An ionic thermal battery electrolyte, a preparation method thereof and an ionic thermal battery

Abstract

The application discloses an ionic thermal battery electrolyte, a preparation method thereof and an ionic thermal battery, and relates to the technical field of ionic thermal batteries. The ionic thermal battery electrolyte is formed by mixing an aqueous solution containing an iodine-based redox couple and an ammonium salt; the iodine-based redox couple is composed of I ‑ and I3 ‑ ; and the concentration of the ammonium salt in the electrolyte is 4-16 mol / L. The application utilizes the strong hydration of ammonium ions and the small ion radius characteristics to effectively occupy the solvation space of I ‑ and I3 ‑ , and forcibly change the solvation sheath composition and structure of I ‑ and I3 ‑ . Due to the differences in charge density and geometric configuration of I ‑ and I3 ‑ , the reconstruction degree of the solvation sheath of the two by the high-concentration ammonium ions presents a significant differential effect, greatly increases the solvation entropy change difference in the redox reaction process, thereby improving the Seebeck coefficient and thermal response voltage, synchronously optimizing the ion transmission kinetics, and realizing the improvement of the conductivity and output power density.

Description

Technical Field

[0001] This invention relates to the field of ion thermal battery technology, and in particular to an ion thermal battery electrolyte, its preparation method, and an ion thermal battery. Background Technology

[0002] Ion-ion thermal batteries, as a novel energy storage device that directly converts thermal energy into electrical energy, have broad application prospects in the field of low-grade waste heat recovery. Among them, those based on iodine anions (I₂) are particularly promising. - ) and iodine tri-antion (I3) - Iodine-based ion thermal batteries with redox couples have attracted much attention from academia and industry due to their low cost, simple fabrication process, and environmental friendliness. However, existing iodine-based electrolyte systems still face significant challenges in practical applications. Currently, traditional iodine-based electrolytes typically employ dilute solution systems (millimolar per liter to molar per liter), where the solvation structure is in a state of natural equilibrium. In this state, I... - and I3 - The electrolyte is tightly surrounded by a large number of solvent molecules, forming a stable solvated sheath. This tight solvation structure results in a high dissociation energy barrier for ions during transport, limiting their migration rate and severely restricting the ionic conductivity of the electrolyte. More importantly, under temperature-driven conditions, the tightly bound solvation layer restricts the degrees of freedom of anions, resulting in a very small change in solvation entropy during ion migration, which directly leads to a generally low Seebeck coefficient in ion thermal batteries.

[0003] In existing technologies, improving performance often leads to a trade-off: while increasing electrolyte concentration can increase the number of charge carriers, excessively high local viscosity exacerbates ion clustering and further deteriorates ion dynamics; and simply pursuing a high Seebeck coefficient often sacrifices conductivity, resulting in the output power density of ion thermal batteries being unable to break through the bottleneck and meet the requirements of actual operating conditions.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an electrolyte for an ion thermal battery, a method for preparing the electrolyte, and an ion thermal battery, in order to solve the problems of low Seebeck coefficient and limited output power density of existing iodine-based ion thermal batteries.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides an ion-thermal battery electrolyte, wherein the ion-thermal battery electrolyte is composed of an aqueous solution containing an iodine-based redox couple and an ammonium salt; the iodine-based redox couple is composed of I... - and I3 - constitute; In the electrolyte of the ion-thermal battery, the concentration of the ammonium salt is 4 mol / L to 16 mol / L.

[0007] Optionally, the ammonium salt includes at least one of ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide.

[0008] Optionally, in the aqueous solution of the iodine-containing redox couple, the I... - The concentration of I3 is 10 mmol / L to 500 mmol / L. - The concentration ranges from 10 mmol / L to 500 mmol / L.

[0009] Optionally, the ammonium salt is ammonium fluoride, and the concentration of ammonium fluoride in the electrolyte of the ion thermal battery is 12 mol / L.

[0010] A second aspect of the present invention provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Provide an aqueous solution containing an iodine-based redox couple; the iodine-based redox couple is composed of I - and I3 - The electrolyte is prepared by adding an ammonium salt to an aqueous solution containing an iodine-based redox couple, stirring and dissolving to obtain the electrolyte for the ion-thermal battery; wherein the concentration of the ammonium salt in the electrolyte is 4 mol / L to 16 mol / L.

[0011] Optionally, the method for preparing the aqueous solution of the iodine-containing redox couple includes the following steps: Soluble alkali metal iodides and elemental iodine are added to water and dissolved to obtain an aqueous solution containing an iodine redox couple. The molar ratio of the soluble alkali metal iodide to elemental iodine is 2:1, and the ratio of elemental iodine to water is (10~500) mmol:1 L. The soluble alkali metal iodides include at least one of potassium iodide and sodium iodide.

[0012] Optionally, the ammonium salt includes at least one selected from ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide; and / or, The stirring is carried out in a constant temperature water bath at 25℃~40℃, and the stirring speed is 500 rpm~1200 rpm.

[0013] Optionally, the ammonium salt is ammonium fluoride; the concentration of ammonium fluoride in the electrolyte of the ion thermal battery is 12 mol / L.

[0014] A third aspect of the present invention provides an ion thermal battery, the ion thermal battery comprising a cold end electrode and a hot end electrode, and an electrolyte located between the cold end electrode and the hot end electrode, wherein the electrolyte comprises the ion thermal battery electrolyte of the present invention as described above, or the electrolyte comprises the ion thermal battery electrolyte prepared by the preparation method of the present invention as described above.

[0015] Optionally, the cold end electrode and the hot end electrode are made of the same material.

[0016] Beneficial effects: This invention introduces a high concentration of ammonium salt (4 mol / L to 16 mol / L), utilizing ammonium ions (NH4+). + Its strong hydration properties and small ionic radius effectively squeeze out I... - and I3 - The solvation space is forced to change I - and I3 - The solvation sheath composition and structure disrupt the native hydrogen bond network between water molecules. More importantly, due to I... - and I3 - Differences in charge density and geometry lead to significant variations in the degree of modification of the solvated sheath by high-concentration ammonium ions. This asymmetric control of the solvation environments of two anions with different charge densities greatly increases the difference in solvation entropy during the redox reaction, thus overcoming the theoretical limitations of the Seebeck coefficient in traditional iodine-based ion thermal battery electrolyte systems at the mechanistic level, and improving both the Seebeck coefficient and the thermal response voltage. Simultaneously, ion transport kinetics are optimized, resulting in a significant increase in electrolyte conductivity and an improvement in output power density.

[0017] The Seebeck coefficient of the ion-thermal battery electrolyte provided by this invention can be significantly improved to 1.396 mV K. -1 Therefore, it can impart extremely high voltage response to the battery. Simultaneously, driven by a temperature difference of 30 K, the output power density of the battery based on the ion-thermal battery electrolyte provided by this invention can reach 135.3 mW / m³. -2 This invention effectively solves the technical paradox of the difficulty in simultaneously improving the thermal response voltage and output power in existing iodine-based ion thermal batteries. It fundamentally regulates the ion transport mechanism and thermodynamic mechanism, achieving a synergistic improvement in Seebeck coefficient and output power, and providing strong technical support for the efficient capture and conversion of low-grade thermal energy. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the preparation process of the electrolyte for an ion-thermal battery in an embodiment of the present invention.

[0019] Figure 2 The graph shows the temperature response and calculated Seebeck coefficient of the ion thermal batteries assembled using the electrolytes from Example 1 and Comparative Example 1 at different temperatures.

[0020] Figure 3 The graph shows the current density and output power density of the ion thermal battery assembled using the ion thermal battery electrolyte in Example 1 at a temperature difference of 30 K.

[0021] Figure 4 The graph shows the current density and output power density of the ion thermal battery assembled using the electrolyte of Comparative Example 1 at a temperature difference of 30 K.

[0022] Figure 5 The graph shows the temperature response of the ion thermal battery assembled using the electrolyte in Example 2 at different temperatures and the calculated Seebeck coefficient.

[0023] Figure 6 The graph shows the temperature response of the ion thermal battery assembled using the electrolyte in Example 3 at different temperatures and the calculated Seebeck coefficient.

[0024] Figure 7 The graph shows the temperature response and calculated Seebeck coefficient of the ion thermal battery assembled using the electrolyte in Example 4 at different temperatures.

[0025] Figure 8 The graph shows the temperature response of the ion thermal battery assembled using the electrolyte in Example 5 at different temperatures and the calculated Seebeck coefficient.

[0026] Figure 9 The graph shows the temperature response and calculated Seebeck coefficient of the ion thermal battery assembled using the electrolyte in Comparative Example 2 at different temperatures. Detailed Implementation

[0027] This invention provides an electrolyte for an ion-thermal battery, a method for preparing the same, and the ion-thermal battery itself. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0030] Existing iodine-based ion thermal battery electrolytes exhibit low ionic conductivity and Seebeck coefficient. Current efforts to improve performance often fall into a trade-off: while increasing electrolyte concentration increases carrier numbers, excessively high local viscosity exacerbates ion clustering, further worsening ion dynamics; conversely, simply pursuing a high Seebeck coefficient often sacrifices conductivity, resulting in a persistent bottleneck in battery output power density, failing to meet practical operating conditions. Therefore, how to disrupt the existing solvation equilibrium through microscopic structural design, significantly increasing solvation entropy change while improving ion dynamics, has become a crucial scientific problem to be solved in developing high-performance iodine-based ion thermal batteries. To address this issue, this invention abandons the traditional dilute solution design approach and instead adopts a high-concentration electrolyte strategy. By introducing a specific concentration of ammonium salt into the iodine-based ion thermal battery electrolyte, the strong interionic interactions at high concentrations are utilized to forcibly alter the I0... - and I3 - The composition and structure of the solvated sheath layer are adjusted to fundamentally regulate the ion transport mechanism and thermodynamic mechanism, thereby achieving a synergistic improvement in Seebeck coefficient and output power. Specifically, this invention provides an electrolyte for an ion thermal battery, wherein the electrolyte is composed of an aqueous solution containing an iodine-based redox couple and an ammonium salt; the iodine-based redox couple is composed of I... - and I3 - constitute; In the electrolyte of the ion-thermal battery, the concentration of the ammonium salt is 4 mol / L to 16 mol / L (for example, it can be 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L, or 16 mol / L, etc.).

[0031] This invention introduces a high concentration of ammonium salt (4 mol / L to 16 mol / L), utilizing ammonium ions (NH4+). + Its strong hydration properties and small ionic radius effectively squeeze out I... - and I3 - The solvation space is forced to change I - and I3 - The solvation sheath composition and structure disrupt the native hydrogen bond network between water molecules. More importantly, due to I... - and I3 -Differences in charge density and geometry lead to significant variations in the degree of modification of the solvated sheath by high-concentration ammonium ions. This asymmetric control of the solvation environments of two anions with different charge densities greatly increases the difference in solvation entropy during the redox reaction, thus overcoming the theoretical limitations of the Seebeck coefficient in traditional iodine-based ion thermal battery electrolyte systems at the mechanistic level, and improving both the Seebeck coefficient and the thermal response voltage. Simultaneously, ion transport kinetics are optimized, resulting in a significant increase in electrolyte conductivity and an improvement in output power density.

[0032] The Seebeck coefficient of the ion-thermal battery electrolyte provided by this invention can be significantly improved to 1.396 mV K. -1 Therefore, it can impart extremely high voltage response to the battery. Simultaneously, driven by a temperature difference of 30 K, the output power density of the battery based on the ion-thermal battery electrolyte provided by this invention can reach 135.3 mW / m³. -2 This invention effectively solves the technical paradox of the difficulty in simultaneously improving the thermal response voltage and output power in existing iodine-based ion thermal batteries. It fundamentally regulates the ion transport mechanism and thermodynamic mechanism, achieving a synergistic improvement in Seebeck coefficient and output power, and providing strong technical support for the efficient capture and conversion of low-grade thermal energy.

[0033] Specifically, NH4 + Due to its small ionic radius and strong hydrogen bond donor capability, it is suitable for I - and I3 - Asymmetric desolvation occurs: I - It is a spherical monatomic ion with concentrated charge density, and is affected by NH4+. + The electric field is strong, and the solvated sheath is extremely compressed. I3 - It is a linear polyatomic ion with a relatively diffuse charge distribution and a large volume. Although its solvation layer is penetrated, it retains some structural features.

[0034] This differential reconstruction of the solvation structure due to differences in ionic configuration results in a significant difference in the migration enthalpy and migration entropy driven by temperature difference, with the Seebeck coefficient reaching 1.396 mV K. -1 The physical basis of it.

[0035] In some embodiments, the ammonium salt includes at least one of ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide.

[0036] In some embodiments, in the aqueous solution of the iodine-containing redox couple, the I... -The concentration is 10 mmol / L to 500 mmol / L (for example, it can be 10 mmol / L, 20 mmol / L, 50 mmol / L, 80 mmol / L, 100 mmol / L, 200 mmol / L, 300 mmol / L, 400 mmol / L or 500 mmol / L), the I3 - The concentration is 10 mmol / L to 500 mmol / L (for example, it can be 10 mmol / L, 20 mmol / L, 50 mmol / L, 80 mmol / L, 100 mmol / L, 200 mmol / L, 300 mmol / L, 400 mmol / L or 500 mmol / L).

[0037] In some embodiments, the ammonium salt is ammonium fluoride, and the concentration of ammonium fluoride in the ion-thermal battery electrolyte is 12 mol / L. This concentration minimizes the number of free water molecules, forcing I... - and I3 - Entering NH4 + In the dominant compact solvation structure, the maximum solvation entropy variation is achieved.

[0038] This invention also provides a method for preparing an electrolyte for an ion-thermal battery, wherein, as shown in the embodiments of the present invention... Figure 1 As shown, it includes the following steps: S1. Provide an aqueous solution containing an iodine-based redox couple; the iodine-based redox couple is composed of I... - and I3 - constitute; S2. Add ammonium salt to the aqueous solution containing the iodine-based redox couple, stir and dissolve to obtain the electrolyte of the ion thermal battery; the concentration of the ammonium salt in the electrolyte of the ion thermal battery is 4 mol / L to 16 mol / L (that is, 4 mol to 16 mol of ammonium salt is added to each liter of aqueous solution containing the iodine-based redox couple).

[0039] This invention introduces a high concentration of ammonium salt (4 mol / L to 16 mol / L), utilizing ammonium ions (NH4+). + Its strong hydration properties and small ionic radius effectively squeeze out I... - and I3 - The solvation space is forced to change I - and I3 - The solvation sheath composition and structure disrupt the native hydrogen bond network between water molecules. More importantly, due to I... - and I3 -Differences in charge density and geometry lead to significant variations in the degree of modification of the solvation sheath by high-concentration ammonium ions. This asymmetric control of the solvation environments of two anions with different charge densities greatly increases the difference in solvation entropy during the redox reaction, thus overcoming the theoretical limitations of the Seebeck coefficient in traditional iodine-based ion thermal battery electrolyte systems at the mechanistic level, and improving both the Seebeck coefficient and the thermal response voltage. Simultaneously, it optimizes ion transport kinetics, resulting in a significant increase in electrolyte conductivity and an improvement in output power density.

[0040] The Seebeck coefficient of the ion-thermal battery electrolyte provided by this invention can be significantly improved to 1.396 mV K. -1 Therefore, it can impart extremely high voltage response to the battery. Simultaneously, driven by a temperature difference of 30 K, the output power density of the battery based on the ion-thermal battery electrolyte provided by this invention can reach 135.3 mW / m³. -2 This invention effectively solves the technical paradox of the difficulty in simultaneously improving the thermal response voltage and output power in existing iodine-based ion thermal batteries. It fundamentally regulates the ion transport mechanism and thermodynamic mechanism, achieving a synergistic improvement in Seebeck coefficient and output power, and providing strong technical support for the efficient capture and conversion of low-grade thermal energy.

[0041] In step S1, in some embodiments, the method for preparing the aqueous solution of the iodine-containing redox couple includes the following steps: Soluble alkali metal iodides and elemental iodine are added to water and dissolved to obtain a redox couple containing iodine groups (I0.05). - and I3 - ( ) aqueous solution; The molar ratio of the soluble alkali metal iodide to elemental iodine is 2:1, and the ratio of elemental iodine to water is (10~500) mmol: 1 L, for example, 10 mmol: 1 L, 20 mmol: 1 L, 50 mmol: 1 L, 80 mmol: 1 L, 100 mmol: 1 L, 200 mmol: 1 L, 300 mmol: 1 L, 400 mmol: 1 L, or 500 mmol: 1 L, etc.

[0042] By adding soluble alkali metal iodides and elemental iodine to water, a reaction occurs, producing I3. - (i.e. I - + I2=I 3- ), thus forming a structure containing I - and I3 - An aqueous solution of soluble alkali metal iodide and elemental iodine. When the molar ratio of soluble alkali metal iodide to elemental iodine is 2:1, the reaction can produce I₃.- Meanwhile, there is still unreacted I - Thus forming a structure containing I - and I3 - Aqueous solution.

[0043] In some embodiments, the soluble alkali metal iodide includes at least one of potassium iodide and sodium iodide, but is not limited thereto.

[0044] In step S2, in some embodiments, the ammonium salt includes at least one of ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide.

[0045] In some embodiments, the stirring is carried out in a constant temperature water bath at 25°C to 40°C (e.g., 25°C, 30°C, 35°C, or 40°C), and the stirring speed is 500 rpm to 1200 rpm (e.g., 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm). When the concentration of ammonium salt added is high, the solution viscosity will increase sharply after addition. By combining the 25°C to 40°C temperature with high-speed stirring, the ammonium salt can be completely dissolved to form a homogeneous and stable solution, avoiding local crystallization or the formation of undissociated ion clusters, thereby ensuring that the electrolyte has excellent ion transport kinetics performance.

[0046] In some embodiments, the ammonium salt is ammonium fluoride; the concentration of ammonium fluoride in the ion-thermal battery electrolyte is 12 mol / L. This concentration minimizes the number of free water molecules, forcing I... - and I3 - Entering NH4 + In the dominant compact solvation structure, the maximum solvation entropy variation is achieved.

[0047] This invention also provides an ion thermal battery, which includes a cold end electrode and a hot end electrode, and an electrolyte located between the cold end electrode and the hot end electrode. The electrolyte includes the ion thermal battery electrolyte of this invention as described above, or the electrolyte includes the ion thermal battery electrolyte prepared by the preparation method of this invention as described above.

[0048] In some embodiments, the cold end electrode and the hot end electrode are made of the same material.

[0049] In some embodiments, both the cold-end electrode and the hot-end electrode are platinum electrodes or carbon paper electrodes.

[0050] The present invention will be further described below through specific embodiments.

[0051] In the following embodiments, unless otherwise specified, the raw materials and equipment used are all commercially available products.

[0052] Example 1 This embodiment provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - Aqueous solution (wherein I) - and I3 - The concentrations were all 50 mmol / L. In the above-mentioned I - and I3 - Add 12 mol / L ammonium fluoride powder (i.e., the concentration of ammonium fluoride in the ion thermal battery electrolyte is 12 mol / L) to the aqueous solution, and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let it stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0053] Example 2 This embodiment provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - Aqueous solution (wherein I) - and I3 - The concentrations were all 50 mmol / L. In the above-mentioned I - and I3 - Add 8 mol / L ammonium fluoride powder to the aqueous solution (i.e., the concentration of ammonium fluoride in the ion thermal battery electrolyte is 8 mol / L), and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0054] Example 3 Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - Aqueous solution (wherein I) - and I3 - The concentrations were all 50 mmol / L. In the above-mentioned I- and I3 - Add 16 mol / L ammonium fluoride powder to the aqueous solution (i.e., the concentration of ammonium fluoride in the ion thermal battery electrolyte is 16 mol / L), and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0055] Example 4 Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - Aqueous solution (wherein I) - and I3 - The concentrations were all 50 mmol / L. In the above-mentioned I - and I3 - Add 12 mol / L ammonium chloride powder to the aqueous solution (i.e., the concentration of ammonium chloride in the ion thermal battery electrolyte is 12 mol / L), and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let it stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0056] Example 5 This embodiment provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Add 41.5 g of potassium iodide and 31.7 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - An aqueous solution containing 500 mmol / L I - and 500 mmol / L of I3 - ); In the above-mentioned I - and I3 - Add 12 mol / L ammonium fluoride powder (i.e., the concentration of ammonium fluoride in the ion thermal battery electrolyte is 12 mol / L) to the aqueous solution, and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let it stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0057] Comparative Example 1 This comparative example provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water and stir continuously until the solution is clear and free of precipitate to obtain the electrolyte for the ion-thermal battery, which contains 50 mmol / L of I₂. - and 50 mmol / L I3 - .

[0058] Comparative Example 2 This comparative example provides a method for preparing an electrolyte for an ion-thermal battery, comprising the following steps: Add 4.15 g of potassium iodide and 3.17 g of elemental iodine to 250 mL of deionized water, and stir continuously until the solution is clear and free of precipitate, to obtain a solution containing I. - and I3 - An aqueous solution containing 50 mmol / L I - and 50 mmol / L I3 - ); In the above-mentioned I - and I3 - Add 2 mol / L ammonium fluoride powder to the aqueous solution (i.e., the concentration of ammonium fluoride in the ion thermal battery electrolyte is 2 mol / L), and stir rapidly at 1000 rpm in a constant temperature water bath at 25℃ until the powder dissolves. Let it stand for 6 hours to obtain a stable ion thermal battery electrolyte.

[0059] test: (1) The ion thermal battery electrolyte in Example 1 and the ion thermal battery electrolyte in Comparative Example 1 (i.e. containing 50 mM I - / I3 - Tested using an aqueous solution: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. The ion-thermal battery electrolyte from Example 1 and the ion-thermal battery electrolyte from Comparative Example 1 (i.e., containing 50 mM I) were used, respectively. - / I3 - An aqueous solution was used to assemble an ion-thermal battery, and its electrochemical performance was tested at different temperatures. The temperature response at different temperatures and the calculated Seebeck coefficients are shown below. Figure 2 As shown. It can be seen that the Seebeck coefficient (Si) of the ion-thermal battery assembled using the ion-thermal battery electrolyte in Example 1 is... e It can reach 1.396 mV K -1 The electrolyte used in Comparative Example 1 (i.e., containing 50 mM I) was used instead. - / I3 - The Seebeck coefficient of the ion thermal battery assembled in aqueous solution is only 0.660 mV K. -1Furthermore, the output power density of the ion-thermal batteries assembled using the two electrolytes mentioned above was tested, and the results are as follows: Figure 3 and Figure 4 As shown, the ion thermal battery assembled using the ion thermal battery electrolyte in Example 1 can achieve an output power density (i.e., discharge power density) of 135.3 mW / m³ at a temperature difference of 30 K. -2 ( Figure 3 ), while using the ion thermal battery electrolyte in Comparative Example 1 (i.e. containing 50 mM I - / I3 - The ion thermal battery assembled from an aqueous solution had an output power density of only 9.8 mW / m³ at a temperature difference of 30 K. -2 ( Figure 4 ).

[0060] (2) The electrolyte of the ion thermal battery in Example 2 was tested: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. Using the ion-thermal battery electrolyte from Example 2, an ion-thermal battery was assembled and its electrochemical performance was tested. The results are as follows: Figure 5 As shown, under the same test conditions, the Seebeck coefficient of the ion thermal battery can reach 1.178 mV K. -1 Similar to the results in Example 1, it still significantly surpasses the results containing 50 mM I - / I3 - The excellent electrochemical performance of its aqueous solution.

[0061] (3) The electrolyte of the ion thermal battery in Example 3 was tested: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. Using the ion-thermal battery electrolyte from Example 3, an ion-thermal battery was assembled and its electrochemical performance was tested. The results are as follows: Figure 6 As shown, under the same test conditions, the Seebeck coefficient of the ion thermal battery can reach 0.965 mV K. -1 Similar to the results in Example 1, it still significantly surpasses the results containing 50 mM I - / I3 - The excellent electrochemical performance of its aqueous solution.

[0062] (4) The electrolyte of the ion thermal battery in Example 4 was tested: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. Using the ion-thermal battery electrolyte from Example 4, an ion-thermal battery was assembled and its electrochemical performance was tested. The results are as follows: Figure 7 As shown, under the same test conditions, the Seebeck coefficient of the ion thermal battery can reach 1.250 mV K. -1 Similar to the results in Example 1, it still significantly surpasses the results containing 50 mM I - / I3 - The excellent electrochemical performance of its aqueous solution.

[0063] (5) The electrolyte of the ion thermal battery in Example 5 was tested: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. Using the ion-thermal battery electrolyte from Example 5, an ion-thermal battery was assembled and its electrochemical performance was tested. The results are as follows: Figure 8 As shown, under the same test conditions, the Seebeck coefficient of the ion thermal battery can reach 1.070 mV K. -1 Similar to the results in Example 1, it still significantly surpasses I. - / I3 - Excellent electrochemical properties of aqueous solutions.

[0064] (6) The electrolyte of the ion thermal battery in Comparative Example 2 was tested: Two platinum plates were used as the cold-end electrode and the hot-end electrode, respectively. The hot-end electrode was heated to different temperatures on a heating plate, while the cold-end electrode was maintained at room temperature. Using the ion-thermal battery electrolyte from Comparative Example 2, an ion-thermal battery was assembled and its electrochemical performance was tested. The results are as follows: Figure 9 As shown, under the same test conditions, the Seebeck coefficient of the ion thermal battery is only 0.630 mV K. -1 The Seebeck coefficient decreased significantly because, under low concentration (2 mol / L) ammonium fluoride conditions, the large number of free water molecules in the solution ensured that the added ammonium fluoride ions were in a fully hydrated state, and their large hydrated layer could not effectively displace or compress I. - / I3 - The original solvated sheath layer, instead, acts as an additional inert charge carrier, increasing I in the solution. - / I3 - The collision frequency and frictional resistance during migration lead to an increase in the apparent migration activation energy of ions; simultaneously, due to insufficient ionic strength, the solution microenvironment remains dominated by water molecules. - / I3 -The solvation environments remained similar, failing to produce a differentiated reconstruction effect. Consequently, the migration entropy difference between the two under temperature-driven conditions was not effectively widened or was even diluted and offset, ultimately leading to a decrease in the Seebeck coefficient instead of an increase. This also indirectly confirms the necessity of setting the ammonium salt concentration in the range of 4 mol / L to 16 mol / L and using high-concentration ammonium salt to force reconstruction of the solvation structure to achieve a performance breakthrough.

[0065] The above results demonstrate that the key to forcibly altering the electrolyte's microenvironment using ultra-high concentrations of ammonium salts ranging from 4 mol / L to 16 mol / L lies in leveraging the strong hydration effect of ammonium ions on I... - and I3 - These two configurations undergo asymmetric (differentiated) solvation sheath reconstruction with anions of drastically different charge densities. This difference in the degree of solvation structural change due to ionic morphology is the fundamental reason for the huge difference in solvation entropy, thus breaking through the theoretical limitations of the Seebeck coefficient. Furthermore, the addition of ammonium salts has a concentration threshold (4 mol / L). Only when the concentration exceeds this threshold and enters the high-concentration electrolyte range can the free hydrogen bond network between water molecules be disrupted, achieving a shift from a "solvent-separated" to a "direct ion contact" transport mechanism. This leads to a simultaneous increase in both the Seebeck coefficient and conductivity, completely avoiding the risk of performance degradation at low concentrations (e.g., 2 mol / L).

[0066] In summary, this invention provides an electrolyte for an ion-thermal battery, a method for preparing the electrolyte, and the ion-thermal battery itself. The invention utilizes ammonium ions (NH4+) by introducing a high concentration of ammonium salt (4 mol / L to 16 mol / L). + Its strong hydration properties and small ionic radius effectively squeeze out I... - and I3 - The solvation space is forced to change I - and I3 - The solvation sheath composition and structure disrupt the native hydrogen bond network between water molecules. More importantly, due to I... - and I3 - There are differences in charge density and geometry; high concentrations of NH4 + The degree of modification to the solvation sheath of the two batteries exhibits a significantly different effect. This asymmetric control of the solvation environments of two anions with different charge densities greatly increases the difference in solvation entropy during the redox reaction process, thus breaking through the theoretical limitation of the Seebeck coefficient in the electrode liquid system of traditional iodine-based ion thermal batteries at the mechanistic level, and improving the Seebeck coefficient and thermal response voltage. At the same time, it also optimizes ion transport kinetics, achieving a significant improvement in electrolyte conductivity and thus increasing the output power density.

[0067] The Seebeck coefficient of the ion-thermal battery electrolyte provided by this invention can be significantly improved to 1.396 mV K. -1 Therefore, it can impart extremely high voltage response to the battery. Simultaneously, driven by a temperature difference of 30 K, the output power density of the battery based on the ion-thermal battery electrolyte provided by this invention can reach 135.3 mW / m³. -2 This invention effectively solves the technical paradox of the difficulty in simultaneously improving the thermal response voltage and output power in existing iodine-based ion thermal batteries. It fundamentally regulates the ion transport mechanism and thermodynamic mechanism, achieving a synergistic improvement in Seebeck coefficient and output power, and providing strong technical support for the efficient capture and conversion of low-grade thermal energy.

[0068] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An electrolyte for an ion-thermal battery, characterized in that, The electrolyte of the ion thermal battery is composed of an aqueous solution containing an iodine-based redox couple and an ammonium salt; the iodine-based redox couple is composed of I... - and I3 - constitute; In the electrolyte of the ion-thermal battery, the concentration of the ammonium salt is 4 mol / L to 16 mol / L.

2. The electrolyte for an ion-thermal battery according to claim 1, characterized in that, The ammonium salt includes at least one of ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide.

3. The electrolyte for an ion-thermal battery according to claim 1, characterized in that, In the aqueous solution of the iodine-containing redox couple, the I - The concentration of I3 is 10 mmol / L to 500 mmol / L. - The concentration ranges from 10 mmol / L to 500 mmol / L.

4. The electrolyte for an ion-thermal battery according to claim 1, characterized in that, The ammonium salt is ammonium fluoride, and the concentration of ammonium fluoride in the electrolyte of the ion thermal battery is 12 mol / L.

5. A method for preparing an electrolyte for an ion-thermal battery, characterized in that, Includes the following steps: Provide an aqueous solution containing an iodine-based redox couple; the iodine-based redox couple is composed of I - and I3 - constitute; An ammonium salt is added to the aqueous solution containing the iodine-based redox couple, and the solution is stirred and dissolved to obtain the electrolyte for the ion-thermal battery; the concentration of the ammonium salt in the electrolyte is 4 mol / L to 16 mol / L.

6. The method for preparing the electrolyte for an ion-thermal battery according to claim 5, characterized in that, The method for preparing the aqueous solution containing the iodine-containing redox couple includes the following steps: Soluble alkali metal iodides and elemental iodine are added to water and dissolved to obtain an aqueous solution containing an iodine redox couple. The molar ratio of the soluble alkali metal iodide to elemental iodine is 2:1, and the ratio of elemental iodine to water is (10~500) mmol:1 L. The soluble alkali metal iodides include at least one of potassium iodide and sodium iodide.

7. The method for preparing the electrolyte for an ion-thermal battery according to claim 5, characterized in that, The ammonium salt includes at least one selected from ammonium fluoride, ammonium bromide, ammonium chloride, and ammonium iodide; and / or, The stirring is carried out in a constant temperature water bath at 25℃~40℃, and the stirring speed is 500 rpm~1200 rpm.

8. The method for preparing the electrolyte for an ion-thermal battery according to claim 5, characterized in that, The ammonium salt is ammonium fluoride; the concentration of ammonium fluoride in the electrolyte of the ion thermal battery is 12 mol / L.

9. An ion thermal battery, the ion thermal battery comprising a cold-end electrode and a hot-end electrode, and an electrolyte located between the cold-end electrode and the hot-end electrode, characterized in that, The electrolyte includes the ion thermal battery electrolyte according to any one of claims 1-4, or the electrolyte includes the ion thermal battery electrolyte prepared by the preparation method according to any one of claims 5-8.

10. The ion thermal battery according to claim 9, characterized in that, The cold end electrode and the hot end electrode are made of the same material.

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