A high-voltage fluorine-ion thermal battery with a dual-electrolyte structure and its preparation method

Abstract

This invention belongs to the field of thermal battery technology and discloses a high-voltage fluoride-ion thermal battery with a dual-electrolyte structure and its preparation method. The battery structure includes a composite positive electrode layer, a fluoride-ion solid electrolyte layer, a molten fluoride salt electrolyte layer, and a negative electrode layer. The composite positive electrode layer is a mixture of transition metal fluoride positive electrode active material, fluoride-ion solid electrolyte, and conductive carbon material. The fluoride-ion solid electrolyte layer consists of a fluoride-ion solid electrolyte, and the molten fluoride salt electrolyte layer consists of a mixture of molten fluoride salt and a ceramic support. In the composite positive electrode layer, the fluoride-ion solid electrolyte forms a fluoride ion transport channel for the positive electrode. The fluoride-ion solid electrolyte layer both transfers fluoride ions and blocks the leaching reaction between the positive electrode layer and the molten fluoride salt electrolyte layer. This invention, through the synergistic effect of the fluoride-ion solid electrolyte and the molten fluoride salt electrolyte layer, greatly improves the utilization rate of the positive electrode active material, contributing to meeting the demand for high-voltage, high-energy-density, and small-volume thermal batteries.

Description

Technical Field

[0001] This invention relates to the field of thermal battery technology, specifically to a high-voltage fluorine-ion thermal battery with a dual-electrolyte structure and its preparation method. Background Technology

[0002] Based on their working principle, thermal batteries can be divided into cationic thermal batteries and anionic thermal batteries. A cationic thermal battery is a type of primary power supply that uses molten salt as the electrolyte and is activated by an external heat source. It features room temperature circuit breaking, high-temperature activation, long-term storage, low self-discharge rate, rapid start-up, and high reliability, and is widely used in spacecraft, rocket ignition systems, emergency rescue equipment, deep well drilling, and other unattended or one-time emergency power supply devices. Lithium-ion thermal batteries are the most representative of cationic thermal batteries. According to the cathode material, they mainly include sulfide, chloride, and fluoride cathode material systems. Sulfide cathodes are relatively mature, with stable operating voltage and high energy density. However, their operating voltage is usually below 2V, making it difficult to meet the equipment's requirements for instantaneous high-power start-up, high specific energy output, and small size. Chloride cathodes have certain reactivity, but suffer from insufficient thermal stability and numerous high-temperature side reactions. In contrast, transition metal fluorides have high reaction potential and high theoretical energy density, meeting the equipment's requirements for instantaneous high-power start-up and high specific energy output, and are considered high-energy-density thermal batteries with application potential. However, the discharge principle of existing lithium-ion batteries using transition metal fluorides as cathode materials is based on Li +Insulating products such as LiF migrate towards the positive electrode side. These products tend to accumulate on the surface of the positive electrode active material, increasing internal resistance and preventing the active material from fully releasing its capacity, resulting in low utilization. Therefore, anion thermal batteries have been developed. The most representative of these is the fluorine-ion thermal battery (FITB), as seen in the following publications: Electrochimica Acta 2024, 508, 145263; Chinese Patent Publication No. CN111354954A; Chinese Patent Publication No. CN117239162A; Journal of Materials Chemistry A 2025, 13, 29528. It is a novel thermal battery system that typically uses a transition metal fluoride as the positive electrode and a molten fluoride salt as the electrolyte. Fluorine ions migrate between the positive and negative electrodes as the main charge carriers to achieve high-temperature discharge reactions. Compared with lithium-ion thermal batteries, fluorine-ion thermal batteries achieve energy conversion through two reactions: defluorination of the transition metal fluoride positive electrode and fluorination of the negative electrode metal. The current battery structure consists of a transition metal fluoride cathode, a molten fluoride salt electrolyte, a molten fluoride salt electrolyte / binder layer, and a lanthanum or calcium metal anode. However, this structure limits the use of a metallic Li anode. Furthermore, this type of structure easily leads to wetting of the molten fluoride salt electrolyte with the cathode active material, resulting in cathode material loss and low utilization. Therefore, developing a truly universal fluoride-ion thermal battery structure has significant theoretical and practical value. Summary of the Invention

[0003] This invention proposes a high-voltage fluoride-ion thermal battery with a dual-electrolyte structure and its preparation method, constructing a novel fluoride-ion thermal battery system. The battery system comprises a composite positive electrode layer, a fluoride-ion solid electrolyte layer, a molten fluoride salt electrolyte layer, and a negative electrode layer. The composite positive electrode layer is a mixture of transition metal fluoride positive electrode active material, a fluoride-ion solid electrolyte, and a conductive carbon material. The fluoride-ion solid electrolyte layer consists of a fluoride-ion solid electrolyte, and the molten fluoride salt electrolyte layer consists of a mixture of molten fluoride salt and a ceramic support. The negative electrode layer can be one of Li-B alloy, metallic La, metallic Mg, or metallic Ca. The fluoride-ion solid electrolyte can be LaF3-based, alkaline earth metal fluoride-based, PbF2-based, SnF2-based, or a composite fluoride-type fluoride-ion conductor. In the composite positive electrode layer, the fluoride-ion solid electrolyte forms the positive electrode and constructs a fluoride ion transport channel; the fluoride-ion solid electrolyte layer both transmits fluoride ions and blocks contact between the positive electrode layer and the molten fluoride salt electrolyte layer. This novel fluorine-ion battery not only breaks the limitations of traditional fluorine-ion batteries in using lithium metal anodes, but also overcomes the unavoidable wetting reaction between molten fluorine ion salt electrolyte and positive electrode active material in traditional fluorine-ion batteries. It can greatly improve the utilization rate of positive electrode active material and help meet the demand for high-voltage, high-energy-density, and small-volume thermal batteries.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-voltage fluorine-ion thermal battery with a dual-electrolyte structure includes a composite positive electrode layer, a fluorine-ion solid electrolyte layer, a molten fluoride salt electrolyte layer, and a negative electrode layer arranged sequentially.

[0005] The composite positive electrode layer, the fluoride ion solid electrolyte layer, and the molten fluoride salt electrolyte layer are all formed by pressing solid powder, and the negative electrode layer is composed of one of the following: metal sheet, metal powder, or metal alloy sheet.

[0006] The composite positive electrode layer comprises a transition metal fluoride, a fluoride ion solid electrolyte, and a conductive carbon material; the mass ratio of each component is: transition metal fluoride : fluoride ion solid electrolyte : conductive carbon material = (20-80) : (10-70) : (1-20).

[0007] The transition metal fluoride is one or more of CuF2, NiF2, FeF3, BiF3, CoF2, and MnF3; the conductive carbon material is one or more of carbon nanotubes, acetylene black, conductive graphite, and graphene; and the fluoride ion solid electrolyte is one or more of LaF3-based, alkaline earth metal fluoride-based, PbF2-based, SnF2-based, or composite fluoride solid electrolytes.

[0008] The fluoride ion solid electrolyte layer is disposed between the composite positive electrode layer and the molten fluoride salt electrolyte layer; the fluoride ion solid electrolyte is one or more of LaF3-based, alkaline earth metal fluoride-based, PbF2-based, SnF2-based, or composite fluoride solid electrolytes.

[0009] The molten fluoride electrolyte layer comprises molten fluoride and a ceramic proppant; the mass fraction of the ceramic proppant in the molten fluoride electrolyte layer is 10 wt.% to 70 wt.%; the molten fluoride is one or more of LiF, NaF, KF, and CsF; and the ceramic proppant is one or more of MgO, Al2O3, ZrO2, and SiO2.

[0010] The negative electrode layer is an active metal or alloy that can undergo an electrochemical reaction with fluoride ions; the negative electrode material of the negative electrode layer is one of Li-B alloy, metal La, metal Mg, and metal Ca.

[0011] A method for preparing a high-voltage fluorine-ion thermal battery with a dual-electrolyte structure includes the following steps: Step 1, constructing a layered battery structure: In the compression mold, add nickel foam, composite positive electrode powder, fluoride ion solid electrolyte, molten fluoride salt electrolyte powder and negative electrode material in sequence to form a layered structure in which the composite positive electrode layer, fluoride ion solid electrolyte layer, molten fluoride salt electrolyte layer and negative electrode layer are stacked in sequence. Step 2, pressing and molding: The above-mentioned layered structure powder is pressed to obtain a fluorine-ion thermal battery cell with a dual electrolyte structure; Step 3, High-temperature activation discharge: The fluorine-ion thermal battery cell with dual electrolyte structure is heated to the working temperature of the molten fluorine salt electrolyte layer, so that the molten fluorine salt electrolyte melts and forms an ion transport channel, and then a constant current discharge test is performed.

[0012] In step 1, the mass of the fluoride ion solid electrolyte powder in the fluoride ion solid electrolyte layer is 10 to 50 wt. of the mass of the composite positive electrode layer.

[0013] In step 2, the pressing process includes: first holding under a pre-pressure of 1t to 5t for 0.5 min to 5 min, and then holding under an additional pressure of 15t to 20t for 5 min to 20 min; in step 3, the temperature of the high-temperature activation discharge is 500℃ to 600℃.

[0014] When the structure of a high-voltage fluorine-ion thermal battery with a dual electrolyte structure is: positive electrode (CuF2: La 0.95 Ba 0.05 F 2.95 : CNTs= 3:6:1)|La 0.95 Ba 0.05 F 2.95 When using solid electrolytes (LiF-NaF-KF molten salt electrolytes) and Li-B alloy anodes, the current density is 1000 mA·g at 500℃. -1 With a cutoff voltage of 1.5V, the battery discharge specific capacity reaches 478.05 mAh·g. -1 .

[0015] The present invention has the following technical effects: (1) This invention constructs a dual electrolyte structure through the synergistic effect of solid fluoride ion electrolyte and molten fluoride salt electrolyte, thereby achieving simultaneous optimization of interface stability control and high-temperature rapid ion conduction.

[0016] (2) The fluoride ion solid electrolyte layer provided in this invention can maintain fluoride ion transport while blocking the direct leaching of the positive electrode active material by the molten fluoride salt electrolyte.

[0017] (3) The fluoride ion solid electrolyte layer provided in this invention can promote the migration of fluoride ions during discharge, while hindering the movement of cations to the positive electrode, thereby avoiding the occurrence of side reactions.

[0018] (4) The present invention introduces a fluoride ion solid electrolyte into the inside of the positive electrode, so that it can act as a fluoride ion conductor in the positive electrode and cooperate with the electron conduction network constructed by the conductive carbon material to improve the utilization rate of the positive electrode active material. Attached Figure Description

[0019] Figure 1 A schematic diagram illustrating the working mechanism of a high-temperature activated thermal battery with a solid fluoride ion conductor / molten fluoride salt dual electrolyte structure. Figure 2 A single-cell thermal battery with a solid fluoride ion conductor / molten fluoride salt dual electrolyte structure operates at a current density of 1000 mA·g. -1 The following is a diagram showing the discharge test results; Figure 3 For traditional single-cell thermal batteries at a current density of 1000 mA·g -1 The following is a diagram showing the discharge test results. Detailed Implementation

[0020] The present invention will be further described in detail below through embodiments, but is not limited to the embodiments.

[0021] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0022] Example 1 Preparation of composite cathode powder: Weigh CuF2, La 0.95 Ba 0.05 F 2.95 The powder was ground thoroughly in an agate mortar with carbon nanotubes in a mass ratio of 3:6:1 to obtain a composite cathode powder. To prepare molten fluoride electrolyte powder, LiF, NaF, and KF were mixed to obtain LiF-NaF-KF molten fluoride salt powder. Subsequently, MgO ceramic support was added to achieve a MgO mass fraction of 50 wt.% in the molten fluoride electrolyte layer. The mixture was then thoroughly ground and mixed to obtain LiF-NaF-KF / MgO molten fluoride electrolyte powder. To construct the layered battery structure, nickel foam, 0.3 g of the composite cathode powder, and 0.15 g of La were sequentially added to a 16 mm diameter die. 0.95 Ba 0.05 F 2.95 Fluoride ion solid electrolyte, 0.5 g LiF-NaF-KF / MgO molten fluoride salt electrolyte powder, and Li-B alloy anode material were used to form a layered structure consisting of nickel foam, a composite positive electrode layer, a fluoride ion solid electrolyte layer, a molten fluoride salt electrolyte layer, and an anode layer stacked sequentially. The layered powder was pressed, first held at a pre-compression of 1 t for 0.5 min, and then held at a pressure of 10 t for 5 min; a single-cell thermal battery with a solid fluoride ion / molten fluoride salt dual electrolyte structure was obtained. The obtained battery cell was heated to 500 °C and subjected to 1000 mA·g -1 Discharge tests were conducted under constant current conditions, and the results are as follows: Figure 2 As shown.

[0023] Experimental results show that, under a cutoff voltage of 1.5V, the battery discharge specific capacity reaches 478.05 mAh·g. -1 This result indicates that La 0.95 Ba 0.05 F 2.95 The dual electrolyte structure, consisting of a fluoride ion solid electrolyte and a LiF-NaF-KF molten fluoride salt electrolyte, can maintain effective ion transport under high current density conditions and achieve continuous high power output.

[0024] Comparative Example 1 Preparation of composite cathode powder: Weigh CuF2, La 0.95 Ba 0.05 F 2.95 The powders were ground thoroughly in an agate mortar with carbon nanotubes in a mass ratio of 3:6:1 to obtain composite cathode powder. Molten fluoride electrolyte powder was prepared by mixing LiF, NaF, and KF to obtain LiF-NaF-KF molten fluoride electrolyte powder. Subsequently, MgO ceramic support was added to achieve a MgO mass fraction of 50 wt.% in the molten fluoride electrolyte layer. The mixture was then thoroughly ground and mixed to obtain LiF-NaF-KF / MgO molten fluoride electrolyte powder. A layered battery structure was constructed by sequentially adding nickel foam, 0.3 g of composite cathode powder, 0.5 g of LiF-NaF-KF / MgO molten fluoride electrolyte powder, and Li-B alloy anode material to a 16 mm diameter die, forming a layered structure with nickel foam, a composite cathode layer, a molten fluoride electrolyte layer, and an anode layer stacked sequentially. The layered powder was pressed, first under a pre-compression of 1 t for 0.5 min, then under an additional pressure of 10 t for 5 min; this yielded a single thermal cell. The resulting cell was heated to 500 °C and subjected to a 1000 mA g-pressure test. -1 Discharge tests were conducted under constant current conditions, and the results are as follows: Figure 3 As shown, the experimental results indicate that, under a cutoff voltage of 1.5V, the battery discharge specific capacity reaches 393.75 mAh·g. -1 .

[0025] Compared to Comparative Example 1, the battery discharge specific capacity increased from 393.75 mAh·g after introducing a fluoride ion solid electrolyte layer in Example 1. -1 Increased to 478.05 mAh·g -1 This indicates that setting a fluoride ion solid electrolyte layer can effectively improve ion transport and interface stability at the positive electrode / molten fluoride salt electrolyte interface, and improve the utilization rate of positive electrode active material.

[0026] Comparative Example 2 Same as Example 1, except that: The composite cathode has the following composition: CuF2:LiF-NaF-KF:carbon nanotubes = 3:6:1, that is, LiF-NaF-KF molten fluoride salt replaces the La inside the composite cathode in Example 1. 0.95 Ba 0.05 F 2.95 The fluoride ion solid electrolyte was prepared using the same methods and under the same testing conditions as in Example 1.

[0027] The resulting battery cell was heated to 500 °C and subjected to a 1000 mA g test. -1 Discharge tests were conducted under constant current conditions. The experimental results showed that, with a cutoff voltage of 1.5V, the battery's discharge specific capacity reached 428.12 mAh·g. -1 .

[0028] Compared to Comparative Example 2, Example 1 introduced La into the composite cathode. 0.95 Ba 0.05 F 2.95 After using a fluoride-ion solid electrolyte, the battery's discharge specific capacity increased from 428.12 mAh·g. -1 Increased to 478.05 mAh·g -1 This result indicates that, compared to directly introducing molten fluoride salts into the positive electrode, using a fluoride-ion solid electrolyte as the internal ion-conducting component of the positive electrode is more conducive to constructing a stable F-type cathode. - The transmission channel reduces the direct leaching of molten salt onto the positive electrode active material and the impact of side reactions, thereby improving the utilization rate of the positive electrode active material and the battery discharge performance.

[0029] Example 2 Same as Example 1, except that: (1) The active material in the positive electrode is NiF2, and the other methods are the same.

[0030] The results show that using NiF2 as the positive electrode active material results in a lower operating voltage.

[0031] Example 3 Same as Example 1, except that: (1) The active material in the positive electrode is FeF3, and the other methods are the same.

[0032] The results show that using FeF3 as the positive electrode active material results in a lower operating voltage.

[0033] Example 4 Same as Example 1, except that: (1) The active material in the positive electrode is MnF3, and the other methods are the same.

[0034] The results show that using MnF3 as the positive electrode active material results in a lower discharge specific capacity.

[0035] Example 5 Same as Example 1, except that: (1) The active material in the positive electrode is CoF2, and the other methods are the same.

[0036] The results show that using CoF2 as the positive electrode active material results in a lower operating voltage.

[0037] Example 6 Same as Example 1, except that: (1) The active material in the positive electrode is BiF3, and the other methods are the same.

[0038] The results show that using BiF3 as the positive electrode active material results in a lower operating voltage.

[0039] Example 7 Same as Example 1, except that: (1) The conductive agent in the positive electrode is acetylene black, and the other methods are the same.

[0040] The results show that its electron conduction effect in the positive electrode is weaker than that of carbon nanotubes.

[0041] Example 8 Same as Example 1, except that: (1) The conductive agent in the positive electrode is conductive graphite, and the other methods are the same.

[0042] The results show that its electron conduction effect in the positive electrode is weaker than that of carbon nanotubes.

[0043] Example 9 (1) The conductive agent in the positive electrode is graphene, and the other methods are the same.

[0044] The results show that its electron conduction effect in the positive electrode is weaker than that of carbon nanotubes.

[0045] Example 10 Same as Example 1, except that: (1) The fluoride ion solid electrolyte is La 1-x Sr x F 3-x The other methods are the same.

[0046] The results show that La 1-x Sr x F 3-x The fluoride ion conduction and interface modulation effects in this system are not as good as those of La. 1-x Ba x F 3-x .

[0047] Example 11 Same as Example 1, except that: (1) The fluoride ion solid electrolyte is La 1-x Ca x F 3-x The other methods are the same.

[0048] The results show that La 1-x Ca x F 3-x The fluoride ion conduction and interface modulation effects in this system are not as good as those of La. 1-x Ba x F 3-x .

[0049] Example 12 Same as Example 1, except that: (1) The fluoride ion solid electrolyte is La 1-x Ce x F3, the other methods are the same.

[0050] The results show that La 1-x Ce x F3's effects on fluoride ion transport and interface regulation in this system are not as good as those of La. 1-x Ba x F 3-x .

[0051] Example 13 Same as Example 1, except that: (1) The fluoride ion solid electrolyte is La 1-x Sm x F3, the other methods are the same.

[0052] The results show that La 1-x Sm x F3's effects on fluoride ion transport and interface regulation in this system are not as good as those of La. 1-x Ba x F 3-x .

[0053] Example 14 Same as Example 1, except that: (1) The composition of the molten fluoride salt electrolyte powder is LiF, NaF, KF and CsF, and the other components are the same.

[0054] The results show that the LiF-NaF-KF-CsF quaternary molten fluoride salt system can also form ion transport channels after high-temperature activation, and together with the fluoride ion solid electrolyte, it constitutes a solid-liquid dual electrolyte structure.

[0055] Example 15 Same as Example 1, except that: (1) The composition of the molten fluoride salt electrolyte powder is LiF, NaF and CsF, and the other components are the same.

[0056] The results show that the LiF-NaF-CsF quaternary molten fluoride salt system can also form ion transport channels after high-temperature activation, and together with the fluoride ion solid electrolyte, it constitutes a solid-liquid dual electrolyte structure. Example 16 Same as Example 1, except that: (1) The composition of the molten fluoride salt electrolyte powder is LiF, KF and CsF, and the other components are the same.

[0057] The results show that the LiF-KF-CsF quaternary molten fluoride salt system can also form ion transport channels after high-temperature activation, and together with the fluoride ion solid electrolyte, it constitutes a solid-liquid dual electrolyte structure. Example 17 Same as Example 1, except that: (1) The composition of the molten fluoride salt electrolyte powder is NaF, KF and CsF, and the other components are the same.

[0058] The results show that the NaF-KF-CsF quaternary molten fluoride salt system can also form ion transport channels after high-temperature activation, and together with the fluoride ion solid electrolyte, it constitutes a solid-liquid dual electrolyte structure. Example 18 Same as Example 1, except that: (1) The negative electrode material is metallic La, and the other methods are the same.

[0059] The results show that using metallic La as the negative electrode results in a lower discharge specific capacity.

[0060] Example 19 Same as Example 1, except that: (1) The negative electrode material is metallic Ca, and the other methods are the same.

[0061] The results show that using metallic Ca as the negative electrode results in a lower discharge specific capacity.

[0062] Example 20 Same as Example 1, except that: (1) The negative electrode material is metallic Mg, and the other methods are the same.

[0063] The results show that using metallic Mg as the negative electrode results in a lower discharge specific capacity.

[0064] Example 21 Same as Example 1, except that: (1) The test temperature is 550℃, and the other methods are the same.

[0065] The results show that the operating voltage of a single cell increases with increasing test temperature.

[0066] Example 22 Same as Example 1, except that: (1) The test temperature is 600℃, and the other methods are the same.

[0067] The results show that the operating voltage of a single cell increases with increasing test temperature.

Claims

1. A high-voltage fluorine-ion thermal battery with a dual-electrolyte structure, characterized in that, The fluorine-ion thermal battery comprises a composite positive electrode layer, a fluorine-ion solid electrolyte layer, a molten fluoride salt electrolyte layer, and a negative electrode layer arranged sequentially.

2. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 1, characterized in that, The composite positive electrode layer, the fluoride ion solid electrolyte layer, and the molten fluoride salt electrolyte layer are all formed by pressing solid powder, and the negative electrode layer is composed of one of the following: metal sheet, metal powder, or metal alloy sheet.

3. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 1, characterized in that, The composite positive electrode layer comprises a transition metal fluoride, a fluoride ion solid electrolyte, and a conductive carbon material; the mass ratio of each component is: transition metal fluoride : fluoride ion solid electrolyte : conductive carbon material = (20-80) : (10-70) : (1-20).

4. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 3, characterized in that, The transition metal fluoride is one or more of CuF2, NiF2, FeF3, BiF3, CoF2, and MnF3; the conductive carbon material is one or more of carbon nanotubes, acetylene black, conductive graphite, and graphene; and the fluoride ion solid electrolyte is one or more of LaF3-based, alkaline earth metal fluoride-based, PbF2-based, SnF2-based, or composite fluoride solid electrolytes.

5. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 1, characterized in that, The fluoride ion solid electrolyte layer is disposed between the composite positive electrode layer and the molten fluoride salt electrolyte layer; the fluoride ion solid electrolyte is one or more of LaF3-based, alkaline earth metal fluoride-based, PbF2-based, SnF2-based, or composite fluoride solid electrolytes.

6. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 1, characterized in that, The molten fluoride electrolyte layer comprises molten fluoride and a ceramic proppant; the mass fraction of the ceramic proppant in the molten fluoride electrolyte layer is 10 wt.% to 70 wt.%; the molten fluoride is one or more of LiF, NaF, KF, and CsF; and the ceramic proppant is one or more of MgO, Al2O3, ZrO2, and SiO2.

7. The high-voltage fluorine-ion thermal battery with a dual-electrolyte structure according to claim 1, characterized in that, The negative electrode layer is an active metal or alloy that can undergo an electrochemical reaction with fluoride ions; the negative electrode material of the negative electrode layer is one of Li-B alloy, metal La, metal Mg, and metal Ca.

8. A method for preparing a high-voltage fluorine-ion thermal battery with a dual-electrolyte structure as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1, constructing a layered battery structure: In the compression mold, add nickel foam, composite positive electrode powder, fluoride ion solid electrolyte, molten fluoride salt electrolyte powder and negative electrode material in sequence to form a layered structure in which the composite positive electrode layer, fluoride ion solid electrolyte layer, molten fluoride salt electrolyte layer and negative electrode layer are stacked in sequence. Step 2, pressing and molding: The above-mentioned layered structure powder is pressed to obtain a fluorine-ion thermal battery cell with a dual electrolyte structure; Step 3, High-temperature activation discharge: The fluorine-ion thermal battery cell with dual electrolyte structure is heated to the working temperature of the molten fluorine salt electrolyte layer, so that the molten fluorine salt electrolyte melts and forms an ion transport channel, and then a constant current discharge test is performed.

9. The preparation method according to claim 8, characterized in that, In step 1, the mass of the fluoride ion solid electrolyte powder in the fluoride ion solid electrolyte layer is 10 wt.% to 50 wt.% of the mass of the composite positive electrode layer.

10. The preparation method according to claim 10, characterized in that, In step 2, the pressing process includes: first holding the pressure at 1t to 5t for 0.5 min to 5 min, and then holding the pressure at 15t to 20t for 5 min to 20 min; in step 3, the temperature of the high-temperature activation discharge is 500℃ to 600℃.

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