Lithium lanthanum zirconium oxide nanoparticles and a method for preparing the same

Abstract

The application discloses lithium lanthanum zirconium oxide nanoparticles and a preparation method thereof. The preparation method of the lithium lanthanum zirconium oxide nanoparticles is as follows: firstly, a dry gel containing zirconium and lanthanum is prepared, and then the dry gel is crushed and mixed with an excessive lithium source and calcined below 700 DEG C. The excessive lithium source is converted into lithium carbonate by reacting with pyrolysis products of the gel or carbon dioxide in the air during high-temperature calcination. During the sintering process, the excessive solid lithium carbonate serves as a reaction reagent and simultaneously plays a role of isolating and dispersing the lithium lanthanum zirconium oxide nanoparticles, so that the generated lithium lanthanum zirconium oxide is inhibited from excessively growing under high-temperature conditions. Finally, the lithium carbonate is removed, and the lithium lanthanum zirconium oxide nanoparticles with high dispersion and an average particle size less than 200 nm can be obtained. The application has the advantages of simple process and easy scaling.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a solid electrolyte material for a solid-state lithium ion battery, in particular to a preparation method of lithium lanthanum zirconium oxide nanoparticles, and further relates to the lithium lanthanum zirconium oxide nanoparticles obtained by the method. BACKGROUND

[0002] Different from the liquid medium system of the traditional lithium ion battery, the new lithium ion battery technology adopts a solid electrolyte to replace the traditional electrolyte and diaphragm assembly, thereby simplifying the structure, significantly enhancing the battery thermal stability, widening the use temperature range, having higher energy density, and significantly improving the safety performance of the battery, thereby guiding the mainstream trend of the lithium battery industry development.

[0003] Among various solid electrolyte systems, the garnet-type cubic-phase lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , abbreviated as LLZO) solid electrolyte has attracted extensive attention due to its excellent comprehensive performance. The material exhibits high room-temperature ionic conductivity, excellent electrochemical stability and high electrochemical window, and is considered by the industry as one of the most promising mainstream solid electrolyte materials for industrialization.

[0004] The controllable preparation of the LLZO solid electrolyte and raw material powder still faces major challenges. Existing researches prove that the smaller the grain size of the LLZO solid electrolyte is, the better the performance is. The nanoscale LLZO particles can improve the ionic conductivity and cycle stability, accelerate the transmission process of lithium ions at the interface, and also can greatly improve the interface contact and lithium dendrite growth. However, the preparation of the LLZO powder at present mainly depends on the solid-phase reaction method, but the method has problems such as uneven mixing of raw materials, grain coarsening caused by high-temperature calcination, and the like, and the product particle size is as high as tens of microns. Although the wet chemical method (such as sol-gel method, coprecipitation method, etc.) can prepare LLZO particles with relatively smaller particle size, the particle size is also difficult to reach below 1 micron due to the same need for high-temperature calcination.

[0005] CN 111204800 A discloses a preparation method of lanthanum zirconate nanoparticles, which uses a water-soluble salt-assisted sol-gel method. An organic sol containing zirconium and lanthanum is used to impregnate a water-soluble salt and undergo gel transformation. The gel containing zirconium and lanthanum shrinks and forms a layer of xerogel film on the surface of the water-soluble salt particles. The gel film decomposes at high temperature to form dispersed lanthanum zirconate nanoparticles, thereby obtaining highly dispersed lanthanum zirconate nanoparticles. However, this scheme is not suitable for preparing LLZO, because if the raw material contains lithium salt, the lithium salt with a lower melting point will co-crystallize and melt with the isolation salt (potassium sulfate, sodium chloride or sodium sulfate) during high-temperature calcination, and the isolation salt cannot maintain the solid salt particle state. CN 117756175 A discloses a nano lithium lanthanum zirconium oxide powder and its preparation method and application. The particle size of lithium lanthanum zirconium oxide is controlled to nanoscale by controlling the heating rate, but the sintering step takes 6-18 hours, which increases energy consumption and is low in efficiency.

[0006] In summary, the prior art cannot solve the problem of high-temperature sintering and growth of LLZO particles during preparation, and there is an urgent need to develop an efficient preparation method of LLZO nanoparticles to promote the technical progress of solid-state lithium battery industry. SUMMARY

[0007] Technical problem: The purpose of the present application is to provide a preparation method of lithium lanthanum zirconium oxide nanoparticles that can solve the problem of high-temperature sintering and growth of lithium lanthanum zirconium oxide particles. Another purpose of the present application is to provide lithium lanthanum zirconium oxide nanoparticles prepared by the method.

[0008] Technical solution: The present application provides a preparation method of lithium lanthanum zirconium oxide nanoparticles, which comprises the following steps:

[0009] (1) A dry gel containing a lanthanum source and a zirconium source is prepared according to the elemental molar ratio n(La): n(Zr) = 2.8-3.2:2, and is crushed;

[0010] (2) A lithium source with a melting point below 500°C is mixed with the crushed dry gel according to the elemental molar ratio n(Li) / n(Zr) > 3.5;

[0011] (3) The mixture obtained in step (2) is calcined at a temperature above 550°C and below 700°C in air to form lithium lanthanum zirconium oxide nanoparticles and lithium carbonate;

[0012] (4) The lithium carbonate is removed to obtain lithium lanthanum zirconium oxide nanoparticles.

[0013] Preferably, in step (1), the lanthanum source is at least one of lanthanum nitrate and lanthanum acetate, and the zirconium source is at least one of lanthanum nitrate, lanthanum acetate, zirconium n-propylate and zirconium isopropylate.

[0014] Preferably, in step (2), the lithium source is lithium hydroxide or a blend of lithium hydroxide and lithium carbonate, 10.5 ≥ n(Li) / n(Zr) ≥5.25. More preferably, in order to ensure the particle size range and uniformity, and avoid raw material waste, in step (2), 10.5 ≥ n(Li) / n(Zr) ≥7.

[0015] Preferably, in step (2), the mixed dry gel is ground by at least one of a mortar, a ball mill, and a sand mill, and the particle size of the ground dry gel and / or the mixture obtained in step (2) is not more than 100 μm.

[0016] Preferably, in order to reduce the generation of impurities and avoid uneven particle size, in step (3), the calcination temperature is 620-680 ℃, and the calcination time is 0.8-2 hours.

[0017] Preferably, in step (4), lithium carbonate is removed by using a weak acid aqueous solution, and the weak acid is at least one of citric acid, acetic acid, tartaric acid, malic acid, and oxalic acid.

[0018] Preferably, the method for preparing the dry gel comprises: dissolving a lanthanum source and a zirconium source in an organic solvent, and generating a gel by incubating at 60-100 ℃ for more than 1 hour, and then air-drying and / or oven-drying to obtain the dry gel, and the organic solvent is at least one of n-propanol, isopropanol, ethanol, n-butanol, ethylene glycol, ethylene glycol methyl ether, propylene glycol, ethylene glycol ethyl ether, and ethylene glycol butyl ether.

[0019] The lithium lanthanum zirconium oxide nanoparticles prepared by the method have an average particle size of less than 200 nm.

[0020] The present application grinds and mixes the zirconium lanthanum dry gel powder with excess lithium hydroxide, and calcines below the melting point of lithium carbonate. During the calcination process, the dry gel powder is thermally decomposed to generate a zirconium lanthanum compound and release carbon dioxide, the carbon dioxide reacts with lithium hydroxide to generate lithium carbonate, the zirconium lanthanum compound reacts with lithium carbonate to generate lithium lanthanum zirconium oxide nanoparticles, and the excess lithium carbonate serves to isolate and disperse the lithium lanthanum zirconium oxide nanoparticles, thereby inhibiting sintering and growth of the lithium lanthanum zirconium oxide nanoparticles at high temperatures. After washing the calcination product with a weak acid and removing the lithium carbonate, dispersed lithium lanthanum zirconium oxide nanoparticles can be obtained. This method can avoid high-temperature sintering and growth of the lithium lanthanum zirconium oxide nanoparticles, and prepare highly dispersed lithium lanthanum zirconium oxide nanoparticles with an average particle size of less than 200 nm.

[0021] Beneficial effects: compared with the prior art, the present application has the following advantages: 1, the obtained lithium lanthanum zirconium oxide nanoparticles have an average particle size of less than 200 nm and good dispersibility, effectively avoiding the problem of sintering growth at high temperature; 2, the process of the present application is very simple, and there is no need to regulate the content and flow of sintering atmosphere, and the reaction can be carried out under open or closed conditions, the reaction time is short, and it is suitable for batch production. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The transmission electron microscope image of the lithium lanthanum zirconium oxide nanoparticles prepared according to the scheme of example 1 of the present application is shown in the figure.

[0023] Figure 2 The XRD pattern of the lithium lanthanum zirconium oxide nanoparticles obtained according to the scheme of example 1 of the present application is shown in the figure.

[0024] Figure 3 The transmission electron microscope image of the lithium lanthanum zirconium oxide nanoparticles prepared according to the scheme of example 10 of the present application is shown in the figure.

[0025] Figure 4 The XRD pattern of the lithium lanthanum zirconium oxide nanoparticles obtained according to the scheme of example 10 of the present application is shown in the figure.

[0026] Figure 5 The transmission electron microscope image of the lithium lanthanum zirconium oxide nanoparticles prepared according to the scheme of example 11 of the present application is shown in the figure.

[0027] Figure 6 The picture of the lithium lanthanum zirconium oxide particle sample prepared according to the scheme of comparative example 1 of the present application is shown in the figure.

[0028] Figure 7 The scanning electron microscope image of the lithium lanthanum zirconium oxide particle prepared according to the scheme of comparative example 1 of the present application is shown in the figure.

[0029] Figure 8 The transmission electron microscope image of the lithium lanthanum zirconium oxide particle prepared according to the scheme of comparative example 2 of the present application is shown in the figure. DETAILED DESCRIPTION

[0030] The scheme of the present application will be described in detail below in combination with examples.

[0031] In the present application, lanthanum zirconium xerogel powder and lithium hydroxide are mixed by grinding to form a mixture of lanthanum zirconium gel particles and lithium hydroxide particles. During calcination, the lanthanum zirconium gel particles are first decomposed to form lanthanum zirconium compounds (main phase is lanthanum zirconate with pyrochlore structure), releasing a large amount of carbon dioxide, and a large number of pores are formed around the lanthanum zirconium compound particles. At 400-500°C, lithium hydroxide (melting point 462°C) melts and wets the lanthanum zirconium compound particles, and at the same time, lithium hydroxide reacts with carbon dioxide released by gel thermal decomposition or carbon dioxide in the air to form lithium carbonate, forming a state in which lithium carbonate salt separates and disperses lanthanum zirconium compound particles. At 550°C, the lanthanum zirconium compound and the surrounding lithium carbonate react to form a lithium lanthanum zirconium oxide phase, and the excess solid lithium carbonate salt still maintains the state of separating and dispersing lithium lanthanum zirconium oxide nanoparticles. When calcined below the melting point of lithium carbonate (720°C) (700°C), lithium lanthanum zirconium oxide nanoparticles are always separated and dispersed by solid lithium carbonate salt, so the high-temperature sintering and growth of lithium lanthanum zirconium oxide particles can be effectively inhibited. When the calcination temperature exceeds 700°C, the lithium carbonate salt will melt, and the lithium lanthanum zirconium oxide particles will quickly grow to several microns to tens of microns in the lithium carbonate melt. Therefore, the calcination temperature of the present application is not higher than 700°C.

[0032] The present research group has not found any reports of similar technology in the literature, and has not found any reports of using the above mechanism to prepare lithium lanthanum zirconium oxide nanoparticle materials in the known technical means in the field.

[0033] The following are specific examples.

[0034] Example 1: Lanthanum nitrate and zirconium nitrate were dissolved in ethylene glycol methyl ether, and the molar ratio of lanthanum element to zirconium element was 3:2. The gel was formed after 80°C heat preservation for 1 hour, and the xerogel was prepared. After the xerogel was crushed to a particle size of ≤100 μm, 10 grams were weighed and mixed with 1.75 grams of anhydrous lithium hydroxide by grinding. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element excess 50%). The ground mixture was calcined at 650°C for 1 hour or more, and after cooling, it was washed with a citric acid aqueous solution and then with deionized water for 2-3 times. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained. The transmission electron microscope detection results of the lithium lanthanum zirconium oxide nanoparticles obtained in this example are shown in Figure 1 The size is uniform, the average particle size is less than 200 nm, the particle shape is round, the surface is smooth, and the dispersion is good. The XRD detection results are shown in Figure 2 The garnet-type cubic phase.

[0035] Example 2: Dry gel was prepared by sol-gel method using lanthanum nitrate, zirconium acetate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After being crushed, 10 grams of dry gel was mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element was 50% excessive). The mixture was loaded into a crucible and covered, and calcined at 650°C for more than 1 hour. After being cooled, the mixture was washed with citric acid aqueous solution and deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles with an average particle size less than 200 nm were obtained.

[0036] Example 3: Dry gel was prepared by sol-gel method using lanthanum acetate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After being crushed, 10 grams of dry gel was mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element was 50% excessive). The mixture was loaded into a crucible, and the crucible was not covered, and calcined at 650°C for more than 1 hour. After being cooled, the mixture was washed with citric acid aqueous solution and deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles with an average particle size less than 200 nm were obtained.

[0037] Example 4: Dry gel was prepared by sol-gel method using lanthanum nitrate, zirconium n-propylate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After being crushed, 10 grams of dry gel was mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element was 50% excessive). The mixture was calcined at 650°C for more than 1 hour. After being cooled, the mixture was washed with citric acid aqueous solution and deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0038] Example 5: Dry gel was prepared by sol-gel method using lanthanum nitrate, zirconium isopropylate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After being crushed, 10 grams of dry gel was mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element was 50% excessive). The mixture was calcined at 650°C for more than 1 hour. After being cooled, the mixture was washed with citric acid aqueous solution and deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0039] Example 6: Using lanthanum acetate, zirconium isopropoxide and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element is 3:2. The xerogel is prepared by the sol-gel method as in Example 1. After being crushed, 10 grams of the xerogel is mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture is 5.25:1 (lithium element is 50% excessive). The mixture is calcined at 650°C for more than 1 hour. After being cooled, the mixture is washed with a citric acid aqueous solution and then with deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles are obtained.

[0040] Example 7: Using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element is 3:2. The xerogel is prepared by the sol-gel method as in Example 1. After being crushed, 10 grams of the xerogel is mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture is 7:1 (lithium element is 100% excessive). The mixture is calcined at 650°C for 2 hours. After being cooled, the mixture is washed with a citric acid aqueous solution and then with deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles are obtained.

[0041] Example 8: Using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element is 3:2. The xerogel is prepared by the sol-gel method as in Example 1. After being crushed, 10 grams of the xerogel is mixed with 3.5 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture is 10.5:1 (lithium element is 200% excessive). The mixture is calcined at 650°C for 2 hours. After being cooled, the mixture is washed with a citric acid aqueous solution and then with deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles are obtained.

[0042] Example 9: Using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element is 3:2. The xerogel is prepared by the sol-gel method as in Example 1. After being crushed, 10 grams of the xerogel is mixed with 4.67 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture is 14:1 (lithium element is 300% excessive). The mixture is calcined at 650°C for 2 hours. After being cooled, the mixture is washed with a citric acid aqueous solution and then with deionized water for 2-3 times. After being dried, dispersed lithium lanthanum zirconium oxide nanoparticles are obtained.

[0043] Example 10: Dry gel was prepared by sol-gel method as in Example 1 using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After crushing, 10 grams of dry gel was mixed with 1.75 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 5.25:1 (lithium element excess 50%). The mixture was calcined at 600°C for 2 hours. After cooling, the mixture was washed with aqueous citric acid solution, and then washed with deionized water for 2-3 times. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained. The transmission electron microscope detection results of the lithium lanthanum zirconium oxide nanoparticles prepared in this example are shown in FIG. 6. The small square-shaped nanoparticles are lanthanum zirconate phase, and the XRD detection results are shown in FIG. 7. When calcined at 600°C or below, square-shaped lanthanum zirconate nanoparticles are easily left over. Figure 3 Figure 4

[0044] Example 11: Dry gel was prepared by sol-gel method as in Example 1 using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After crushing, 10 grams of dry gel was mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 7:1 (lithium element excess 100%). The mixture was calcined at 700°C for 2 hours. After cooling, the mixture was washed with aqueous citric acid solution, and then washed with deionized water for 2-3 times. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained. The transmission electron microscope detection results of the lithium lanthanum zirconium oxide nanoparticles prepared in this example are shown in FIG. 8. At 700°C, since the temperature is close to the melting point of lithium carbonate, the size of the obtained lithium lanthanum zirconium oxide particles is relatively large, and the uniformity is poor. Figure 5

[0045] Example 12: Dry gel was prepared by sol-gel method as in Example 1 using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After crushing, 10 grams of dry gel was mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 7:1 (lithium element excess 100%). The mixture was calcined at 650°C for 2 hours. After cooling, the mixture was washed with aqueous tartaric acid solution, and then washed with deionized water for 2-3 times. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0046] Example 13: Dry gel was prepared by sol-gel method as in Example 1 using lanthanum nitrate, zirconium nitrate and ethylene glycol methyl ether as raw materials, the molar ratio of lanthanum element to zirconium element was 3:2. After crushing, 10 grams of dry gel was mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium element to zirconium element in the mixture was 7:1 (lithium element excess 100%). The mixture was calcined at 650°C for 2 hours. After cooling, the mixture was washed with aqueous oxalic acid solution, and then washed with deionized water for 2-3 times. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0047] ​​​Example 14: Using lanthanum nitrate, zirconium nitrate, and ethylene glycol methyl ether as raw materials, with a molar ratio of lanthanum to zirconium of 3:2, a dry gel was prepared using the sol-gel method as in Example 1. 10 grams of the gel was pulverized and weighed, then ground and mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium to zirconium in the mixture was 7:1 (100% lithium excess). The ground mixture was calcined at 650°C for 2 hours, cooled, washed with an aqueous acetic acid solution, and then washed 2-3 times with deionized water. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0048] Example 15: Using lanthanum nitrate, zirconium nitrate, and ethylene glycol methyl ether as raw materials, with a molar ratio of lanthanum to zirconium of 3:2, a dry gel was prepared using the sol-gel method as in Example 1. 10 grams of the gel was pulverized and weighed, then ground and mixed with 2.33 grams of anhydrous lithium hydroxide. The molar ratio of lithium to zirconium in the mixture was 7:1 (100% lithium excess). The ground mixture was calcined at 650°C for 2 hours, cooled, washed with malic acid aqueous solution, and then washed 2-3 times with deionized water. After drying, dispersed lithium lanthanum zirconium oxide nanoparticles were obtained.

[0049] Comparative Example 1: Using lanthanum nitrate, zirconium nitrate, lithium nitrate, and ethylene glycol methyl ether as raw materials, with a molar ratio of lanthanum, zirconium, and lithium of 3:2:7, a sol containing lanthanum, zirconium, and lithium was obtained. Potassium sulfate was impregnated with this sol, allowed to stand completely, and excess sol was removed. The mixture was then heated to 80°C for 1 hour to form a gel, which was subsequently dried to obtain potassium sulfate particles encapsulated in a dry gel film. A small amount was placed in a crucible and calcined at 650°C for 1 hour. The resulting sample is shown below. Figure 6 As shown, it exists in a state of molten followed by solidification. A small amount was washed with deionized water and dried to obtain lithium lanthanum zirconium oxide particles. The scanning electron microscope (SEM) results of the lithium lanthanum zirconium oxide particles are shown below. Figure 7 As shown in the SEM image, the particles are extremely large and unevenly distributed. This phenomenon occurs because the mixed salt of lithium salt and potassium sulfate has a very low melting point and melts during calcination, causing the lithium lanthanum zirconium oxide particles to grow abnormally within the molten salt.

[0050] Comparative Example 2: Using lanthanum nitrate, zirconium nitrate, and ethylene glycol methyl ether as raw materials, with a molar ratio of lanthanum to zirconium of 3:2, a dry gel was prepared by the sol-gel method. 10 grams of the gel was pulverized and weighed, then ground and mixed with 2.7 grams of anhydrous lithium carbonate. The molar ratio of lithium to zirconium in the mixture was 5.25:1 (lithium in excess by 50%). The ground mixture was calcined at 650℃ for at least 1 hour, cooled, washed with citric acid aqueous solution, and then washed 2-3 times with deionized water. After drying, lithium lanthanum zirconium oxide particles were obtained. The test results of the obtained samples are as follows... Figure 8As shown, lithium carbonate is directly introduced, and in the calcination process, since there is no low-melting-point lithium hydroxide to melt and wet the lanthanum-zirconium compound particles and enter the periphery of the lanthanum-zirconium compound particles, it is difficult to form a state in which lithium carbonate isolates the lanthanum-zirconium compound, and the lithium lanthanum-zirconium oxygen particles sinter and grow to 10 μm.

Claims

1. A method for preparing lithium lanthanum zirconium oxide nanoparticles, characterized in that, Includes the following steps: (1) Prepare a dry gel containing lanthanum source and zirconium source according to the element molar ratio n(La): n(Zr) = 2.8~3.2: 2, and then pulverize it; (2) Mix the lithium source and the pulverized dry gel according to the elemental molar ratio n(Li) / n(Zr)>3.5, wherein the melting point of the lithium source is below 500℃; (3) The mixture obtained in step (2) is calcined at a temperature above 550°C and below 700°C to generate lithium carbonate and lithium lanthanum zirconium oxide nanoparticles; (4) Remove lithium carbonate to obtain lithium lanthanum zirconium oxide nanoparticles.

2. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (1), the lanthanum source is at least one of lanthanum nitrate and lanthanum acetate, and the zirconium source is at least one of lanthanum nitrate, lanthanum acetate, zirconium n-propoxide, and zirconium isopropoxide.

3. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (2), the lithium source is lithium hydroxide or a blend of lithium hydroxide and lithium carbonate, where 10.5 ≥ n(Li) / n(Zr) ≥ 5.

25.

4. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (2), 10.5 ≥ n(Li) / n(Zr) ≥ 7.

5. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (2), at least one of a mortar, ball mill, and sand mill is used for grinding and mixing, and the particle size of the pulverized dry gel and / or the mixture obtained in step (2) does not exceed 100 μm.

6. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (3), the calcination temperature is 620~680℃ and the calcination time is 0.8~2 hours.

7. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (4), lithium carbonate is removed with a weak acid aqueous solution, wherein the weak acid is at least one of citric acid, acetic acid, tartaric acid, malic acid, and oxalic acid.

8. The method for preparing lithium lanthanum zirconium oxide nanoparticles according to claim 1, characterized in that, In step (1), the preparation method of the dry gel is as follows: lanthanum source and zirconium source are dissolved in an organic solvent, kept at 60~100℃ for more than 1 hour to generate a gel, and air-dried and / or baked to obtain a dry gel. The organic solvent is at least one of n-propanol, isopropanol, ethanol, n-butanol, ethylene glycol, ethylene glycol methyl ether, propylene glycol, ethylene glycol ethyl ether, and ethylene glycol butyl ether.

9. Lithium lanthanum zirconium oxide nanoparticles prepared by any one of claims 1 to 8.

10. The lithium lanthanum zirconium oxide nanoparticles according to claim 9, characterized in that, The average particle size of the lithium lanthanum zirconium oxide nanoparticles is less than 200 nm.

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