Preparation method of high-performance solid electrolyte membrane Joule hot pressed sintering

Abstract

The invention relates to the technical field of membrane separation, and discloses a preparation method of a high-performance solid electrolyte membrane Joule hot pressed sintering. According to the method, a Joule hot pressing sintering process is adopted, solid electrolyte powder is taken as a raw material, a proper amount of powder is weighed and put into a mold of Joule hot pressing equipment, and pressure is applied to an upper graphite plate and a lower graphite plate in a vacuum or inert gas environment. Through the synergistic effect of external pressure and Joule heat, the temperature of the material can be rapidly increased to 800-1500 DEG C in an extremely short time, and heat-preservation sintering is completed, so that the sintering period is remarkably shortened, the preparation efficiency is improved, and a compact and high-performance solid electrolyte membrane is obtained. Compared with a traditional heating furnace which needs at least more than 3 hours in heating time and Joule hot pressing is controlled within 1 minute, the heating time can be effectively shortened by at least 90% or more, and the prepared solid electrolyte membrane has high density and low defects, shows excellent ion separation performance and is suitable for industrial production. And a reference thought is provided for related fields such as efficient recovery and extraction of lithium resources.

Description

A method for preparing high-performance solid electrolyte membranes by Joule hot pressing sintering Technical Field

[0001] This invention belongs to the field of membrane separation technology, and in particular relates to a method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering. Background Technology

[0002] With the continuous growth of global energy demand and increasing focus on environmental sustainability, the search for efficient and clean energy solutions has become increasingly important. Lithium-ion batteries play a key role in energy storage and conversion technologies, and the global demand for lithium continues to grow.

[0003] Lithium salts are primarily extracted from mineral sediments and salt lakes. Current methods for extracting lithium and its compounds involve acid decomposition and chemical leaching of minerals or concentration using brine from solar ponds. However, these traditional methods are complex, time-consuming, or highly dependent on chemicals or local climate. Membrane separation technology offers several important advantages, including high selectivity, greater environmental sustainability, ease of operation, and strong scalability, making it an excellent choice for lithium ion extraction.

[0004] To effectively address the above problems, this invention utilizes a solid electrolyte membrane to replace traditional lithium extraction methods, which is more time-saving and cleaner. Solid electrolyte materials possess high ionic conductivity, effectively promoting lithium-ion transport. In contrast, other materials may suffer from concentration polarization and ion migration, affecting lithium-ion transport efficiency. Furthermore, solid electrolyte materials exhibit good chemical stability, effectively resisting environmental influences such as corrosion and oxidation from seawater. Therefore, combining solid electrolytes with membrane separation technology to prepare highly selective solid electrolyte membranes is crucial.

[0005] To obtain solid-state electrolyte ceramic membranes with high ionic conductivity and strong mechanical properties, extremely high sintering temperatures (often exceeding 1000°C, or even 1200°C) are typically required. While traditional sintering processes involve prolonged high-temperature treatment, which promotes particle bonding, they inevitably lead to the significant volatilization of critical lithium. This lithium loss not only generates non-conductive impurity phases but also hinders the complete densification of the ceramic membrane, leaving numerous pores and microcracks on the material surface and at grain boundaries. These chemical and structural defects severely impair the ion flux and selectivity of the material, resulting in decreased separation performance and reduced membrane lifetime. Therefore, this invention utilizes a hot-press Joule apparatus to obtain a high-flux, highly selective, dense solid-state electrolyte membrane through synergistic rapid heating and the application of mechanical pressure.

[0006] Currently, there is an urgent need in this field to develop a solid electrolyte membrane with high lithium-ion selectivity and long lifespan for lithium-ion extraction. Summary of the Invention

[0007] The object of the present invention is to overcome the difficulties in lithium extraction in the prior art, prepare a lithium superionic conductor separation membrane with high selectivity, and obtain a solid electrolyte ceramic membrane with high density, high ionic conductivity and strong mechanical properties.

[0008] The technical solution of the present invention is as follows: A preparation method for joule hot pressing and sintering of a high-performance solid electrolyte membrane, and the specific operation steps are as follows: A: Calculate the mass of the solid electrolyte powder required for hot pressing and sintering a material with a specific thickness according to the size of the mold. After weighing the required solid electrolyte powder, put it into a graphite mold, and apply pressure to the upper and lower graphite plates so that the powder and the graphite mold are in full contact; B: Place both the solid electrolyte powder and the graphite mold in a vacuum or inert gas environment for pressurization. After the pressure reaches the set pressure, maintain the set pressure, and perform joule heat-up. Stop heating when the temperature rises to 800-1500°C, and keep warm for 0.5-60 minutes. After cooling to room temperature, relieve the pressure to obtain a solid electrolyte membrane.

[0009] Further, in the above preparation method for joule hot pressing and sintering of a high-performance solid electrolyte membrane, in step A, the solid electrolyte powder is Li 1+x Al x Ti 2–x (PO4)3 (0 < x < 2, LATP), Li 3x La 2 / 3-x TiO3 (LLTO, 0 < x < 0.16), Li7La3Zr2O 12 (LLZO), Li 1+x Al x Ge 2–x (PO4)3 (0 < x < 2, LAGP), Li 7-x La3Zr 2-x Ta x O 12 (0 < x < 2, LLZTO), Li 7-x La3Zr 2-x Al x O 12 (0 < x < 2, LLZAO), LiMn2O4 (LMO) or LiFePO4 (LFP).

[0010] Further, in the above preparation method for joule hot pressing and sintering of a high-performance solid electrolyte membrane, in step A, the thickness of the sintered material for hot pressing is 0.5-3 mm.

[0011] Further, in the above preparation method for joule hot pressing and sintering of a high-performance solid electrolyte membrane, in step B, the pressure in joule hot pressing increases at a rate of 1-5 MPa / s, and the set pressure is 0-100 MPa.

[0012] Furthermore, in the above-mentioned method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering, the heating rate of Joule hot pressing in step B is 10-50 ℃ / s.

[0013] Beneficial Effects: Compared with existing technologies, the solid electrolyte ceramic membrane prepared by this invention possesses advantages such as high density, high mechanical strength, and high lithium-ion flux. Through rapid sintering under ultra-high pressure, the membrane density is increased from 85% to over 99% using traditional sintering methods, and the hardness is increased by 40% to 60%. Traditional sintering often leads to low density and lithium loss in solid electrolyte ceramic membranes. However, this invention, through rapid sintering under ultra-high pressure (heating rate of 10–50 °C / s), significantly shortens the lithium volatilization window, effectively suppressing mass loss and increasing lithium-ion flux by approximately 70% compared to traditional methods. Furthermore, applying pressure during sintering significantly reduces the atomic diffusion barrier, lowering the membrane densification temperature to 60%–75% of the temperature required by traditional sintering methods. This allows for the preparation of high-density solid electrolyte ceramic membranes at lower temperatures and in a shorter time, surpassing traditional methods. Attached Figure Description

[0014] Figure 1 is a SEM image of the solid electrolyte membranes prepared in Examples 1, 2, 3 and 4.

[0015] Figure 2 is a schematic diagram of the water contact angle of the solid electrolyte membranes prepared in Examples 1, 2, 3 and 4.

[0016] Figure 3 is a schematic diagram of the electrodialysis membrane module device shown in Example 7.

[0017] Figure 4 shows the lithium-ion extraction performance of the solid electrolyte membrane used for electrodialysis in Example 7.

[0018] Figure 5 is a SEM image of the solid electrolyte membranes prepared in Comparative Example 1, Example 2, and Example 3.

[0019] Figure 6 is a schematic diagram of the water contact angle of the solid electrolyte membranes prepared in Comparative Example 1, Example 2 and Example 3. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. The relative density is determined according to Archimedes' displacement method, and the hardness is measured using a Vickers hardness tester. Example 1

[0021] This embodiment illustrates the preparation of LLZTO membranes via hot pressing Joule sintering.

[0022] First, the LLZTO material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0023] The mass of LLZTO powder required for hot pressing a sintered material with a thickness of 500 µm was calculated based on the mold size. After weighing the required amount, the uniformly mixed powder was directly loaded into the Joule hot press mold. The pressure was increased to 50 MPa at a rate of 1 MPa / s. After the pressure reached the set value, the temperature was raised to 1200 ℃ at a rate of 20 ℃ / s and held for 30 min. Finally, the temperature was allowed to cool naturally to room temperature to obtain an LLZTO film with a relative density of 99.8% and a hardness of 6.7 GPa.

[0024] Figure 1a is a cross-sectional SEM image of the LLZTO membrane prepared in this embodiment, and Figure 1e is an enlarged view. The membrane exhibits a completely dense structure with a smooth fracture surface and no obvious pores. The original small particles have melted and recrystallized to form large continuous crystal faces. Figure 2a is a schematic diagram of the water contact angle of the LLZTO membrane prepared in this embodiment. Example 2

[0025] This embodiment illustrates the preparation of LLTO membranes via hot pressing Joule sintering.

[0026] First, the LLTO material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0027] The mass of LLTO powder required for hot pressing a 2 mm thick sintered material was calculated based on the mold size. After weighing the required amount, the uniformly mixed powder was directly loaded into the Joule hot press mold. The pressure was increased to 20 MPa at a rate of 1 MPa / s. After the pressure reached the set value, the temperature was raised to 1300 ℃ at a rate of 10 ℃ / s and held for 0.5 min. Finally, the temperature was allowed to cool naturally to room temperature to obtain an LLTO film with a relative density of 99.6% and a hardness of 9.1 GPa.

[0028] Figure 1b is a cross-sectional SEM image of the LLTO membrane prepared in this embodiment, and Figure 1f is an enlarged view. The membrane exhibits a dense structure, with small particles having melted and recrystallized, but some even smaller spherical particles are attached to the surface, indicating that the sintering or heat treatment of the material was insufficient. Figure 2b is a schematic diagram of the water contact angle of the LLTO membrane prepared in this embodiment. Example 3

[0029] This embodiment illustrates the preparation of LATP membranes via hot-pressing Joule sintering.

[0030] First, the LATP material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0031] The mass of LATP powder required for hot pressing a sintered material with a thickness of 500 µm was calculated based on the mold size. After weighing the required amount, the uniformly mixed powder was directly loaded into the Joule hot press mold. The pressure was increased to 30 MPa at a rate of 1 MPa / s. After the pressure reached the set value, the temperature was raised to 800 ℃ at a rate of 50 ℃ / s and held for 10 min. Finally, the temperature was allowed to cool naturally to room temperature to obtain an LATP film with a relative density of 96.5% and a hardness of 8.3 GPa.

[0032] Figure 1c is a cross-sectional SEM image of the LATP membrane prepared in this embodiment, and Figure 1g is an enlarged view. The membrane powder particles begin to melt, but do not form continuous crystal planes. The top of the membrane has a denser skin layer, but the structure below it is loose. Figure 2c is a schematic diagram of the water contact angle of the LATP membrane prepared in this embodiment. Example 4

[0033] This embodiment illustrates the preparation of LMO membranes via hot pressing Joule sintering.

[0034] First, the LMO material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0035] The mass of LMO powder required for hot pressing a 1 mm thick sintered material was calculated based on the mold size. After weighing the required amount, the uniformly mixed powder was directly loaded into the Joule hot press mold. The pressure was increased to 100 MPa at a rate of 5 MPa / s. After the pressure reached the set value, the temperature was raised to 900 ℃ at a rate of 10 ℃ / s and held for 60 min. Finally, the temperature was allowed to cool naturally to room temperature to obtain an LMO film with a relative density of 99.4% and a hardness of 10.3 GPa.

[0036] Figure 1d is a cross-sectional SEM image of the LMO membrane prepared in this embodiment. Figure 1h is a magnified view, showing that the membrane has achieved densification and small grains are swallowed by large grains, resulting in significant grain growth. Figure 2d is a schematic diagram of the water contact angle of the LMO membrane prepared in this embodiment. Example 5

[0037] This embodiment illustrates the preparation of LLZO films via hot pressing Joule sintering.

[0038] First, the LLZO material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0039] The mass of LLZO powder required for hot pressing a 1 mm thick sintered material was calculated based on the mold size. The required amount was weighed and the uniformly mixed powder was directly loaded into a Joule hot press mold. The pressure was increased to 5 MPa at a rate of 1 MPa / s. After reaching the set pressure, the temperature was raised to 1000 °C at a rate of 10 °C / s and held for 5 min. Finally, the temperature was allowed to cool naturally to room temperature, yielding an LLZO film with a relative density of 96.4% and a hardness of 8.9 GPa. Example 6

[0040] This embodiment illustrates the preparation of LATP membranes via hot-pressing Joule sintering.

[0041] First, the LATP material was ball-milled for 3 hours at a speed of 400 rpm to ensure the uniformity of the material particle size.

[0042] The mass of LATP powder required for hot-pressing a 3 mm thick sintered material was calculated based on the mold size. The required amount was weighed and the uniformly mixed powder was directly loaded into a Joule hot-press mold. Pressing was performed at 0 MPa. After the pressure reached the set value, the temperature was increased to 1500 °C at a rate of 10 °C / s and held for 20 min. Finally, it was allowed to cool naturally to room temperature to obtain an LATP film with a relative density of 87.4% and a hardness of 7.8 GPa. Example 7

[0043] This embodiment illustrates the performance of solid electrolyte membranes for lithium-ion extraction using electrodialysis testing.

[0044] Electrodialysis tests were conducted using the LLZTO membrane prepared by conventional sintering in Comparative Example 1 and the LLZTO membrane prepared by hot pressing sintering in Example 1.

[0045] Three solutions—lithium enrichment solution, feed solution, and electrode solution—were successively introduced into the electrodialysis apparatus. The feed solution was a mixed solution of 0.1 mol / L LiCl, 0.1 mol / L NaCl, and 0.1 mol / L MgCl₂; the lithium enrichment solution was a pure aqueous solution; and the electrode solution was a 0.1 mol / L KCl solution. The voltage applied to the electrodialysis apparatus was 1.2 V, and the effective membrane area during testing was 5 × 10⁻⁶. -5 m 2 All experiments were conducted at room temperature.

[0046] As lithium gradually concentrates in the lithium-enriched solution over time, after 48 hours of electrodialysis testing, the lithium-ion flux of the conventionally sintered LLZTO membrane and the hot-pressed LLZTO membrane were found to be 0.573 mol•m. -2 •h -1 1.01 mol•m -2 •h -1The selectivity for lithium and sodium was 8.55 and 35.1, respectively. The selectivity for lithium and magnesium was 17.8 and 990.8, respectively.

[0047] Figure 3 is a schematic diagram of the electrodialysis membrane module device used in this embodiment. Figure 4 is a graph of lithium ion extraction performance obtained after electrodialysis testing in this embodiment.

[0048] Comparative Example 1 This example illustrates the preparation of LLZTO membranes using a conventional sintering method.

[0049] First, the LLZTO material was ball-milled for 3 hours at 400 rpm to ensure uniform particle size. The mass of LLZTO powder required for a 500 µm thick sintering material was calculated based on the mold size. The uniformly mixed powder was loaded into a pressing mold and pressurized to 50 MPa for 30 seconds to obtain a green body. The green body was then placed in a muffle furnace and heated to 1300 °C at a rate of 1 °C / min, holding for 20 hours to obtain the final LLZTO film with a relative density of 87.3% and a hardness of 5.3 GPa.

[0050] Figure 5a is a cross-sectional SEM image of the LLZTO membrane prepared in this embodiment. Figure 5e is an enlarged view showing that the material is in a molten state. Although there are clear grain boundaries between the grains, they are tightly bonded with few pores, resulting in a relatively dense overall structure. Figure 6a is a schematic diagram of the water contact angle of the LLZTO membrane prepared in this embodiment.

[0051] Comparative Example 2 This example illustrates the preparation of LATP membranes using a conventional sintering method.

[0052] First, the LATP material was ball-milled for 3 hours at 400 rpm to ensure uniform particle size. The mass of LATP powder required for a 500 µm thick sintered material was calculated based on the mold size. The uniformly mixed powder was loaded into a compression mold and pressurized to 30 MPa for 30 seconds to obtain a green body. The green body was then placed in a muffle furnace and heated to 1100 °C at a rate of 2 °C / min, holding for 12 hours to obtain the final LATP film with a relative density of 78.6% and a hardness of 6.2 GPa.

[0053] Figure 5b is a cross-sectional SEM image of the LATP membrane prepared in this embodiment, and Figure 5f is an enlarged view, showing that the material is in a molten state, but there are a large number of tiny pores between the particles, and the membrane is not dense. Figure 6b is a schematic diagram of the water contact angle of the LATP membrane prepared in this embodiment.

[0054] Comparative Example 3 This example is used to illustrate the preparation of LMO membranes by conventional sintering methods.

[0055] First, the LMO material was ball-milled for 3 hours at 400 rpm to ensure uniform particle size. The mass of LMO powder required for a 1 mm thick sintering material was calculated based on the mold size. The uniformly mixed powder was then loaded into a pressing mold and pressurized to 50 MPa for 30 seconds to obtain a green body. The green body was then placed in a muffle furnace and heated to 1100 °C at a rate of 5 °C / min, holding for 12 hours to obtain an LMO film with a relative density of 87.1% and a hardness of 8.6 GPa.

[0056] Figure 5c is a cross-sectional SEM image of the LMO membrane prepared in this embodiment, and Figure 5g is an enlarged view, showing that the material is in a molten state, but the particles are connected by necks, exhibiting high porosity. Figure 6c is a schematic diagram of the water contact angle of the LMO membrane prepared in this embodiment.

Claims

1. A method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering, characterized in that, Includes the following steps: A: Calculate the mass of solid electrolyte powder required for hot-pressing a sintered material of a specific thickness based on the mold size. Weigh the required solid electrolyte powder and place it in the graphite mold. Apply pressure to the upper and lower graphite plates to ensure sufficient contact between the powder and the graphite mold. B: Place both the solid electrolyte powder and the graphite mold in a vacuum or inert gas environment and pressurize them. After the pressure reaches the set pressure, maintain the set pressure and perform Joule heating. Stop heating when the temperature reaches 800-1500℃ and hold for 0.5-60 minutes. Release the pressure after cooling to room temperature to obtain the solid electrolyte membrane.

2. The method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering according to claim 1, characterized in that: In step A, the solid electrolyte powder is Li 1+x Al x Ti 2–x (PO4)3 (0 < x < 2, LATP), Li 3x La 2 / 3-x TiO3 (LLTO, 0 < x < 0.16), Li7La3Zr2O 12 (LLZO), Li 1+x Al x Ge 2–x (PO4)3 (0 < x < 2, LAGP), Li 7-x La3Zr 2-x Ta x O 12 (0 < x < 2, LLZTO), Li 7-x La3Zr 2-x Al x O 12 (0 < x < 2, LLZAO), LiMn2O4 (LMO) or LiFePO4 (LFP).

3. The method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering according to claim 1, characterized in that: In step A, the specific thickness of the hot-pressed sintered material is 0.5 to 3 mm.

4. The method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering according to claim 1, characterized in that: In step B, the pressure is increased at a rate of 1 to 5 MPa / s, and the pressure is set to 0 to 100 MPa.

5. The method for preparing a high-performance solid electrolyte membrane by Joule hot pressing sintering according to claim 1, characterized in that: In step B, the heating rate of the Joule heating is 10–50 °C / s.

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