Solid-state lithium-ion conductors, their preparation methods, and their applications in thermal battery electrolytes

Abstract

This invention provides a solid-state lithium-ion conductor, its preparation method, and its application in thermal battery electrolytes. This fast-ion conductor type thermal battery electrolyte material comprises two main components: a Li-β”-Al2O3 solid-state lithium-ion conductor and multi-element alkali metal eutectic salts such as LiF-LiCl-LiBr, LiCl-KCl, and LiCl-LiBr-KBr. The specific preparation method involves: Li2CO3, γ-Al2O3, and Na2CO3 raw materials are calcined at high temperature in a specific ratio to obtain the Li-β”-Al2O3 solid-state lithium-ion conductor; LiF, LiCl, LiBr, and KBr raw materials are calcined at high temperature in a specific ratio to obtain the multi-element alkali metal eutectic salt; and the solid conductor and multi-element eutectic salt are then uniformly mixed and reacted at a constant temperature to obtain the fast-ion conductor type thermal battery electrolyte material. The fast-ion conductor type electrolyte prepared by this invention effectively improves the ionic conductivity of the "electrolyte / separator integrated layer" of the thermal battery, significantly reduces the battery's internal resistance, and enhances the high-power, high-current output characteristics of the thermal battery.

Description

Technical Field

[0001] This invention belongs to the field of thermal battery technology, and particularly relates to a solid lithium-ion conductor, its preparation method, and its application in thermal battery electrolytes. Background Technology

[0002] A thermal battery is a type of primary power supply backup battery. It has no power output in the room temperature storage state, but it is activated at high temperature and can reliably supply power in various extreme temperature environments from -55℃ to +600℃. It is an important supporting power source for modern high-speed strike weapons, such as medium and long-range missiles, guided aerial bombs, miniature smart munitions, and anti-ship / anti-submarine torpedoes, and occupies an important position in the military field.

[0003] A thermal battery mainly consists of five components: a positive electrode, a negative electrode, an electrolyte, an activation and heating system, and a heat preservation system. The biggest difference between the electrolyte in a thermal battery and those used in other lithium-ion batteries, lithium metal batteries, and solid-state batteries lies in its composition and ionic conductivity. Ordinary thermal battery electrolytes are mostly composed of a porous adsorbent carrier and an alkali metal eutectic salt. The porous binder acts as an insulator, and the alkali metal eutectic salt melts into a liquid state at high temperatures, dissociating Li... + Under the influence of an electric field, they move directionally, thus transferring charge. At the common operating temperature of 400℃~500℃ in thermal batteries, alkali metal eutectic salts exhibit extremely high ionic conductivity, reaching 1.0 S / cm. 2 The above figures are more than 10 times higher than those used in other lithium-ion batteries, lithium metal batteries, and solid-state batteries. However, the porous adsorbent carriers used in ordinary thermal batteries are mostly composed of MgO insulators, which seriously affects the overall ionic conductivity level of the thermal battery electrolyte, thus limiting further improvement in the power characteristics of thermal batteries.

[0004] Li-β”-Al2O3 is a solid lithium-ion conductor that has been extensively studied in the field of lithium-ion secondary batteries, and is commonly used for coating positive and negative electrode surfaces and modifying solid electrolytes. Li-β”-Al2O3 powder exhibits excellent thermal and chemical stability. By controlling the synthesis parameters, porous Li-β”-Al2O3 suitable for the working characteristics of thermal battery electrolytes can be prepared. Combined with alkali metal eutectic salts, it forms a fully conductive fast-ion conductor thermal battery electrolyte, theoretically further improving the overall ionic conductivity of the thermal battery electrolyte, thereby enhancing the power output characteristics of the thermal battery. Therefore, the development of fast-ion conductor thermal battery electrolyte materials is of significant research importance. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a solid lithium-ion conductor, its preparation method, and its application in thermal battery electrolytes. This material solves the problem of insulating porous adsorption carriers limiting electrolyte ion conductivity and thermal battery high power output.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a solid lithium-ion conductor, wherein Li2CO3, γ-Al2O3 and Na2CO3 are mixed in a molar ratio of 1:2:0.2 to 1:5:1 to obtain reaction raw materials; after the reaction raw materials are mixed evenly, a constant temperature reaction is carried out, and after the reaction is completed, the temperature is lowered to room temperature to obtain a reaction product; the reaction product is crushed and sieved to obtain a Li-β”-Al2O3 solid lithium-ion conductor.

[0007] Furthermore, the reaction raw materials are mixed evenly using a high-speed ball milling method, with a ball milling speed of 200 rpm to 500 rpm and a ball milling time of 3 h to 6 h.

[0008] Furthermore, the isothermal reaction is carried out in a magnesium oxide crucible, an aluminum oxide crucible, or a quartz crucible, with the crucible volume being 5 to 10 times that of the reaction raw materials.

[0009] Furthermore, the temperature of the isothermal reaction is 1000℃~1700℃, and the reaction time is 2h~6h; the heating atmosphere of the isothermal reaction is air, nitrogen or argon; and the sieve used for sieving has a mesh size of 80 mesh~300 mesh.

[0010] Solid-state lithium-ion conductors prepared by the above method.

[0011] A method for preparing an electrolyte material for a fast-ion conductor type thermal battery includes the following steps: The solid lithium-ion conductor prepared above is mixed with a multi-element alkali metal eutectic salt in a mass ratio of 4:1 to 1:1 to obtain an electrolyte raw material. After the electrolyte raw materials are mixed evenly, a constant temperature reaction is carried out. After the reaction is completed, the temperature is lowered to room temperature to obtain the reaction product. The reaction products are crushed and sieved to obtain the electrolyte material for the thermal battery.

[0012] Furthermore, the multi-alkali metal eutectic salt is one of the following systems: LiCl-KCl, LiF-LiBr-KBr, LiCl-LiBr-KBr, LiF-LiCl-LiBr, LiF-NaF-KF, and LiCl-KCl-LiF molten salt system.

[0013] Furthermore, the electrolyte raw material is placed in a crucible and subjected to a constant-temperature reaction at a temperature of 300℃ to 600℃ for a reaction time of 2h to 6h, with the heating atmosphere being one of air, nitrogen, or argon.

[0014] Furthermore, in the crushing and screening step, the screen used for screening has a mesh size of 40 to 300.

[0015] Electrolyte material for fast ion conductor type thermal batteries prepared by the above method.

[0016] The advantages and positive effects of this invention are: (1) By adjusting the ratio of raw materials and the high temperature of high-temperature synthesis reaction, this invention can screen and prepare Li-β”-Al2O3 with high thermal stability and chemical stability.

[0017] (2) The present invention can prepare Li-β”-Al2O3 solid lithium-ion conductor with good dispersibility and porous morphology. It can be used as a porous carrier to adsorb liquid alkali metal eutectic salt and has fast ion conductor properties, which can improve the overall conductivity level of the electrolyte of the thermal battery when working at high temperature.

[0018] (3) The present invention uses conventional reactants as initial reaction raw materials and uses high-temperature solid-state sintering to prepare Li-β”-Al2O3 fast ion conductor, which makes the raw material preparation and reaction equipment relatively simple, reduces the preparation cost, and can be mass-produced, making it particularly suitable for industrial applications. Attached Figure Description

[0019] Figure 1 The XRD pattern of the solid lithium-ion conductor prepared in Example 1 of the present invention (where a is the XRD curve and b is the SEM image).

[0020] Figure 2 The microstructure characterization and conductivity test diagrams of the solid lithium-ion conductor prepared in Example 2 of the present invention are shown (where a is the microstructure and b is the electrochemical impedance spectroscopy).

[0021] Figure 3 The discharge curve of the fast ion conductor type thermal battery electrolyte prepared in Example 3 of the present invention.

[0022] Figure 4 The discharge curve of the fast ion conductor type thermal battery electrolyte prepared in Example 4 of the present invention.

[0023] Figure 5 The discharge curves are for electrolytes in conventional thermal batteries. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1 S1: Ingredients: Mix Li2CO3, γ-Al2O3 and Na2CO3 in a molar ratio of 1:5:0.2 to prepare the reaction raw materials.

[0026] S2: Raw material mixing: Place the reaction raw materials into a high-speed ball mill, set the speed to 400 rpm, and run for 6 hours.

[0027] S3: Isothermal reaction: Transfer the ball-milled reaction material to a 300 mL magnesium oxide crucible, and then place the crucible in an isothermal device. Set the reaction temperature to 1600℃, the heating rate to 5℃ / min, and the isothermal time to 2 hours. The heating environment is an air atmosphere.

[0028] S4: Cooling: After the isothermal reaction is complete, set the cooling rate to 5℃ / min, and remove the sample after it has cooled to room temperature. S5: Crushing: The reaction product is crushed and sieved through a 120-mesh sieve to obtain a white powder sample, which is Li-β”-Al2O3.

[0029] The XRD crystal structure of the Li-β”-Al2O3 prepared in this embodiment was determined. The results showed that the XRD pattern of the prepared sample was consistent with that of the Li-β”-Al2O3 standard, proving that Li-β”-Al2O3 with high crystallinity can be synthesized under this temperature condition. The test results are as follows. Figure 1 The XRD curve is shown in (a). Additionally... Figure 1 (b) SEM images show that the prepared Li-β”-Al2O3 has an irregular blocky morphology, and its particle size is distributed between 5-8 μm.

[0030] Example 2 S1: Ingredients: Mix Li2CO3, γ-Al2O3 and Na2CO3 in a molar ratio of 1:5:0.2 to prepare the reaction raw materials.

[0031] S2: Raw material mixing: Place the reaction raw materials into a high-speed ball mill, set the speed to 400 rpm, and run for 6 hours.

[0032] S3: Isothermal reaction: Transfer the ball-milled reaction material to a 300 mL magnesium oxide crucible, and then place the crucible in an isothermal device. Set the reaction temperature to 1250℃, the heating rate to 5℃ / min, and the isothermal time to 2 hours. The heating environment is an air atmosphere.

[0033] S4: Cooling: After the isothermal reaction is complete, set the cooling rate to 5℃ / min, and remove the sample after it has cooled to room temperature. S5: Crushing: The reaction product is crushed and sieved through a 120-mesh sieve to obtain a white powder sample, which is Li-β”-Al2O3.

[0034] The Li-β”-Al2O3 prepared in this embodiment was characterized by its microstructure and conductivity. The results showed that the prepared Li-β”-Al2O3 had an irregular blocky morphology, with a particle size distribution between 2-3 μm. The calculated conductivity was 2.17 × 10⁻⁶. -3 S / cm. Test results are as follows: Figure 2 (b) shows the electrochemical impedance spectroscopy. Figure 2 (a) shows the microstructure of the prepared sample.

[0035] Example 3 A method for preparing a fast-ion conductor type thermal battery electrolyte material includes: S1: Ingredients: The Li-β”-Al2O3 solid lithium-ion conductor prepared in Example 2 and the LiCl-LiBr-KBr eutectic salt are prepared into electrolyte raw materials in a mass ratio of 3:1.

[0036] S2: Raw material mixing: Place the electrolyte raw material in a 500ml magnesium oxide crucible and mix thoroughly.

[0037] S3: Isothermal reaction: The uniformly mixed electrolyte raw materials are placed in an isothermal device and the reaction is carried out at 500°C in a nitrogen atmosphere.

[0038] S4: Cooling: After the isothermal reaction is completed, the electrolyte raw material is quickly removed from the isothermal device until the reaction product is cooled to room temperature.

[0039] S4: Crushing: The reaction product is crushed and sieved through a 60-mesh sieve to obtain a white powder sample, which is the fast ion conductor electrolyte material.

[0040] The prepared electrolyte material and the FeCoS2 positive electrode for thermal batteries were pressed into sheets, and then assembled into thermal battery cells in the order of negative electrode LiB sheet, electrolyte sheet, and FeCoS2 positive electrode sheet. Fifteen cells were then assembled into a unit cell. The unit cell was then tested at 500℃ with a current of 0.1 A / cm². 2 A constant current discharge is performed using a specific current density, during which 1.5 A / cm² is output every 150 seconds. 2 The pulse current, the test results are as follows Figure 3 The discharge curve of a fast ion conductor type thermal battery electrolyte shows that when the lower operating voltage is 24V, the operating time is 1531 s.

[0041] Example 4 A method for preparing a fast-ion conductor type thermal battery electrolyte material includes: S1: Ingredients: The Li-β”-Al2O3 solid lithium-ion conductor prepared in Example 2 and the LiF-LiCl-LiBr eutectic salt are prepared in a mass ratio of 1:1 to form electrolyte raw materials.

[0042] S2: Raw material mixing: Place the electrolyte raw material in a 500ml magnesium oxide crucible and mix thoroughly.

[0043] S3: Isothermal reaction: The uniformly mixed electrolyte raw materials are placed in an isothermal device and the reaction is carried out at 500°C in a nitrogen atmosphere.

[0044] S4: Cooling: After the isothermal reaction is completed, the electrolyte raw material is quickly removed from the isothermal device until the reaction product is cooled to room temperature.

[0045] S4: Crushing: The reaction product is crushed and sieved through a 60-mesh sieve to obtain a white powder sample, which is the fast ion conductor electrolyte material.

[0046] The prepared electrolyte material and the FeCoS2 positive electrode for thermal batteries were pressed into sheets, and then assembled into thermal battery cells in the order of negative electrode LiB sheet, electrolyte sheet, and FeCoS2 positive electrode sheet. Fifteen cells were then assembled into a unit cell. The unit cell was then tested at 500℃ with a current of 0.3 A / cm². 2 A constant current discharge is performed using a specific current density, during which 3.5 A / cm² is output every 40 seconds. 2 The pulse current, the test results are as follows Figure 4 The discharge curve of a fast ion conductor type thermal battery electrolyte shows that when the lower operating voltage is 24V, the operating time is 480 s.

[0047] Comparative Example 1 A method for preparing a thermal battery electrolyte material using conventional MgO as a binder includes: S1: Ingredients: Prepare electrolyte raw materials by mixing conventional MgO binder and LiF-LiCl-LiBr eutectic salt in a mass ratio of 1:1.

[0048] S2: Raw material mixing: Place the electrolyte raw material in a 500mL corundum crucible and mix thoroughly.

[0049] S3: Isothermal reaction: Place the uniformly mixed electrolyte raw materials in an isothermal device and carry out the isothermal reaction at 500℃.

[0050] S4: Cooling: After the isothermal reaction is complete, quickly remove the reaction product from the isothermal device until it cools to room temperature.

[0051] S5: Crushing: The reaction product is crushed and sieved through a 60-mesh sieve to obtain a white powder sample, which is the electrolyte material for thermal batteries.

[0052] The prepared electrolyte material and the FeCoS2 positive electrode for thermal batteries were pressed into sheets, and then assembled into thermal battery cells in the order of negative electrode LiB sheet, electrolyte sheet, and FeCoS2 positive electrode sheet. Fifteen cells were then assembled into a unit cell. The unit cell was then tested at 500℃ with a current of 0.3 A / cm². 2 A constant current discharge is performed using a specific current density, during which 3.5 A / cm² is output every 40 seconds. 2 The pulse current, the test results are as follows Figure 5 The discharge curve of a conventional thermal battery electrolyte shows that the operating time is 430 s when the lower operating voltage is 24V.

[0053] In summary, the Li-β”-Al2O3 prepared at a reaction temperature of 1250℃ exhibits small-diameter micron-sized particles and a porous morphology, while also possessing high ionic conductivity. The electrolyte material prepared by combining it with multi-element alkali metal eutectic salts exhibits significant fast ion conductor characteristics, which is beneficial for reducing the polarization phenomenon during high-current operation of thermal batteries, thereby extending the discharge time of thermal batteries and reducing the voltage drop during pulse instantaneous events.

[0054] This invention uses conventional reactants, Li2CO3, γ-Al2O3, and Na2CO3, as initial reaction raw materials, and uses a high-temperature solid-state sintering method to prepare the reaction product Li-β”-Al2O3. Because the raw material preparation and reaction equipment are relatively simple, the preparation cost is reduced, and it can be mass-produced, making it particularly suitable for industrial applications.

[0055] Furthermore, the present invention provides a method for preparing electrolyte materials for thermal batteries by using Li-β”-Al2O3 as a fast ion conductor and adsorption support for the electrolyte, and combining it with one of the molten salt systems used in thermal batteries, such as LiCl-KCl, LiF-LiBr-KBr, LiCl-LiBr-KBr, LiF-LiCl-LiBr, LiF-NaF-KF, and LiCl-KCl-LiF, through high-temperature sintering. This method is a commonly used preparation method for electrolyte materials in thermal batteries.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a solid-state lithium-ion conductor, characterized in that, Li2CO3, γ-Al2O3 and Na2CO3 were mixed in a molar ratio of 1:2:0.2 to 1:5:1 to obtain the reaction raw materials; after the reaction raw materials were mixed evenly, they were subjected to a constant temperature reaction. After the reaction was completed, the mixture was cooled to room temperature to obtain the reaction product; the reaction product was crushed and sieved to obtain Li-β”-Al2O3 solid lithium-ion conductor.

2. The method for preparing a solid-state lithium-ion conductor according to claim 1, characterized in that, The reaction raw materials were mixed evenly using a high-speed ball milling method. The ball milling speed was 200 rpm to 500 rpm, and the ball milling time was 3 h to 6 h.

3. The method for preparing a solid-state lithium-ion conductor according to claim 1, characterized in that, The isothermal reaction is carried out in a magnesium oxide crucible, an aluminum oxide crucible, or a quartz crucible, with the crucible volume being 5 to 10 times the volume of the reaction raw materials.

4. The method for preparing a solid-state lithium-ion conductor according to claim 1, characterized in that, The isothermal reaction temperature is 1000℃~1700℃, and the reaction time is 2h~6h; the heating atmosphere for the isothermal reaction is air, nitrogen or argon; the sieve used for sieving has a mesh size of 80 mesh~300 mesh.

5. A solid lithium-ion conductor prepared by the method according to any one of claims 1-4.

6. A method for preparing an electrolyte material for a fast-ion conductor type thermal battery, characterized in that, Includes the following steps: The solid lithium-ion conductor prepared according to claim 5 is mixed with a multi-element alkali metal eutectic salt in a mass ratio of 4:1 to 1:1 to obtain an electrolyte raw material. After the electrolyte raw materials are mixed evenly, a constant temperature reaction is carried out. After the reaction is completed, the temperature is lowered to room temperature to obtain the reaction product. The reaction products are crushed and sieved to obtain the electrolyte material for the thermal battery.

7. The method for preparing the electrolyte material for a fast-ion conductor type thermal battery according to claim 6, characterized in that, The multi-alkali metal eutectic salt is one of the following systems: LiCl-KCl, LiF-LiBr-KBr, LiCl-LiBr-KBr, LiF-LiCl-LiBr, LiF-NaF-KF, and LiCl-KCl-LiF molten salt system.

8. The method for preparing the electrolyte material for a fast-ion conductor type thermal battery according to claim 6, characterized in that, The electrolyte raw material is placed in a crucible and subjected to a constant temperature reaction at a temperature of 300℃ to 600℃ for 2 hours to 6 hours. The heating atmosphere is one of air, nitrogen, or argon.

9. The method for preparing the electrolyte material for a fast-ion conductor type thermal battery according to claim 6, characterized in that, In the crushing and screening step, the screen used for screening has a mesh size of 40 to 300.

10. Electrolyte material for fast-ion conductor type thermal batteries prepared by the method according to any one of claims 6-9.

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