Monoclinic phase zirconium oxide nano powder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of superfine powder preparation and lithium battery materials, and particularly relates to monoclinic-phase zirconium oxide nano powder as well as a preparation method and application thereof. The preparation method comprises the following steps: adding zirconium oxychloride octahydrate into water for dissolving to obtain a zirconium oxychloride aqueous solution, then putting the zirconium oxychloride aqueous solution into a hydrothermal reaction kettle, heating to 140-160 DEG C for hydrothermal reaction, cooling to room temperature after the reaction is completed, and standing for precipitation; then adding ammonia water to carry out ammonolysis reaction, standing and aging, completely precipitating residual zirconium ions, separating the precipitate, washing and drying to obtain a zirconium hydroxide precursor; and finally, carrying out heat preservation calcination treatment at 850-950 DEG C in an air environment to obtain the monoclinic phase zirconium oxide nano powder. The preparation method is simple in preparation process, and toxic and harmful substances are not introduced. The obtained nano ZrO2 powder has the advantages of accurate chemical composition, small powder particle size and low Cl <-> content, and meets the specification requirements of lithium battery positive electrode material additives.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrafine powder preparation and lithium battery materials, and specifically relates to a monoclinic zirconium oxide nano powder and a preparation method and application thereof. Background Art

[0002] Zirconia (ZrO2) is a material that is resistant to high temperatures (melting point up to 2680°C), corrosion-resistant, and has high hardness (Mohs hardness of 8.5). It not only has excellent physical properties, such as high strength, high hardness, good thermal shock resistance, wear resistance, and low thermal conductivity (thermal conductivity is 2.09W / mol·K), but also has stable chemical properties, good acid and alkali corrosion resistance in oxidizing or reducing atmospheres, and even exhibits good biocompatibility. It plays a vital role in electronic products, ceramics, catalysis, and special refractory materials. In the lithium battery industry, special nano-zirconia is a high-purity nano-zirconia (purity of more than 99%), which requires nanoparticles to be fine in size, uniform in particle size distribution, no hard agglomerates, few magnetic foreign bodies, and good sphericity.

[0003] Nano ZrO2 powder has three phases: monoclinic, cubic and tetragonal. Nano ZrO2 of different phases has its own excellent performance. Among them, monoclinic ZrO2 shows good biocompatibility, good chemical stability and high dielectric constant, and plays a huge role in bone plant bio-coating, catalyst and gate dielectric layer. Cubic ZrO2 has excellent oxygen ion conductivity and is widely used in oxygen sensors and fuel cell electrolytes. Due to its phase transformation characteristics, tetragonal ZrO2 can be used as an important raw material for toughening ceramics and zirconium-containing composite materials.

[0004] So far, there are many methods for preparing nano ZrO2 powder, including precipitation method, hydrothermal method, sol-gel method, spray pyrolysis method, etc. Among them, precipitation method is difficult to control the size, morphology and chemical composition of the product; sol-gel method has a long reaction cycle, expensive raw materials, organic solvents are harmful to the human body, and it is not easy to large-scale industrial production; spray pyrolysis method has high requirements for equipment, high cost, and is not easy to process production, while hydrothermal method has a simple process, low energy consumption, and eliminates grinding and the impurities it brings.

[0005] Patent CN109354064A reported a solvothermal method to prepare monoclinic ZrO2 nanoparticles, specifically, in the absence of surfactant, using zirconol as raw material, N,N-dimethylformamide (DMF) and glacial acetic acid as mixed solvents. Although this method does not have a surfactant, it introduces two organic compounds, N,N-dimethylformamide (DMF) and glacial acetic acid, which increases production costs and difficulty. It cannot be completely removed at high temperatures, and the residual organic matter will become impurities, affecting the purity and performance of ZrO2.

[0006] Patent CN110228819A involves a method for hydrothermal synthesis of ZrO2 powder, the specific steps of which are: completely dissolving ZrOCl2·8H2O raw material in water, adding hydrogen peroxide and stirring evenly, then introducing oxygen for hydrothermal reaction, and then filtering, washing and calcining to obtain the powder. This method has a simple preparation process, but the amount of oxygen in the reaction is large and explosive.

[0007] In patent CN10187058713B, an alkaline aqueous solution of a certain concentration is added dropwise to a certain amount of zirconium salt aqueous solution, stirred evenly, washed and redispersed, and hydrothermally reacted with concentrated acid, followed by centrifugal washing to obtain monoclinic ZrO2. This method introduces concentrated acid hazardous chemicals, increasing the complexity of the process and production costs. Summary of the invention

[0008] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing monoclinic zirconium oxide nanopowder. The preparation method of the present invention uses zirconium oxychloride as a raw material and utilizes a hydrothermal-coprecipitation method to prepare monoclinic zirconium oxide nanopowder, which can simplify the preparation process, does not introduce toxic and harmful substances, and reduces the preparation requirements. The obtained nano ZrO2 powder has precise chemical composition, small powder particle size, and Cl - Advantages of lower content.

[0009] Another object of the present invention is to provide a monoclinic zirconium oxide nanopowder prepared by the above method.

[0010] Another object of the present invention is to provide the use of the above-mentioned monoclinic zirconium oxide nanopowder as an additive for lithium battery positive electrode materials.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] A method for preparing monoclinic zirconium oxide nanopowder comprises the following preparation steps:

[0013] (1) adding zirconium oxychloride octahydrate into water to dissolve it to obtain a zirconium oxychloride aqueous solution, which is then placed in a hydrothermal reaction kettle and heated to 140 to 160° C. for hydrothermal reaction. After the reaction is completed, the solution is cooled to room temperature and allowed to stand for precipitation;

[0014] (2) adding aqueous ammonia to the reaction solution of step (1) to carry out an ammonolysis reaction, allowing the solution to stand for aging to completely precipitate the remaining zirconium ions, separating the precipitate, washing it, and drying it to obtain a zirconium hydroxide precursor;

[0015] (3) The zirconium hydroxide precursor obtained in step (2) is subjected to calcination treatment at 850-950° C. in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0016] Furthermore, in step (1), the mass ratio of zirconium oxychloride octahydrate to water is 1:3-5.

[0017] Furthermore, during the hydrothermal reaction process in step (1), the filling degree of the hydrothermal reaction kettle is 70-85%.

[0018] Furthermore, the hydrothermal reaction time in step (1) is 12 to 16 hours.

[0019] Furthermore, the static precipitation time in step (1) is 0.5 to 1 hour. By static precipitation after the dissolution reaction of zirconium oxychloride octahydrate, most of the zirconium ions are precipitated, and the remaining zirconium ions remain in the supernatant.

[0020] Furthermore, the mass concentration of the ammonia water in step (2) is 25-28%.

[0021] Furthermore, in step (2), ammonia water is added to make the pH of the mixed solution be 8-10.

[0022] Furthermore, the standing aging time in step (2) is 0.5 to 1 hour.

[0023] Furthermore, the washing in step (2) refers to washing with pure water multiple times. - content.

[0024] Furthermore, the heat preservation and calcination treatment time in step (3) is 2 to 4 hours.

[0025] A monoclinic zirconium oxide nano powder is prepared by the method.

[0026] Furthermore, the D50 particle size of the monoclinic zirconium oxide nanopowder is less than 0.5 μm, - Content <200ppm.

[0027] The monoclinic zirconium oxide nanopowder is used as an additive for positive electrode materials of lithium batteries.

[0028] The reaction process of the preparation method of the present invention does not introduce other impurities, the product quality is high, and it is easy to handle. The chemical equation of the reaction process is as follows:

[0029] ZrOCl2·8H2O+H2O→ZrO(OH)2↓+2HCl+7H2O;

[0030] NH3·H2O+HCl→NH4Cl+H2O;

[0031] ZrOCl2+2NH3·H2O→ZrO(OH)2↓+2NH4Cl;

[0032] ZrO(OH)2→ZrO2+H2O.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The preparation method of the present invention uses the inorganic compound zirconium oxychloride octahydrate as a raw material and ammonia water as an auxiliary material. Without using other additives, a white, non-large particle, non-agglomerate, and non-inclusion pure monoclinic ZrO2 powder can be prepared through hydrothermal, ammonia decomposition, washing, drying, and calcination processes. The preparation process is simple and efficient, the raw materials are economical, the amount of precipitant added is small, the waste gas and waste liquid generated are easy to treat, and it has the characteristics of "green, environmentally friendly, and efficient".

[0035] (2) The present invention can precipitate more than 95% of zirconium ions by first subjecting the zirconium oxychloride aqueous solution to a hydrothermal reaction at 140-160°C; and then adding ammonia water to adjust the pH to 8-10 for an ammonia solution reaction to completely precipitate the remaining zirconium ions. On the one hand, the amount of ammonia water added as a precipitant can be reduced, and on the other hand, the precipitation rate can be controlled to make the precipitate particles fine, and the entrainment and encapsulation of chloride ions by the precipitate can be reduced, thereby reducing the particle size and chloride ion content of the final zirconium oxide nanopowder product and improving the product quality. The obtained zirconium oxide nanopowder meets the specifications required for positive electrode material additives in the lithium ion battery industry.

[0036] (3) The present invention heat-sinters the zirconium hydroxide precursor at 850-950° C. in an air environment, which can ensure that the zirconium hydroxide precursor is completely converted into monoclinic zirconium oxide, and the obtained powder particle size is relatively small. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The process flow chart of a method for preparing monoclinic zirconium oxide nanopowder of the present invention is as follows;

[0038] Figure 2 This is the XRD diagram of the monoclinic zirconium oxide nanopowder prepared in the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0040] Example 1

[0041] A method for preparing monoclinic zirconium oxide nanopowder, the process flow chart of which is as follows Figure 1 As shown, the specific preparation steps are as follows:

[0042] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 150° C., and the reaction time is 16 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0043] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 8.5, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0044] (3) The zirconium hydroxide precursor is calcined at 900° C. for 3 hours in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0045] The XRD pattern of the obtained monoclinic zirconia nanopowder is as follows: Figure 2 shown.

[0046] Example 2

[0047] A method for preparing monoclinic zirconium oxide nanopowder, the process flow chart of which is as follows Figure 1 As shown, the specific preparation steps are as follows:

[0048] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 160° C., and the reaction time is 12 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0049] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 9, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0050] (3) The zirconium hydroxide precursor is calcined at 850° C. for 3 hours in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0051] Example 3

[0052] A method for preparing monoclinic zirconium oxide nanopowder, the process flow chart of which is as follows Figure 1 As shown, the specific preparation steps are as follows:

[0053] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 150° C., and the reaction time is 12 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0054] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 10, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0055] (3) The zirconium hydroxide precursor is calcined at 900° C. for 2 hours in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0056] Example 4

[0057] A method for preparing monoclinic zirconium oxide nanopowder, the process flow chart of which is as follows Figure 1 As shown, the specific preparation steps are as follows:

[0058] (1) Weigh 22 g of raw material zirconium oxychloride octahydrate, measure 110 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 150 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 140° C., and the reaction time is 16 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 0.5 h.

[0059] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 25 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 8, the obtained solution is allowed to stand for 1 hour, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0060] (3) The zirconium hydroxide precursor is calcined at 950° C. for 2 h in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0061] Example 5

[0062] A method for preparing monoclinic zirconium oxide nanopowder, the process flow chart of which is as follows Figure 1 As shown, the specific preparation steps are as follows:

[0063] (1) Weigh 23 g of raw material zirconium oxychloride octahydrate, measure 69 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 150° C., and the reaction time is 14 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 0.75 h.

[0064] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 25 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 9, the obtained solution is allowed to stand for 0.5 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0065] (3) The zirconium hydroxide precursor is calcined at 850° C. for 4 hours in an air environment to obtain the monoclinic zirconium oxide nanopowder.

[0066] Comparative Example 1

[0067] A method for preparing zirconium oxide powder, compared with Example 1, step (2) the pH of the mixed solution is adjusted to 7 by the ammonolysis reaction, and the rest is the same. The specific preparation steps are as follows:

[0068] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 150° C., and the reaction time is 16 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0069] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 7, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0070] (3) The zirconium hydroxide precursor is calcined at 900° C. for 3 hours in an air environment to obtain the zirconium oxide powder.

[0071] Comparative Example 2

[0072] A method for preparing zirconium oxide powder, compared with Example 1, the temperature of heat preservation calcination in step (3) is reduced to 800°C, and the rest is the same. The specific preparation steps are as follows:

[0073] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 150° C., and the reaction time is 16 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0074] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 8.5, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0075] (3) The zirconium hydroxide precursor is calcined at 800° C. for 3 hours in an air environment to obtain the zirconium oxide powder.

[0076] Comparative Example 3

[0077] A method for preparing zirconium oxide powder, compared with Example 1, the temperature of the hydrothermal reaction in step (1) is reduced to 130°C, and the rest is the same. The specific preparation steps are as follows:

[0078] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 100 mL reactor for hydrothermal reaction, the reactor filling degree is 80%, the reaction temperature is 130° C., and the reaction time is 16 h; after the reaction is completed, cool to room temperature and let stand for precipitation for 1 h.

[0079] (2) After the static precipitation in step (1), analytically pure ammonia water (concentration of 28 wt%) is added to the reaction solution for ammonolysis reaction. When the pH of the obtained mixed solution is 8.5, the obtained solution is allowed to stand for 0.75 h, and then the upper clear liquid is removed. The obtained precipitation slurry is washed with pure water several times and then dried to obtain a zirconium hydroxide precursor.

[0080] (3) The zirconium hydroxide precursor is calcined at 900° C. for 3 hours in an air environment to obtain the zirconium oxide powder.

[0081] Comparative Example 4

[0082] A method for preparing zirconium oxide powder, compared with Example 1, directly adopts a one-step hydrothermal ammonolysis reaction. The specific preparation steps are as follows:

[0083] (1) Weigh 18 g of raw material zirconium oxychloride octahydrate, measure 72 mL of water, and completely dissolve the zirconium oxychloride octahydrate in water to obtain a zirconium oxychloride aqueous solution; place the zirconium oxychloride aqueous solution in a 150 mL reactor for hydrothermal reaction, add analytical pure ammonia water (concentration of 28 wt%) during the hydrothermal reaction to adjust the pH of the mixed solution to 8.5, the filling degree of the reactor is 80%, the reaction temperature is 150°C, and the reaction time is 16 hours; after the reaction is completed, cool to room temperature and stand for precipitation for 1 hour. Then remove the supernatant, wash the obtained precipitation slurry with pure water several times and then dry to obtain a zirconium hydroxide precursor.

[0084] (2) The zirconium hydroxide precursor is calcined at 900° C. for 3 hours in an air environment to obtain the zirconium oxide powder.

[0085] The particle size and Cl of the zirconium oxide powder obtained in the above examples and comparative examples - The content was tested, and the results are shown in Table 1 below:

[0086] Table 1 Test results of zirconium oxide powder

[0087]

[0088]

[0089] By comparing the results of Example 1 with those of the embodiment, it can be seen that the pH of the ammonolysis reaction below 8 will result in a significant increase in the particle size of the product and Cl - The reason may be that too low pH will cause incomplete ammonolysis reaction and easily cause gelation reaction of zirconium oxychloride, which will eventually lead to the increase of product particle size and Cl - By comparing the results of Example 2 with those of the embodiment, it can be seen that the low calcination temperature of the precursor will lead to a decrease in the particle size of the product. - The content of the product did not increase significantly, but it still exceeded the application range of lithium battery positive electrode material additives. This shows that the appropriate calcination temperature of the present invention makes it easier to prepare powders with moderate particle size and is more conducive to the decomposition and removal of impurities. By comparing the results of Example 3 with the embodiment, it can be seen that the hydrothermal reaction temperature is too low, which will lead to a significant increase in the product particle size and Cl - The reason may be that the low temperature of the hydrothermal reaction will reduce the nucleation rate, giving the precursor particles more time to grow, which will increase the size of the precursor particles and increase the entrainment and encapsulation of chloride ions by the precipitate, ultimately resulting in a decrease in the product particle size and Cl - By comparing the results of Example 4 with those of the embodiment, it can be seen that the one-step hydrothermal ammonolysis reaction will result in a larger product particle size. -The content has not increased significantly, but it still exceeds the application range of lithium battery positive electrode material additives. The present invention first precipitates most of the zirconium ions through a hydrothermal reaction, and then precipitates the remaining zirconium ions through an ammonolysis reaction, which can control the precipitation rate to make the precipitate particles fine, and reduce the entrainment and wrapping of chloride ions by the precipitate, thereby reducing the particle size and chloride ion content of the final zirconium oxide nanopowder product, and improving the product quality.

[0090] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing monoclinic zirconium oxide nanopowder, characterized in that: The method comprises the following preparation steps: (1) adding zirconium oxychloride octahydrate into water to dissolve it to obtain a zirconium oxychloride aqueous solution, which is then placed in a hydrothermal reaction kettle and heated to 140 to 160° C. for hydrothermal reaction. After the reaction is completed, the solution is cooled to room temperature and allowed to stand for precipitation; (2) adding aqueous ammonia to the reaction solution of step (1) to carry out an ammonolysis reaction, allowing the solution to stand for aging to completely precipitate the remaining zirconium ions, separating the precipitate, washing it, and drying it to obtain a zirconium hydroxide precursor; (3) The zirconium hydroxide precursor obtained in step (2) is subjected to calcination treatment at 850-950° C. in an air environment to obtain the monoclinic zirconium oxide nanopowder.

2. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The mass ratio of zirconium oxychloride octahydrate to water added in step (1) is 1:3-5.

3. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: During the hydrothermal reaction process in step (1), the filling degree of the hydrothermal reaction kettle is 70-85%.

4. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The time of the hydrothermal reaction in step (1) is 12 to 16 hours; the time of the static precipitation is 0.5 to 1 hour.

5. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The mass concentration of the ammonia water in step (2) is 25-28%; the ammonia water is added to make the pH of the mixed solution 8-10.

6. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The standing aging time in step (2) is 0.5 to 1 hour.

7. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The washing in step (2) refers to washing with pure water multiple times.

8. The method for preparing a monoclinic zirconium oxide nanopowder according to claim 1, characterized in that: The time of the heat preservation calcination treatment in step (3) is 2 to 4 hours.

9. A monoclinic zirconium oxide nanopowder, characterized in that: The monoclinic zirconium oxide nanopowder is prepared by the method described in any one of claims 1 to 8; the D50 particle size of the monoclinic zirconium oxide nanopowder is less than 0.5 μm, Cl - Content <200ppm.

10. Use of the monoclinic zirconium oxide nanopowder according to claim 9 as an additive for positive electrode materials of lithium batteries.

Images