelectric generating element (battery). However, in reality, there is an appropriate distance between the first portion and the second portion that improves the power generation performance of the thermoelectric generating element (battery). It is not easy to provide a logical explanation for why this appropriate distance between the first portion and the second portion is L / IDT = 1 to 20. However, in the examples described below, when measurements were actually taken under different conditions, such as "redox ions," "electrolyte," and "temperature," excellent battery performance was obtained in all cases within the range of L / IDT = 1 to 20. Therefore, it is presumed that a thermoelectric generating element exhibits excellent battery characteristics by setting L / IDT within the appropriate range.

[0041] The present invention will be specifically described below with reference to examples, but these examples are not intended to limit the scope of the present invention.

[0042] Example 1 In this example, the first portion was n-Si / Ge, the second portion was PEG, and CuCl, CuCl ２ A sheet-type battery was fabricated using a first part, a 1.5 cm x 2.5 cm n-Si / Ge substrate, and a third part, FTO. A 1.5 x 2.5 cm FTO transparent electrode was prepared as the third part. The second part, an electrolyte, was prepared using polyethylene glycol (PEG) with CuCl, CuCl, and LiCl. ２, and LiCl were mixed at 0.5 mmol / PEG (g), 0.5 mmol / PEG (g), and 0.6 mmol / PEG (g), respectively. The electrolyte from the second part was dropped onto the FTO transparent electrode from the third part, and the n-Si / Ge substrate from the first part was further laminated to produce a sheet-type battery as shown in the schematic diagram in Figure 4(A). Four sheet-type batteries were produced with distances of 85 μm, 114 μm, 228 μm, and 342 μm between the first and third parts. The battery characteristics of the four resulting batteries were measured at 80°C. The results are shown in Figure 4(B). As the distance between the electrodes increased, the open-circuit voltage decreased and re-discharge no longer occurred.

[0043] Example 2 In this example, Ge was used as the first moiety, PEG was used as the second moiety, and CuCl, CuCl ２ A comb-shaped battery was fabricated using a Ge electrode as the first part and a Pt electrode as the third part on a quartz substrate by sputtering. A CuCl, CuCl, and LiCl were then deposited on the PEG. ２ The second portion was a mixture of 0.5 mmol / PEG (g), 0.5 mmol / PEG (g), and 0.6 mmol / PEG (g) of PEG, respectively (Figure 5A). The comb-shaped electrode width was 2 μm. The battery characteristics were measured at 80°C and room temperature. No power generation occurred at 80°C, but power generation was confirmed at room temperature (Figures 5B and 5C). Figure 5D shows the temperature change in ion diffusion thickness. The ion diffusion thickness decreases as the temperature decreases. Compared to 40°C and 30°C, the thickness was slightly larger at 30°C, but this was thought to be due to the measurement limit of an ion diffusion thickness of 2 μm or less in this measurement.

[0044] <<Measurement of L / IDT>> For the four sheet-type batteries of Example 1 (80°C) and the comb-type batteries of Example 2 (30°C, 40°C, 50°C, and 60°C), L / IDT was calculated from the shortest distance L between the first and third portions and the ion diffusion thickness IDT. For each battery and temperature, AC impedance was measured at an amplitude of 10 mV and a frequency of 7 MHz-50 mHz. Using Zplot (Toyo Corporation), the measured values ​​were plotted, and a fitting equation for the equivalent circuit was created. The obtained fitting equation and the following equation (II) were used to calculate the ion diffusion thickness IDT (corresponding to "δ" in the equation below). R: gas constant, T: temperature, n: number of reaction electrons, F: Faraday constant, c ｂｕｌｋ : bulk concentration of electrolyte ions, j: imaginary number, ω: frequency, D: diffusion coefficient, δ: ion diffusion thickness. L / IDT was calculated from the obtained ion diffusion thickness IDT and the shortest distance L. The relationship between short-circuit current and L / IDT is shown in Figure 6. Power generation was not achieved unless the shortest distance between the first part and the third part was at least 0.5 times the ion diffusion thickness of the transport ion pair. Furthermore, power generation was weak even when it was 20 times or more.

[0045] Example 3 In this example, the first part was n-Si / Ge, the second part was PEG, and CuCl, CuCl ２ The operation of Example 1 was repeated to prepare four sheet type batteries.

[0046] Example 4 In this example, Ge was used as the first moiety, PEG was used as the second moiety, and CuCl, CuCl ２ Two interdigital batteries were fabricated by repeating the procedure of Example 2, except that the interelectrode distance was set to 2 μm or 5 μm.

[0047] Measurement of L / IDT and Discharge Capacity: The L / IDT was calculated for the four sheet-type batteries of Example 3 and the two interdigital batteries of Example 4 by repeating the "L / IDT measurement" procedure. Furthermore, the long-term discharge capacity was measured for the four sheet-type batteries of Example 3 and the two interdigital batteries of Example 4. Each battery was held at 80°C and discharged at 100 nA. The batteries were allowed to recover by leaving them at room temperature for two hours. Further, the batteries were held at 80°C and discharged at 100 nA repeatedly to obtain a third discharge capacity. The relationship between the third discharge capacity and L / IDT for each battery is shown in Figure 7. Excellent discharge capacity was observed when the L / IDT was between 1 and 20.

[0048] Example 5 In this example, Ge was used as the first moiety, PEG was used as the second moiety, and CuCl, CuCl ２ A comb-shaped battery was fabricated using LiCl and Pt as the third part. The procedure of Example 4 was repeated to fabricate two comb-shaped batteries with an inter-electrode distance of 2 μm or 5 μm. The open-circuit voltage value was maintained even as the number of discharges increased at room temperature (FIG. 8B). Furthermore, the discharge time was longer with an electrode width of 5 μm, even as the number of discharges increased (FIG. 8A). Measurement of each discharge count was performed by turning off the circuit after discharge and then turning it back on after the voltage had stabilized for one hour. The "L / IDT measurement" procedure described above was repeated to calculate L / IDT. The relationship between L / IDT and discharge time is shown in FIG. 8C. When L / IDT was between 1 and 20, the discharge time was long.

[0049] Example 6 In this example, n-Si / Ge was used as the first portion, EC was used as the second portion, and NaI and I ２ The second part of the battery was made of ethylene carbonate (EC) with NaI and I as the electrolyte. ２ The procedure of Example 1 was repeated, except that 0.5 mol / EC (g) and 0.05 mmol / EC (g) were used, respectively. Three sheet-type batteries were fabricated with an inter-electrode distance of 114 μm and polyiodide ion chain growth times of 0, 7, 14, and 19 days. The relationship between the short-circuit current at 80°C and L / IDT is shown in Figure 9. When L / IDT was 1 to 20, the short-circuit current was high.

[0050] Example 7 In this example, TiO ２ / Ag ２ S, DMSO as the second part, and Cp(arene)Fe and LiClO ４ A sheet-type battery was fabricated using PtTi / PEN as the first part and TiO as the second part. ２ / Ag ２ The second part was 5 mmole Cp(arene)Fe / DMSO(g) and 0.4 mole LiClO ４ The procedure of Example 1 was repeated to fabricate two sheet-type batteries with an interelectrode distance of 113 μm, except that L / DMSO (g) was used and PtTi / PEN was used as the third part. The IDT was measured before and during discharge. The relationship between the short-circuit current at 90°C and L / IDT is shown in Figure 10. When L / IDT was 1 to 20, the short-circuit current was high.

[0051] Example 8 In this example, n-Si / Ge was used as the first part, DMSO was used as the second part, and NaI and I ２ The second part was made of 0.25 mole NaI / DMSO (g) and 0.025 mole I. ２ / DMSO (g); 0.5 mole NaI / DMSO (g) and 0.05 mole I ２ / DMSO (g); or 1.0 mole NaI / DMSO (g) and 0.1 mole I ２ The procedure of Example 1 was repeated except that DMSO (g) was used, and three sheet-type batteries with an inter-electrode distance of 114 μm were fabricated. The relationship between the electric capacity at 80°C and L / IDT is shown in Figure 11. When L / IDT was 1 to 20, the electric capacity was high.

[0052] Example 9 In this example, the influence of the shortest distance between the first and third parts on the maximum discharge temperature of the thermoelectric power generation element of the present invention was examined. ２The second part was prepared by mixing 0.05 mol / L (PEGDME) and 0.5 mol / L (PEGDME) of NaI. A Ge electrode was formed on a quartz substrate as the first part, and a Pt electrode was formed on a quartz substrate as the third part, which was sputtered in a comb shape with 2 μm spacing. A 1.5 cm x 2.5 cm n-Si / Ge substrate was used as the first part, and a 1.5 x 2.5 cm FTO transparent electrode was used as the third part. The second part was sandwiched between the two electrodes, and the cell characteristics were measured while maintaining the temperature at 30°C and 80°C (Figure 12). (Diffusion distance: 48.6, electrode distance: 114 μm)

[0053] The thermoelectric power generation element of the present invention and the thermoelectric power generation module including the same can be used for batteries, small portable power generation devices, geothermal power generation, thermoelectric power generation using exhaust heat from automobiles, and thermoelectric power generation using waste heat (exhaust heat) from substations, steel furnaces, waste incinerators, etc.

[0054] 1...First part; 2...Second part; 3...Third part;

Claims

1. A thermoelectric generating element that does not require a temperature gradient, in which a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte in which a charge transport ion pair can move, and a third portion including a substance that serves as an electrode are in contact with each other in this order, the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge transport ion pair, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion, and the thermoelectric generating element does not require a temperature gradient, and satisfies the following formula (I): L / IDT=1 to 20 (I) (wherein L is the "shortest distance between the first portion and the third portion" and IDT is the "ion diffusion thickness").

2. The thermoelectric generating element according to claim 1, wherein the first portion, the second portion, and the third portion are layered.

3. The thermoelectric generating element according to claim 1, wherein the first portion, the second portion, and the third portion are positioned concentrically.

4. A thermoelectric power generation device comprising the thermoelectric power generation element according to any one of claims 1 to 3.

5. A thermoelectric battery comprising the thermoelectric generating element according to any one of claims 1 to 3.

6. A thermoelectric power generation module comprising the thermoelectric power generation element according to any one of claims 1 to 3.

7. A method for stabilizing power generation in a thermoelectric generating element that does not require a temperature gradient, in which a first portion including a semiconductor that generates thermally excited electrons and holes, a second portion including an electrolyte in which charge transporting ion pairs can move, and a third portion including a substance that serves as an electrode are in contact in this order, the valence electron potential of the semiconductor in the first portion is more positive than the redox potential of the charge transporting ion pairs, an oxidation reaction of the ion that is more easily oxidized of the two ions occurs at the interface between the first portion and the second portion, and a reduction reaction of the ion that is more easily reduced of the two ions occurs at the interface between the third portion and the second portion, characterized in that the value of L / IDT (where L is the "shortest distance between the first portion and the third portion" and IDT is the "ion diffusion thickness") is set to 1 to 20.