Preparation method of nanoscale titanium aluminum lithium phosphate solid electrolyte powder

Abstract

The application relates to a preparation method of a nanoscale lithium aluminum titanium phosphate solid electrolyte powder. First, a lithium source, an aluminum source, a titanium source, a phosphorus source and an alcohol solvent are mixed according to a stoichiometric ratio, the solvent is evaporated, first-stage low-temperature pre-sintering is carried out in an air atmosphere, then second-stage high-temperature sintering is carried out after uniform grinding, the obtained powder is added with a fused salt and uniformly mixed, third-stage low-temperature sintering is carried out, and finally, nanoscale lithium aluminum titanium phosphate powder is obtained after washing and drying. In the preparation process, a low-temperature fused salt is introduced, so that dissolution and recrystallization occur at the grain boundaries of nanoscale agglomerates formed after high-temperature sintering, meanwhile, the low temperature does not promote the growth of the crystal grains, so that nanoscale lithium aluminum titanium phosphate solid electrolyte powder with controllable particle size (200-400 nm) and uniform distribution is obtained.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery solid electrolyte material preparation technology, specifically a method for preparing nanoscale lithium titanium aluminum phosphate solid electrolyte powder. Background Technology

[0002] Solid-state lithium-ion batteries represent one of the future directions for rechargeable batteries, and the design of solid electrolytes is a crucial research topic. Currently, a mature solid electrolyte suitable for practical solid-state batteries is still lacking. Solid-state electrolytes are mainly classified into organic, inorganic, and composite solid electrolytes. Organic solid electrolytes, due to inherent problems such as low conductivity and poor mechanical strength, are difficult to use alone in room-temperature solid-state lithium-ion batteries. While research has shown that inorganic ceramic solid electrolytes can optimize their conductivity to liquid-like levels, they suffer from poor ductility, difficulty in processing, and poor air stability, making the commercial application of pure inorganic solid electrolytes challenging. Therefore, composite solid electrolytes combining both organic and inorganic solid electrolytes represent the most commercially promising technological approach for solid-state lithium-ion batteries.

[0003] Regarding the selection of solid electrolytes, after long-term exploration and development, inorganic ceramic solid electrolytes currently have several research hotspots, including NASICON type (such as LATP), sulfide type, and garnet type (such as LLZTO). Sulfide solid electrolytes have the highest ionic conductivity, but they suffer from poor air stability, poor solvent compatibility, and a low electrochemical window, making commercialization difficult. LLZTO has relatively high ionic conductivity, but it contains precious metals, resulting in high cost, and it readily forms a lithium carbonate passivation layer in air, significantly reducing its ionic conductivity. LATP, however, has a relatively high ionic conductivity (10... -4 ~10 -3 With its low raw material cost and excellent air / water stability, it is not only an excellent choice for inorganic ionic conductors in composite solid electrolytes, but can also be used as a positive electrode coating material or slurry additive to improve the electrochemical performance of the positive electrode. Therefore, it has great application prospects in lithium-ion batteries.

[0004] Currently, commonly used methods for preparing LATP include high-temperature solid-phase method, sol-gel method, co-precipitation method, etc. However, these methods are difficult to achieve low-cost batch preparation of nanoparticles with controllable particle size, and are prone to agglomeration, which is not conducive to promoting its industrial application. Summary of the Invention

[0005] This invention primarily provides a method for preparing nano-sized lithium aluminum titanium phosphate solid electrolyte powder. Based on high-temperature solid-state sintering, this method involves low-temperature molten salt post-treatment of the nano-aggregates to induce dissolution and recrystallization at the grain boundaries. Residual molten salt is removed by water washing, and the powder is dried to obtain nano-sized lithium aluminum titanium phosphate solid electrolyte powder with controllable particle size and good dispersion. This method has significant effects on the preparation of ultrathin composite solid electrolyte membranes and ultrathin coating of solid electrolytes onto separators. This invention achieves the above objectives through the following technical solutions:

[0006] A method for preparing nano-sized lithium aluminum titanium phosphate solid electrolyte powder includes the following steps:

[0007] Step (1): Mix the lithium source, aluminum source, titanium source and phosphorus source according to the stoichiometric ratio, and add alcohol solvent to grind and mix the materials.

[0008] Step (2): Remove the solvent from the mixture obtained by grinding and dry it to obtain precursor powder;

[0009] Step (3): The precursor is sintered at 300-500℃ in air atmosphere for 2-4 hours and then ground into powder.

[0010] Step (4): The pre-fired powder is heated to 700-900℃ in air atmosphere and sintered for 4-8 hours, then ground into powder.

[0011] Step (5): The sintered lithium titanium aluminum phosphate powder is ground and mixed with molten salt, and then the mixture is heated to 400-600℃ and sintered for 1-4 hours.

[0012] Step (6) involves washing and drying the calcined product to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0013] Furthermore, the stoichiometric ratio described in step (1) satisfies the following general chemical formula: Li 1+x Al x Ti 2-x (PO4)3, where 0.3≤x≤0.5.

[0014] Further, the lithium source mentioned in step (1) is one or more of lithium oxide, lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate and lithium nitrate; the aluminum source is one or more of aluminum oxide, aluminum nitrate, aluminum hydroxide and aluminum carbonate; the titanium source is one or more of titanium dioxide, tetrabutyl titanate, tetraethyl titanate and isopropyl titanate; the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate; and the alcohol solvent is one or more of anhydrous ethanol, isopropanol and ethylene glycol.

[0015] Furthermore, the mass ratio of the solid powder to the alcohol solvent in step (1) is 0.5 to 3.

[0016] Furthermore, the mixing method described in step (1) can be mechanical ball milling or hand milling.

[0017] Furthermore, the method for removing the solvent described in step (2) can be evaporation and drying at 60-80℃, or centrifugation or filtration followed by drying at room temperature.

[0018] Furthermore, the heating rate described in step (3) is 0.5-5℃ / min, preferably 1-2℃ / min.

[0019] Furthermore, the heating rate described in step (4) is 1-6℃ / min, preferably 2-5℃ / min.

[0020] Further, the molten salt mentioned in step (5) is one or a combination of lithium hydroxide, lithium sulfate, sodium chloride, potassium chloride, lithium nitrate, sodium nitrate, and potassium nitrate. Preferably, lithium hydroxide and lithium sulfate are mixed in a mass ratio of 1-2:1-2, and more preferably, lithium hydroxide and lithium sulfate are mixed in a mass ratio of 1:1-1.2. The inventors have found that the molten salt mixed in the above manner is more advantageous for uniform particle size distribution. The possible reason is that the combination of these two molten salts can form a eutectic solvent, which reduces the reaction temperature during molten salt treatment.

[0021] Furthermore, the mass ratio of lithium titanium aluminum phosphate powder to molten salt in step (5) is 0.5-2:1, preferably 1:1.

[0022] Furthermore, the heating rate described in step (5) is 4-6 °C / min.

[0023] Compared with existing technologies, the technical solution of this invention first obtains well-crystallized micron-sized lithium titanium aluminum phosphate secondary particles through multi-stage sintering. Then, through low-temperature molten salt treatment, the molten salt permeates between the generated powder particles, dissolving the grain boundaries of the agglomerated secondary particles and eliminating the interconnections between particles. Furthermore, the micron-sized lithium titanium aluminum phosphate secondary particles undergo a "dissolution-recrystallization" process in the molten salt. At low temperatures, the growth kinetics of recrystallized nanoparticles are slow, resulting in well-dispersed, controllable-size nano-lithium titanium aluminum phosphate particles. This solves the problems of uneven nanoparticle size and severe agglomeration in existing preparation methods, while avoiding the high cost and decreased crystallinity associated with mechanical ball milling for nano-sizing. The method is simple and easily achievable for mass production. The prepared nano-sized lithium titanium aluminum phosphate solid electrolyte material can be used in the preparation of composite solid electrolyte membranes, separator coatings, or batteries, achieving more uniform dispersion and thinner coatings.

[0024] This invention introduces low-temperature molten salt into the preparation process, causing dissolution and recrystallization at the grain boundaries of the nano-aggregates formed after high-temperature sintering. Simultaneously, the low temperature does not promote grain growth, thus obtaining nanoscale lithium aluminum titanium phosphate solid electrolyte powder with controllable particle size (200-400 nm) and uniform distribution. This invention solves the problems of particle agglomeration after traditional solid-state sintering and uneven particle size distribution caused by mechanical ball milling through simple molten salt post-treatment. The obtained nanoparticles have broad application prospects in areas such as coating solid electrolytes on membrane surfaces and the mass production of composite solid electrolyte membranes. Attached Figure Description

[0025] Figure 1 This is a SEM image of the lithium aluminum titanium phosphate powder prepared in the comparative example.

[0026] Figure 2 The image shows the XRD pattern of the nanoscale lithium titanium aluminum phosphate obtained in Example 1.

[0027] Figure 3 This is a SEM image of the nanoscale lithium titanium aluminum phosphate obtained in Example 1.

[0028] Figure 4 The image shows the particle size distribution of nano-sized lithium titanium aluminum phosphate obtained in Example 1.

[0029] Figure 5 This is a TEM image of the nanoscale lithium titanium aluminum phosphate obtained in Example 1. Detailed Implementation

[0030] The following will further illustrate the above-described embodiments of the present invention with reference to specific examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention, and all technologies based on the above content of the present invention fall within the scope of the present invention.

[0031] Comparative Example

[0032] According to Li 1.4 Al 0.4 Ti 1.6 Weigh out 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate balls according to the stoichiometric ratio of (PO4)3. Mix and grind them evenly. Heat the mixture in air at a heating rate of 1℃ / min to 400℃. After sintering for 3 hours, allow it to cool naturally to room temperature. Grind the mixture into powder and perform a second sintering. Heat the mixture in air at a heating rate of 2℃ / min to 850℃. After calcining for 5 hours, allow it to cool naturally to room temperature and grind it to obtain lithium titanium aluminum phosphate solid electrolyte powder.

[0033] Example 1

[0034] According to Li 1.4 Al 0.4 Ti1.6 The stoichiometric ratio of (PO4)3 was determined by weighing 2.28 g of lithium carbonate, 0.80 g of alumina, 5.00 g of titanium dioxide, and 13.50 g of ammonium dihydrogen phosphate spheres, mixing them together, and adding 20 g of ethanol. The mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was then heated to 400°C in air at a rate of 1°C / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder for a second stage of sintering. The temperature was increased to 850°C in air at a rate of 2°C / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15 g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 3.5 g of lithium hydroxide and 4 g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed thoroughly. The mixture was then heated to 550°C at a rate of 5°C / min and sintered for 1 hour. The product was washed three times with deionized water and dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder. 1.4 Al 0.4 Ti 1.6 (PO4)3.

[0035] Example 2

[0036] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 7g of lithium hydroxide and 8g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 550℃ at a heating rate of 5℃ / min and sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0037] Example 3

[0038] According to Li 1.4 Al 0.4 Ti 1.62.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 14g of lithium hydroxide and 16g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 550℃ at a heating rate of 5℃ / min and sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0039] Example 4

[0040] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 7g of lithium hydroxide and 8g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 500℃ at a heating rate of 5℃ / min and sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0041] Example 5

[0042] According to Li 1.4 Al 0.4 Ti 1.62.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 7g of lithium hydroxide and 8g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 600℃ at a heating rate of 5℃ / min and sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0043] Example 6

[0044] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 7g of lithium hydroxide and 8g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 550℃ at a heating rate of 5℃ / min and sintered for 0.5 hours. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0045] Example 7

[0046] According to Li 1.4 Al 0.4 Ti 1.62.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 7g of lithium hydroxide and 8g of lithium sulfate were added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 550℃ at a heating rate of 5℃ / min and sintered for 2 hours. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0047] Example 8

[0048] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 15g of lithium hydroxide was added to the lithium titanium aluminum phosphate powder, and the temperature was increased to 650℃ at a heating rate of 5℃ / min. The product was sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0049] Example 9

[0050] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 15g of lithium sulfate was added to the lithium titanium aluminum phosphate powder, and the temperature was increased to 650℃ at a heating rate of 5℃ / min. The product was sintered for 1 hour. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0051] Example 10

[0052] According to Li 1.4 Al 0.4 Ti 1.6 2.28g of lithium carbonate, 0.80g of alumina, 5.00g of titanium dioxide, and 13.50g of ammonium dihydrogen phosphate spheres were weighed and mixed according to the stoichiometric ratio of (PO4)3. 20g of ethanol was added, and the mixture was ground and mixed for 4 hours. The solvent was evaporated to obtain the precursor, which was heated to 400℃ in air at a heating rate of 1℃ / min and sintered for 3 hours. After naturally cooling to room temperature, the precursor was ground into powder and subjected to a second stage of sintering. The temperature was increased to 850℃ in air at a heating rate of 2℃ / min and calcined for 5 hours. After naturally cooling to room temperature, the precursor was ground to obtain 15g of lithium titanium aluminum phosphate solid electrolyte powder. Then, 15g of sodium chloride was added to the lithium titanium aluminum phosphate powder and mixed evenly. The temperature was increased to 650℃ at a heating rate of 5℃ / min and sintered for 0.5 hours. The product was washed three times with deionized water and then dried to obtain nano-sized lithium titanium aluminum phosphate solid electrolyte powder.

[0053] The difference between Examples 2-10 and Example 1 lies in some experimental parameters, as detailed in Table 1.

[0054] Table 1 Parameters of the Example

[0055]

[0056]

[0057] Experimental results

[0058] 1.5 g of lithium aluminum titanium phosphate solid electrolyte powder obtained from the comparative example and the embodiment was weighed and mixed with 857 μL of 5 wt% polyvinyl alcohol aqueous solution and ground until the solvent was completely evaporated. The mixture was then pressed into circular sheets under 10 MPa pressure and calcined in a muffle furnace at 1000 °C for 12 h at a rate of 5 °C / min to obtain solid electrolyte ceramic sheets. The mass of the solid to be tested was measured in air and in anhydrous ethanol using the Archimedes' displacement method. The density of the solid electrolyte was calculated according to the following formula: where ρ is the density of the solid to be tested (g·cm³). -3 A - Mass of the solid to be tested in air (g); B - Mass of the solid to be tested in anhydrous ethanol (g); ρ L - The density of anhydrous ethanol (0.789 g·cm³) -3 );ρ A -Air density (0.0012 g·cm³) -3 ).

[0059]

[0060] At room temperature, the examples and comparative samples were coated with 5nm thick platinum on both sides, and then steel sheets were added to both sides to assemble the batteries. AC impedance testing was performed using an electrochemical workstation. The ionic conductivity of each sample was obtained by fitting an equivalent circuit, as shown in Table 2. Table 2 shows that the nano-sized lithium aluminum titanium phosphate ceramic sheets have high density and their room temperature ionic conductivity can reach 10. -4 The S / cm value is higher than that of the lithium aluminum titanium phosphate in the comparative example, which has a lower ceramic sheet density due to uneven particle size and a room temperature ionic conductivity of only 8.85 × 10⁻⁶. -5 S / cm.

[0061] Table 2 Performance Characterization

[0062]

[0063]

[0064] Depend on Figure 1 The results show that even after ball milling, the particle size of lithium titanium aluminum phosphate powder in the comparative example was not completely reduced to within micrometers, and the particle size distribution was uneven, ranging from hundreds of nanometers to several micrometers. Therefore, this result indicates that it is still very difficult to prepare nanoscale lithium titanium aluminum phosphate with uniform particle size through solid-state sintering and mechanical ball milling. This will also lead to porosity and decreased density during the firing process of ceramic sheets.

[0065] from Figure 2 As can be seen, the XRD pattern of the nanoscale lithium titanium aluminum phosphate obtained in Example 1 matches the peak positions in the standard PDF card, indicating that the obtained lithium titanium aluminum phosphate does not contain other impurities. Meanwhile, from... Figure 3 The scanning results show that the lithium titanium aluminum phosphate particles obtained after molten salt treatment are nanoscale with a narrow particle size distribution and good morphology. Particle size distribution tests were performed on the prepared nanoscale lithium titanium aluminum phosphate particles, such as... Figure 4 As shown, its D10 is 170nm, D50 is 355nm, and D90 is 640nm.

[0066] Furthermore, analysis using transmission electron microscopy reveals that... Figure 5 The particles in the sample have good crystallinity and a lattice spacing of 0.364 nm, which corresponds to the (113) crystal plane of lithium titanium aluminum phosphate.

Claims

1. A method for preparing nano-sized lithium aluminum titanium phosphate solid electrolyte powder, characterized in that, Includes the following steps: Step (1): Mix the lithium source, aluminum source, titanium source and phosphorus source according to the stoichiometric ratio, and add alcohol solvent to grind and mix the materials; Step (2): Remove the solvent from the mixture obtained by grinding and dry it to obtain precursor powder; Step (3): The precursor is sintered at 300-500℃ in air atmosphere for 2-4 hours and then ground into powder. Step (4): The pre-fired powder is heated to 700-900℃ in air atmosphere and sintered for 4-8 hours, then ground into powder; Step (5): Grind and mix the sintered lithium titanium aluminum phosphate powder with molten salt, and then heat the mixture to 400-600℃ and sinter for 1-4 hours; Step (6): After washing and drying the calcined product, nano-sized lithium titanium aluminum phosphate solid electrolyte powder is obtained.

2. The preparation method according to claim 1, characterized in that, The stoichiometric ratio described in step (1) satisfies the following general chemical formula: Li 1+x Al x Ti 2-x (PO4)3, where 0.3≤x≤0.

5.

3. The preparation method according to claim 1, characterized in that, The lithium source mentioned in step (1) is one or more of lithium oxide, lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate and lithium nitrate; the aluminum source is one or more of aluminum oxide, aluminum nitrate, aluminum hydroxide and aluminum carbonate; the titanium source is one or more of titanium dioxide, tetrabutyl titanate, tetraethyl titanate and isopropyl titanate; the phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate; and the alcohol solvent is one or more of anhydrous ethanol, isopropanol and ethylene glycol.

4. The preparation method according to claim 1, characterized in that, In step (1), the total mass ratio of lithium source, aluminum source, titanium source, phosphorus source and alcohol solvent is 0.5~3.

5. The preparation method according to claim 1, characterized in that, The heating rate in step (3) is 0.5-5℃ / min; the heating rate in step (4) is 1-6℃ / min.

6. The preparation method according to claim 5, characterized in that, The heating rate mentioned in step (3) is 1-2℃ / min, and the heating rate mentioned in step (4) is 2-5℃ / min.

7. The preparation method according to claim 1, characterized in that, The molten salt mentioned in step (5) is one or a combination of lithium hydroxide, lithium sulfate, sodium chloride, potassium chloride, lithium nitrate, sodium nitrate, and potassium nitrate.

8. The preparation method according to claim 1, characterized in that, The molten salt mentioned in step (5) is a mixture of lithium hydroxide and lithium sulfate in a mass ratio of 1-2:1-2.

9. The preparation method according to claim 1, characterized in that, The molten salt mentioned in step (5) is a mixture of lithium hydroxide and lithium sulfate in a mass ratio of 1:1-1.

2.

10. The preparation method according to claim 1, characterized in that, The mass ratio of lithium titanium aluminum phosphate powder to molten salt in step (5) is 0.5-2:

1.

11. The preparation method according to claim 10, characterized in that, The mass ratio of lithium titanium aluminum phosphate powder to molten salt in step (5) is 1-1.5:

1.

12. The preparation method according to claim 1, characterized in that, The heating rate mentioned in step (5) is 4-6℃ / min.

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