Preparation method of high-purity lithium oxide

Abstract

The present application relates to lithium material preparation technical field, provide a kind of preparation method of high-purity lithium oxide, comprising the following steps: after heating lithium hydroxide solution, slowly drop the mixed solution of low concentration hydrogen peroxide and dehydrating agent, after reaction centrifugation, obtain peroxide and mother liquor;Under low temperature conditions, peroxide is washed several times with detergent, obtain slurry and filtrate, slurry is obtained after magnetic removal Pure crystalline water peroxide;Under low temperature conditions, the obtained crystalline water peroxide is concentrated under reduced pressure, then vacuum drying is removed crystalline water, obtain dry product peroxide;Then pyrolysis is carried out under vacuum condition, inert gas is continuously introduced during pyrolysis process, obtain high-purity lithium oxide;The present application uses lithium hydroxide solution as lithium source, after treatment by adding low concentration hydrogen peroxide, high-purity lithium oxide can be prepared, so that the obtained lithium hydroxide solution of enterprise production line is effectively utilized, and resource waste and environmental pollution are not caused.

Description

Technical Field

[0001] This invention relates to the field of lithium material preparation technology, and more specifically, to a method for preparing high-purity lithium oxide. Background Technology

[0002] Lithium oxide (Li₂O) is an important inorganic compound with technological applications spanning materials science, the nuclear industry, and the energy sector. As an additive in the ceramics and glass industries, it significantly lowers the melting point of materials and improves thermal expansion properties and mechanical strength. Furthermore, it is a potential core electrolyte material and cathode material additive in solid-state lithium batteries, aiming to enhance battery energy density and safety. In the optics field, high-purity lithium oxide can be used in specialty optical glass. Therefore, lithium oxide has significant market demand and substantial development value.

[0003] Currently, there are four main methods for preparing lithium oxide: (1) lithium metal reacts with oxygen to directly generate lithium oxide. For example, Chinese patent CN102515211A discloses a method for preparing high-purity lithium oxide, in which lithium metal is placed in a furnace and oxygen is introduced for combustion to obtain lithium oxide. This process is simple and easy to operate, but the yield in industrialization is very low, the cost is high, and the activity of lithium metal is strong and the stability is poor, which poses a safety hazard; (2) lithium carbonate decomposes at high temperature to generate lithium oxide and carbon dioxide. This method has extremely high energy consumption, poor economic benefits, and the purity of the obtained product is low; (3) lithium hydroxide decomposes at high temperature. The process involves the decomposition of lithium hydroxide into lithium oxide and water. However, the equipment used in this method is prone to corrosion, has high energy consumption, and the byproducts are difficult to remove. (4) Hydrogen peroxide oxidizes lithium hydroxide to generate lithium peroxide, which is then pyrolyzed under vacuum to obtain lithium oxide. For example, Chinese Patent No. CN105271316A discloses a method for preparing high-purity lithium oxide using anhydrous lithium hydroxide. This method involves reacting 95%~99% high-concentration hydrogen peroxide distilled under reduced pressure with high-quality anhydrous lithium hydroxide under vacuum conditions. After preliminary oxidation, deep oxidation, thermal decomposition, and grinding, high-purity lithium oxide is obtained. This method has high requirements for the quality of raw materials and equipment, and it is easy to introduce lithium carbonate impurities. In addition, Chinese Patent No. CN120172430A discloses a production process for high-purity lithium oxide. This method involves mixing high-purity lithium hydroxide fine powder with hydrogen peroxide of 90%~99% mass concentration, performing a slow oxidation reaction, and separating solid and liquid components. Then, the lithium peroxide is directly pyrolyzed to obtain high-purity lithium oxide. This process still introduces lithium carbonate impurities and has high production costs, making it difficult to apply to large-scale production in enterprises. Summary of the Invention

[0004] The inventors unexpectedly discovered that treating the primary or secondary evaporation solution of lithium hydroxide in the enterprise workshop yields a good lithium source. Therefore, this invention uses lithium hydroxide solution as the lithium source and can produce high-purity lithium oxide by adding low-concentration hydrogen peroxide. This allows for the effective utilization of the lithium hydroxide solution obtained from the enterprise's production line, avoiding resource waste and environmental pollution, reducing enterprise production costs, and, more importantly, pioneering a new method for preparing high-purity lithium oxide more efficiently using liquid lithium hydroxide as the lithium source in combination with low-concentration hydrogen peroxide.

[0005] More specifically, the embodiments of the present invention are implemented through the following technical solutions: A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: After heating the lithium hydroxide solution, a mixture of 20-50% hydrogen peroxide and a dehydrating agent is slowly added dropwise while stirring continuously. After the reaction, the mixture is centrifuged to obtain lithium peroxide. S2. Washing: Under low temperature conditions, lithium peroxide is washed several times with detergent. The resulting slurry is demagnetized to obtain pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water is concentrated under reduced pressure at low temperature, and then vacuum dried to remove the water of crystallization, so as to obtain dry lithium peroxide; S4. Thermal decomposition: Then, pyrolysis is carried out under vacuum conditions, with inert gas continuously introduced during the pyrolysis process to obtain high-purity lithium oxide.

[0006] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: 1. This invention innovatively selects a primary heavy solution or a secondary evaporated lithium hydroxide solution from the workshop as the lithium source, avoiding the problem of introducing lithium carbonate impurities by directly using solid anhydrous lithium hydroxide micropowder as the lithium source in the traditional production process. Most importantly, the lithium hydroxide solution and hydrogen peroxide undergo a liquid-liquid homogeneous reaction under aqueous conditions. The reaction conditions are mild and controllable, and the generated lithium peroxide is homogeneously dissolved in water. There are no agglomeration or encapsulation problems during the reaction. Then, based on the different solubility characteristics of materials in ethanol (lithium peroxide is insoluble, lithium hydroxide is slightly soluble), adding ethanol during the reaction can precipitate lithium peroxide and remove a small amount of unreacted lithium hydroxide, thereby improving the yield and purity of the lithium peroxide product. This allows for the preparation of lithium oxide using a lower purity lithium hydroxide solution as raw material while removing impurities, and high-purity lithium oxide can be obtained.

[0007] 2. The preparation process of this invention does not require pretreatment of raw materials and can effectively utilize the lithium hydroxide solution obtained from the enterprise's production line, without causing resource waste and environmental pollution. It has low equipment requirements, relatively mild reaction conditions, and does not require additional impurity removal processes. It can stably prepare lithium oxide with a purity of ≥98.5% within 9 hours, which is more economical and feasible, and suitable for large-scale production by enterprises. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 The image shows the XRD pattern of lithium oxide obtained in Example 1 of this invention. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0011] The following is a detailed description of a method for preparing high-purity lithium oxide provided by an embodiment of the present invention.

[0012] A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: The lithium hydroxide solution is heated to 60℃~90℃ with continuous stirring. A mixture of 20~50% hydrogen peroxide and a dehydrating agent is slowly added dropwise while stirring continuously. After reacting for 1~2 hours, the mixture is centrifuged to obtain lithium peroxide. This step is carried out entirely in the liquid phase, and the system is a liquid-liquid homogeneous reaction system. Li + OH - Hydrogen peroxide molecules are completely dispersed in the aqueous solution, and the system has no concentration gradient or local overheating, which allows lithium peroxide to dissolve uniformly in the form of hydrated molecules without precipitation, encapsulation, or impurity adsorption problems.

[0013] S2. Washing: Lithium peroxide is washed several times with detergent at a low temperature of 10℃~20℃. The solid-liquid ratio of detergent to lithium peroxide is 1g:3~5ml. Impurities such as residual lithium hydroxide are removed to obtain slurry and filtrate. The slurry is demagnetized to obtain pure lithium peroxide with crystal water.

[0014] S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water is concentrated under reduced pressure at a low temperature of 30~50℃ and a vacuum degree of -0.08~-0.1MPa. Then, it is dried at a vacuum degree of -0.05~-0.09MPa and 100~150℃ for 1~6h. Preferably, it is dried at 120~150℃ for 1.5~2.5h to remove the water of crystallization and ethanol, so as to obtain dry lithium peroxide (purity ≥99%). The low concentration hydrogen peroxide system has moderate water activity, and the selection of lithium peroxide crystallization is extremely high, while impurities remain in the mother liquor. The crystallization purity is much higher than that of the existing solid-liquid process.

[0015] S4. Thermal decomposition: Then, thermal decomposition is carried out at a vacuum of 0 to -0.09 MPa and a temperature of 350 to 700 °C for 1 to 4 hours, with inert gas continuously introduced during the pyrolysis process to obtain high-purity lithium oxide. Preferably, thermal decomposition is carried out at a vacuum of -0.05 to -0.09 MPa and a temperature of 500 to 600 °C for 1.5 to 2.5 hours. This invention innovatively selects either a primary heavy solution or a secondary evaporated lithium hydroxide solution from the workshop as the lithium source, avoiding the problem of introducing lithium carbonate impurities that occurs when using solid anhydrous lithium hydroxide powder directly as the lithium source in traditional production processes. Most importantly, the lithium hydroxide solution and hydrogen peroxide undergo a liquid-liquid homogeneous reaction under aqueous conditions, which are mild and controllable. The generated lithium peroxide is homogeneously dissolved in water. Then, based on the different solubility characteristics of materials in ethanol (lithium peroxide is insoluble, lithium hydroxide is slightly soluble), adding ethanol during the reaction can precipitate lithium peroxide and simultaneously remove a small amount of unreacted lithium hydroxide, improving the yield and purity of the lithium peroxide product. This allows for the simultaneous removal of impurities while using a lower purity lithium hydroxide solution as a raw material to prepare lithium oxide, resulting in high-purity lithium oxide. This invention differs from traditional solid-liquid heterogeneous reactions, where the extremely high hydrogen peroxide concentration on the lithium hydroxide solid surface can cause localized overheating, leading to hydrogen peroxide decomposition, oxidant loss, decreased yield, and oxygen bubbles encapsulating the solid, resulting in uneven reaction. Simultaneously, carbon dioxide is adsorbed on the solid surface, generating lithium carbonate impurities.

[0016] This invention utilizes the primary or secondary evaporation solution of lithium hydroxide obtained during the production process as a lithium source, and combines it with low-concentration hydrogen peroxide to produce high-purity lithium oxide. This allows for the effective utilization of the lithium hydroxide solution obtained from the enterprise's production line, avoiding resource waste and environmental pollution. The cost of the oxidant is also greatly reduced, thus lowering the overall production cost for the enterprise. More importantly, there are no agglomeration or encapsulation problems during the homogeneous reaction process, ensuring product stability and yield, and producing high-purity lithium oxide.

[0017] To further ensure the fineness of lithium oxide, step S4 is also included: fine grinding: the lithium oxide product obtained in S3 is ground to obtain fine lithium oxide powder; specifically, a ball mill or a vacuum ball mill can be used for ball milling. During ball milling: the ball-to-material ratio is controlled at 3~8:1, the ball size is 10mm:5mm:2mm=1:1:1, the ball milling time is 1~3h, and the ball milling speed is 350~450r / min. Then, the product is sieved to control the particle size of the product to D50≤20μm.

[0018] It may also include step S5. Distillation recovery: The mother liquor obtained after centrifugation in S1 and the filtrate obtained after washing in S2 are recovered by distillation to obtain ≥95% ethanol and waste liquid; after calcium and magnesium removal, the waste liquid can be recycled to lithium hydroxide solution as a lithium source.

[0019] Further, in S1, the dehydrating agent is ethanol or methyl ethyl carbonate, preferably ethanol; the detergent is an alcohol solvent, such as methanol, ethanol, propanol, etc., preferably ethanol.

[0020] Furthermore, in S1, hydrogen peroxide is added in excess at a rate of 1% to 20%, with ethanol added in equal volumes. If too much hydrogen peroxide is added, byproducts will be generated, such as a complex of lithium peroxide crystal water and hydrogen peroxide, which will significantly affect the yield and purity of the final product. Therefore, it is preferable to add hydrogen peroxide at a molar ratio of H2O2 / LiOH·H2O of 0.55 to 0.6.

[0021] Furthermore, when introducing the inert gas, the gas flow rate should be controlled at 500-600 mL / min. Alternatively, the inert gas can be introduced using a gradient flow rate increase method. Specifically, the inert gas flow rate is gradually increased from 30-50 mL / min until it reaches 500-600 mL / min. Helium or argon can be used as the inert gas.

[0022] Raw material description The lithium hydroxide solution used in each embodiment of this application is all from the secondary evaporation solution of lithium hydroxide in our company's workshop, and its composition is shown in Table 1.

[0023] Table 1 - Ion content in lithium hydroxide solution

[0024] Example 1 A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: Heat a 140 g / L lithium hydroxide solution to 80 °C, add a 30% hydrogen peroxide and ethanol mixed solution, wherein the molar ratio of H2O2 / LiOH·H2O is 0.6:1, and ethanol and hydrogen peroxide are added in equal volumes, stir continuously for 2 h, and centrifuge to obtain lithium peroxide and mother liquor. S2. Washing: At 15℃, ethanol was added to the obtained lithium peroxide and washed and stirred for 30 min. The solid-liquid ratio of ethanol to lithium peroxide was 1 g: 4 ml. The washing was repeated twice to obtain slurry and filtrate. The slurry obtained from each washing was demagnetized by a magnetic rod to obtain pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water was concentrated under reduced pressure at 40℃ and vacuum degree -0.09MPa, and then dried at vacuum degree -0.09Mpa and 130℃ for 2h to obtain dry lithium peroxide; S4. Thermal decomposition: Dry lithium peroxide was thermally decomposed at 550℃ and -0.09 MPa for 2 hours. Helium gas was continuously introduced during the pyrolysis process, and the helium flow rate was controlled at 500 ml / min to obtain high-purity lithium oxide. S5. Fine grinding: Ball milling was performed using a vacuum ball mill jar. The ball milling parameters were: ball-to-material ratio 5:1, ball size 10mm:5mm:2mm = 1:1:1, ball milling time 2h, ball milling speed 400r / min, to obtain micronized lithium oxide. S6. Distillation and recovery: The mother liquor and filtrate obtained from S1 are purified by distillation to obtain 98% ethanol and waste liquid; after removing calcium and magnesium from the waste liquid, it is recycled to lithium hydroxide solution.

[0025] Phase analysis: The phase characterization of the lithium oxide product was performed by X-ray diffraction (XRD), and the results are shown in the figure. Figure 2 ,Depend on Figure 2 The product can be confirmed to be pure Li2O, without impurities such as LiOH and Li2CO3.

[0026] Example 2 A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: Heat a 143 g / L lithium hydroxide solution to 75 °C, add a 35% hydrogen peroxide and ethanol mixed solution, wherein the molar ratio of H2O2 / LiOH·H2O is 0.56:1, and ethanol and hydrogen peroxide are added in equal volumes, stir continuously for 2 h, and centrifuge to obtain lithium peroxide and mother liquor. S2. Washing: At 18°C, ethanol was added to the obtained lithium peroxide and washed and stirred for 40 min. The solid-liquid ratio of ethanol to lithium peroxide was 1 g: 4.2 ml. This was repeated 3 times to obtain slurry and filtrate. The slurry obtained from each washing was demagnetized by a magnetic rod to obtain pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water was concentrated under reduced pressure at 43℃ and vacuum degree -0.086MPa, and then dried at vacuum degree -0.07MPa and 120℃ for 2.5h to obtain dry lithium peroxide; S4. Thermal decomposition: Dry lithium peroxide was thermally decomposed at 560℃ and -0.08 MPa for 2 hours. Helium gas was continuously introduced during the pyrolysis process, and the helium flow rate was controlled at 550 ml / min to obtain high-purity lithium oxide. S5. Fine grinding: Ball milling was performed using a vacuum ball mill jar. The ball milling parameters were: ball-to-material ratio 6:1, ball size 10mm:5mm:2mm = 1:1:1, ball milling time 2h, ball milling speed 400r / min, to obtain micronized lithium oxide. S6. Distillation and recovery: The mother liquor and filtrate obtained from S1 are purified by distillation to obtain 97% ethanol and waste liquid; after removing calcium and magnesium from the waste liquid, it is recycled to lithium hydroxide solution.

[0027] Example 3 A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: Heat a 141 g / L lithium hydroxide solution to 66 °C, add a 35% hydrogen peroxide and ethanol mixed solution, wherein the molar ratio of H2O2 / LiOH·H2O is 0.58:1, and ethanol and hydrogen peroxide are added in equal volumes, stir continuously for 2 h, and centrifuge to obtain lithium peroxide and mother liquor. S2. Washing: At 14℃, ethanol was added to the obtained lithium peroxide and washed and stirred for 30 min. The solid-liquid ratio of ethanol to lithium peroxide was 1 g: 3 ml. The washing was repeated twice to obtain slurry and filtrate. The slurry obtained from each washing was demagnetized by a magnetic rod to obtain pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water was concentrated under reduced pressure at 36℃ and vacuum degree -0.088MPa, and then dried at vacuum degree -0.065Mpa and 125℃ for 2h to obtain dry lithium peroxide; S4. Thermal decomposition: Dry lithium peroxide was thermally decomposed at 500℃ and -0.09 MPa for 2 hours. Helium gas was continuously introduced during the pyrolysis process, and the helium flow rate was controlled at 500 ml / min to obtain high-purity lithium oxide. S5. Fine grinding: Ball milling was performed using a vacuum ball mill jar. The ball milling parameters were: ball-to-material ratio 5:1, ball size 10mm:5mm:2mm = 1:1:1, ball milling time 2h, ball milling speed 400r / min, to obtain micronized lithium oxide. S6. Distillation and recovery: The mother liquor and filtrate obtained from S1 are purified by distillation to obtain ≥95% ethanol and waste liquid; after removing calcium and magnesium from the waste liquid, it is recycled to lithium hydroxide solution.

[0028] Example 4 A method for preparing high-purity lithium oxide includes the following steps: S1. Oxidation: Heat a 147 g / L lithium hydroxide solution to 70 °C, add a 40% hydrogen peroxide and ethanol mixed solution, wherein the molar ratio of H2O2 / LiOH·H2O is 0.55:1, and ethanol and hydrogen peroxide are added in equal volumes. Stir the reaction continuously for 2 h, and centrifuge to obtain lithium peroxide and mother liquor. S2. Washing: At 17°C, ethanol was added to the obtained lithium peroxide and washed and stirred for 30 min. The solid-liquid ratio of ethanol to lithium peroxide was 1 g: 4.3 ml. This was repeated 3 times to obtain slurry and filtrate. The slurry obtained from each washing was demagnetized by a magnetic rod to obtain pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water was concentrated under reduced pressure at 43℃ and vacuum degree -0.083MPa, and then dried at vacuum degree -0.055MPa and 150℃ for 2h to obtain dry lithium peroxide; S4. Thermal decomposition: Dry lithium peroxide was thermally decomposed at 580℃ and -0.082 MPa for 2 hours. Helium gas was continuously introduced during the pyrolysis process, and the helium flow rate was controlled at 500 ml / min to obtain high-purity lithium oxide. S5. Fine grinding: Ball milling was performed using a vacuum ball mill jar. The ball milling parameters were: ball-to-material ratio 5:1, ball size 10mm:5mm:2mm = 1:1:1, ball milling time 2h, ball milling speed 400r / min, to obtain micronized lithium oxide. S6. Distillation and recovery: The mother liquor and filtrate obtained from S1 are purified by distillation to obtain 96% ethanol and waste liquid; after removing calcium and magnesium from the waste liquid, it is recycled to lithium hydroxide solution.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that the oxidation reaction temperature is 25°C.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is that the molar ratio of H2O2 / LiOH·H2O is 1.1:1.

[0031] Comparative Example 3 The difference between this comparative example and Example 1 is that the pyrolysis temperature of the pyrolysis section is 450°C.

[0032] Experimental Example 1 The products obtained from each embodiment and comparative example were analyzed and tested, and their purity was determined by titration. The results are shown in Table 2. Table 2 - Detection results of products obtained from various examples and comparative examples

[0033] In summary, this invention utilizes lithium hydroxide solution obtained from secondary evaporation in the workshop as a lithium source, and combines it with low-concentration hydrogen peroxide to carry out a liquid-liquid homogeneous reaction under aqueous conditions. The reaction conditions are mild and controllable, and impurities are removed while preparing lithium oxide, resulting in lithium oxide with a purity greater than 98%. This allows for the effective utilization of the lithium hydroxide solution obtained from the enterprise's production line, and there are no agglomeration or encapsulation problems during the homogeneous reaction process, ensuring product stability and yield, and producing high-purity lithium oxide.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity lithium oxide, characterized in that: Includes the following steps: S1. Oxidation: After heating the lithium hydroxide solution, a mixture of 20-50% hydrogen peroxide and dehydrating agent is slowly added dropwise while stirring continuously. After the reaction, the mixture is centrifuged to obtain lithium peroxide and mother liquor. S2. Washing: Under low temperature conditions, lithium peroxide is washed several times with detergent to obtain slurry and filtrate. After demagnetization, the slurry yields pure lithium peroxide with crystal water. S3. Concentration, crystallization and drying: The obtained lithium peroxide with crystal water is concentrated under reduced pressure at low temperature, and then vacuum dried to remove the water of crystallization, so as to obtain dry lithium peroxide; S4. Thermal decomposition: Dry lithium peroxide is pyrolyzed, with inert gas continuously introduced during the pyrolysis process to obtain high-purity lithium oxide.

2. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S1, the hydrogen peroxide is added in excess at a rate of 1% to 20% according to the chemical reaction, and the dehydrating agent is used in equal volume to the hydrogen peroxide.

3. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S1, the dehydrating agent is ethanol or methyl ethyl carbonate; in S2, the detergent is an alcohol solvent.

4. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S3, the obtained lithium peroxide with crystal water was concentrated under reduced pressure at a low temperature of 30~50℃ and a vacuum degree of -0.08~-0.1MPa. Dry at a vacuum of -0.05 to -0.09 MPa and a temperature of 100 to 150°C for 1 to 6 hours.

5. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S4, thermal decomposition occurs at a vacuum of 0 to -0.09 MPa and a temperature of 350 to 700 °C for 1 to 4 hours.

6. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S4, when introducing inert gas, the gas flow rate is controlled at 500~600mL / min.

7. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, In S4, when the inert gas is introduced, the inert gas flow rate is controlled to gradually increase from 30 to 50 mL / min until the gas flow rate reaches 500 to 600 mL / min.

8. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, It also includes step S5. Fine grinding: The lithium oxide product obtained in S4 is ground to obtain fine lithium oxide powder.

9. The method for preparing high-purity lithium oxide according to claim 1, characterized in that, It also includes step S6. Distillation recovery: The mother liquor obtained after centrifugation in S1 and the filtrate obtained after washing in S2 are recovered by distillation to obtain ≥95% ethanol and waste liquid; after impurity removal, the waste liquid can be recycled to lithium hydroxide solution as a lithium source.

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