Preparation method of low-cost high-purity lithium oxide

Abstract

The invention discloses a preparation method of low-cost high-purity lithium oxide. The method comprises the following steps: sequentially adding pure water and lithium hydroxide into a reaction kettle to prepare a reaction kettle base solution, then adding a hydrogen peroxide solution, carrying out peroxidation reaction, and strictly controlling the raw material adding sequence, the solid content of the reaction kettle base solution, the excess ratio of hydrogen peroxide, the flow rate of hydrogen peroxide, the reaction temperature and the reaction time; the method comprises the following steps: reacting hydrogen peroxide with lithium peroxide to obtain a solid-liquid mixture containing lithium peroxide, water and excessive unreacted hydrogen peroxide, carrying out dynamic vacuum drying on the solid-liquid mixture to obtain lithium peroxide, pyrolyzing the lithium peroxide, and finally grinding and screening the pyrolyzed product to obtain the high-purity lithium oxide. According to the method, conventional lithium hydroxide and commercially available hydrogen peroxide are adopted as raw materials, the raw material lithium hydroxide is completely reacted by strictly controlling the synthesis conditions of the intermediate product lithium peroxide, the high-purity lithium oxide can be obtained without solid-liquid separation, direct drying, pyrolysis, grinding and screening, and the method has the advantages of low cost, high production efficiency and high purity of the product lithium oxide.

Description

Technical Field

[0001] This invention relates to the field of lithium oxide technology, and in particular to a low-cost, high-purity lithium oxide preparation method. Background Technology

[0002] High-purity lithium oxide is a high-performance non-aqueous electrolyte and one of the important raw materials for synthesizing lithium-ion polymer electrolytes. It can also be used directly as a positive electrode material in lithium-ion batteries and is widely applied in lithium battery materials. As an additive, high-purity lithium oxide can improve the properties of glass, increasing its surface alkalinity, gloss, and strength.

[0003] There are four main methods for preparing lithium oxide: (1) Direct oxidation of metallic lithium to lithium oxide, such as the "A method for preparing high-purity lithium oxide" (CN102515211B) by Ganfeng Lithium Industry Co., Ltd., which oxidizes metallic lithium in a smelting furnace under vacuum and then grinds and sieves it to obtain lithium oxide. This method has low yield and high cost, and the presence of active metallic lithium can easily lead to safety hazards; (2) Lithium oxide is prepared by heating lithium carbonate at a high temperature of 700°C or above for 50 hours. This method has high energy consumption, low output per unit time and low labor productivity, poor economic benefits, and low purity of the obtained product; (3) Lithium oxide is prepared by lithium hydroxide pyrolysis. Although this method has low cost, it requires decomposition under high temperature and vacuum conditions, and the decomposition time is long and the temperature control is strict and difficult to control; (4) Lithium hydroxide reacts with hydrogen peroxide to generate lithium peroxide, and then the lithium peroxide is decomposed under vacuum conditions to obtain lithium oxide. Although this method has a long production process, the operating conditions are easy to control and the decomposition time is short, making it a relatively ideal method for preparing high-purity lithium oxide.

[0004] Currently, there are many reports in China on the preparation of lithium oxide using lithium hydroxide and hydrogen peroxide as raw materials. For example, Li Pengju et al.'s "Research on the Preparation Process of High-Purity Lithium Oxide" (Guangzhou Chemical Industry) added ethanol to lithium hydroxide monohydrate and hydrogen peroxide, mainly studying the effects of the molar ratio of the two raw materials, reaction temperature, ethanol ratio, and hydrogen peroxide volume ratio on lithium recovery rate, and obtained the optimal process conditions for synthesizing lithium peroxide; then, during the thermal decomposition of lithium peroxide, the effects of calcination temperature and calcination time on lithium conversion rate were analyzed, thus obtaining the optimal calcination conditions; finally, the optimal process conditions for synthesizing high-purity lithium oxide were obtained. Yang Chunfeng's "Research and Development of Lithium Oxide" (Xinjiang Nonferrous Metals) also added ethanol to lithium hydroxide monohydrate and hydrogen peroxide, mainly studying the effects of ethanol dosage on product solubility and agglomeration, and obtaining the optimal process conditions for synthesizing small particulate products. Ganfeng Lithium Industry Co., Ltd.'s "A Method for Preparing High-Purity Lithium Oxide Using Anhydrous Lithium Hydroxide" (CN105271316B) involves distilling hydrogen peroxide under reduced pressure to a mass concentration of 95%-99%, reacting it with anhydrous lithium hydroxide with a particle size D50 of 5-20 μm, and preparing high-purity lithium oxide through steps such as reduced pressure distillation, preliminary oxidation, deep oxidation, thermal decomposition, and grinding. Wuwei Dingge New Materials Co., Ltd.'s "A Production Process for High-Purity Lithium Oxide" (CN120172430A) involves mixing lithium hydroxide and hydrogen peroxide, performing a peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide, then separating the mixture to obtain a supernatant containing lithium hydroxide and a solid containing lithium peroxide. The supernatant containing lithium hydroxide is then dried to obtain recovered lithium hydroxide, and the solid containing lithium peroxide is thermally decomposed under an inert gas atmosphere to obtain high-purity lithium oxide powder.

[0005] As mentioned above, existing literature generally divides the methods for preparing lithium oxide using lithium hydroxide and hydrogen peroxide as raw materials into two types: (1) Adding ethanol: Ethanol is used as a dehydrating agent and cleaning agent to improve the yield and purity of lithium peroxide products. However, the use of ethanol increases costs and poses safety hazards, causing environmental pollution. (2) Not adding ethanol: Anhydrous lithium hydroxide and high-concentration hydrogen peroxide are required as raw materials. Carbon dioxide is easily introduced during the preparation of anhydrous lithium hydroxide, and there are certain requirements for particle size. Hydrogen peroxide needs to be distilled under reduced pressure first, which takes a long time and consumes a lot of energy. The whole process has certain limitations on equipment and raw materials. Alternatively, conventional battery-grade lithium hydroxide and commercially available hydrogen peroxide can be used as raw materials to prepare lithium oxide. However, there are problems such as incomplete reaction of lithium hydroxide, a small amount of lithium hydroxide still remaining in the solid after separation of the solid-liquid mixture, low purity of lithium oxide, and improper order of addition of raw materials lithium hydroxide and hydrogen peroxide. If hydrogen peroxide is added first and then lithium hydroxide is added, the exothermic reaction will intensify the decomposition of hydrogen peroxide, and the rapid generation of a large amount of gas will cause a sharp increase in the pressure of the reaction vessel, which is very dangerous. Summary of the Invention

[0006] The main technical problem solved by this invention is to overcome the problems of high cost, low production efficiency and low purity in the preparation of lithium oxide mentioned in the background art above, and to provide a simple, safe, low-cost, efficient and high-purity method for preparing lithium oxide.

[0007] This invention provides a low-cost, high-purity lithium oxide preparation method, comprising the following steps:

[0008] S1 Peroxidation reaction: First, pure water and lithium hydroxide are added to the reactor in sequence to prepare the bottom liquid of the reactor. Then, hydrogen peroxide solution is added, and the peroxidation reaction is carried out and aged to obtain a solid-liquid mixture containing lithium peroxide, water and excess unreacted hydrogen peroxide.

[0009] S2 Vacuum drying: The solid-liquid mixture obtained above is subjected to dynamic vacuum drying to obtain lithium peroxide; S3 Pyrolysis: The lithium peroxide obtained above is pyrolyzed to obtain bulk lithium oxide;

[0010] S4 Grinding and sieving: Grind and sieve the above-obtained blocky lithium oxide to obtain high-purity lithium oxide powder.

[0011] Furthermore, in step S1, the solid content of the bottom liquid of the reactor is controlled within the range of 65%-80%, and the solid content = mass of lithium hydroxide : mass of lithium hydroxide + mass of pure water.

[0012] Furthermore, in step S1, the C% of lithium hydroxide is less than 0.05%, wherein the lithium hydroxide is any one or both of lithium hydroxide monohydrate and anhydrous lithium hydroxide, preferably lithium hydroxide monohydrate, and the particle size D50 of lithium hydroxide is 5-400 μm, preferably 100-350 μm.

[0013] Furthermore, in step S1, the concentration of the hydrogen peroxide solution is controlled within the range of 25%-50%, the flow rate is controlled within the range of 6.5-15.0 g / L, and the molar ratio of the solute hydrogen peroxide to lithium hydroxide is controlled within the range of 0.6-0.8.

[0014] Furthermore, in step S1, the temperature control range of the reactor is 30-50℃, the rotation speed control range is 200-500rpm, the reaction time control range after adding hydrogen peroxide solution is 25-60min, the aging time control range is 20-60min, inert gas is introduced into the reactor, and the pressure control range inside the reactor is 0-10pa.

[0015] Furthermore, in step S2, the vacuum control range of the dynamic drying equipment is <-0.09 MPa, the drying temperature control range is 105-120℃, the drying time control range is >6h, the moisture content of the dried solid product is <200 ppm, and after drying, the material is discharged and sealed with inert gas.

[0016] Furthermore, in step S3, the pyrolysis temperature is controlled within the range of 380-600℃, the heating rate is controlled within the range of 1-5℃ / min, inert gas is introduced into the furnace, and the carbon dioxide content is controlled within the range of <10ppm.

[0017] Furthermore, in step S4, the grinding mill speed control range is 200-600 rpm, the grinding time control range is >2h, the grinding media includes polyurethane balls and zirconium balls, the mass ratio of polyurethane balls to zirconium balls is 1:2-10, and the total mass of the grinding media to the mass ratio of lithium oxide is 2-10:1.

[0018] Furthermore, the material turnover and grinding and sieving in steps S3 and S4 are carried out under environmental conditions with a carbon dioxide content of <10ppm and a dew point of <-15℃.

[0019] Furthermore, the high-purity lithium oxide prepared has a purity >98.5%, Li₂CO₃% <1.2%, and a particle size D50 of 5-15 μm.

[0020] Beneficial effects:

[0021] (1) The present invention uses conventional lithium hydroxide and commercially available hydrogen peroxide as raw materials to prepare lithium oxide. The raw materials are low in cost and readily available. Compared with the method of preparing lithium oxide using anhydrous lithium hydroxide and high-concentration hydrogen peroxide as raw materials, it does not require special raw material processing steps or complex step-by-step oxidation steps. It is easy to operate, facilitates continuous production, and has low energy consumption.

[0022] (2) By strictly controlling the synthesis conditions of the intermediate product lithium peroxide, the present invention enables the raw material lithium hydroxide to react completely. Compared with the conventional method that requires the preparation of lithium oxide with lithium hydroxide and high-concentration hydrogen peroxide and the intermediate solid-liquid separation to remove unreacted lithium hydroxide, the present invention does not require solid-liquid separation of unreacted lithium hydroxide and does not require the addition of ethanol. It has the advantages of short process flow, low cost, high production efficiency and high product purity. Attached Figure Description

[0023] Figure 1 XRD of hydrogen peroxide, the intermediate product prepared in Example 1 of this invention;

[0024] Figure 2 The XRD pattern of lithium oxide prepared in Example 1 of this invention;

[0025] Figure 3This is the XRD pattern of hydrogen peroxide, the intermediate product prepared in Comparative Example 2 of this invention.

[0026] Figure 4 This is the XRD pattern of lithium oxide prepared in Comparative Example 2 of this invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to embodiments and comparative examples.

[0028] Example 1

[0029] S1, Peroxidation reaction: First, add 660g of pure water and 2000g of lithium hydroxide monohydrate to the reactor sequentially. The particle size (D50) of the lithium hydroxide monohydrate is 300μm, and the C% is 0.03%. The solid content of the liquid at the bottom of the reactor is 75%. The temperature of the reactor is controlled at 40℃, the stirring speed is controlled at 250rpm, nitrogen gas is continuously introduced into the reactor, and the pressure inside the reactor is controlled at 5pa. Then, add 3890g of a 30% hydrogen peroxide solution. The molar ratio of hydrogen peroxide to lithium hydroxide monohydrate is 0.72, and the flow rate of the hydrogen peroxide solution is 8g / L. After reacting for 40min, age for 30min to obtain a mixture containing lithium peroxide, water, and excess hydrogen peroxide.

[0030] S2, Vacuum drying: The mixture obtained above is transferred into a drying device for dynamic drying. The vacuum degree of the drying device is -0.098Mpa, the drying temperature is 118℃, and after drying for 8 hours, the material is discharged and sealed with nitrogen gas to obtain lithium peroxide with a moisture content of 150ppm.

[0031] S3, Pyrolysis: The lithium peroxide obtained above is pyrolyzed. Nitrogen gas is continuously introduced into the pyrolysis furnace. The carbon dioxide content is 5 ppm at the start-up, the pyrolysis temperature is 410℃, and the heating rate is 3℃ / min to obtain blocky lithium oxide.

[0032] S4, Grinding and Sieving: The obtained blocky lithium oxide is ground and sieved to obtain high-purity lithium oxide powder. The grinding mill speed is controlled at 250 rpm, the grinding time is 3 hours, the mass ratio of polyurethane balls to zirconium balls in the grinding media is 1:4, and the mass ratio of the total mass of the grinding media to the mass of lithium oxide is 4:1. Grinding, loading, unloading, and sieving are all carried out in an environment with a carbon dioxide content of 5 ppm and a dew point of -20℃.

[0033] Example 2

[0034] S1, Peroxidation reaction: First, add 660g of pure water and 2000g of lithium hydroxide monohydrate to the reactor sequentially. The particle size (D50) of the lithium hydroxide monohydrate is 300μm, and the C% is 0.03%. The solid content of the liquid at the bottom of the reactor is 75%. The temperature of the reactor is controlled at 40℃, the stirring speed is controlled at 250rpm, nitrogen gas is continuously introduced into the reactor, and the pressure inside the reactor is controlled at 5pa. Then, add 4212g of a 30% hydrogen peroxide solution. The molar ratio of hydrogen peroxide to lithium hydroxide monohydrate is 0.78, and the flow rate of the hydrogen peroxide solution is 8g / L. After reacting for 40min, age for 30min to obtain a mixture containing lithium peroxide, water, and excess hydrogen peroxide.

[0035] S2, Vacuum drying: The mixture obtained above is transferred into a drying device for dynamic drying. The vacuum degree of the drying device is -0.098 MPa, the drying temperature is 118℃, and after drying for 8 hours, the material is discharged and sealed with nitrogen gas to obtain lithium peroxide with a moisture content of 150 ppm.

[0036] S3, Pyrolysis: The lithium peroxide obtained above is pyrolyzed. Nitrogen gas is continuously introduced into the pyrolysis furnace. The carbon dioxide content is 5 ppm at the start. The pyrolysis temperature is 410℃ and the heating rate is 3℃ / min to obtain blocky lithium oxide.

[0037] S4, Grinding and Sieving: The obtained blocky lithium oxide is ground and sieved to obtain high-purity lithium oxide powder. The grinding mill speed is controlled at 250 rpm, the grinding time is 3 hours, the mass ratio of polyurethane balls to zirconium balls in the grinding media is 1:4, and the mass ratio of the total mass of the grinding media to the mass of lithium oxide is 4:1. Grinding, loading, unloading, and sieving are all carried out in an environment with a carbon dioxide content of 5 ppm and a dew point of -20℃.

[0038] Comparative Example 1

[0039] Compared with Example 1, the amount of pure water added to the reaction in step S1 is 360g, the liquid-solid content at the bottom of the reaction vessel is 85%, and the other operations are the same as in Example 1.

[0040] Comparative Example 2

[0041] Compared with Example 1, the amount of pure water added to the reaction in step S1 is 1330g, the liquid-to-solid content at the bottom of the reaction vessel is 60%, and the other operations are the same as in Example 1.

[0042] Comparative Example 3

[0043] Compared with Example 1, the weight of the 30% hydrogen peroxide aqueous solution added to the reaction in step S1 is 2972g, the molar ratio of the solute hydrogen peroxide to lithium hydroxide monohydrate is 0.65, and the other operations are the same as in Example 1.

[0044] Comparative Example 4

[0045] Compared with Example 1, the weight of the 30% hydrogen peroxide aqueous solution added to the reaction in step S1 is 4593g, the molar ratio of the solute hydrogen peroxide to lithium hydroxide monohydrate is 0.85, and the other operations are the same as in Example 1.

[0046] Comparative Example 5

[0047] Compared with Example 1, in step S1, 5836g of 20% hydrogen peroxide solution was added to the reaction, the molar ratio of hydrogen peroxide to lithium hydroxide monohydrate was 0.72, and the other operations were the same as in Example 1.

[0048] Comparative Example 6

[0049] Compared with Example 1, in step S1, 1945g of 60% hydrogen peroxide solution was added to the reaction, the molar ratio of hydrogen peroxide to lithium hydroxide monohydrate was 0.72, and the other operations were the same as in Example 1.

[0050] Comparative Example 7

[0051] Compared with Example 1, the flow rate of hydrogen peroxide solution in step S1 is 5 g / L, and the other operations are the same as in Example 1.

[0052] Comparative Example 8

[0053] Compared with Example 1, the flow rate of hydrogen peroxide solution in step S1 is 18 g / L, and the other operations are the same as in Example 1.

[0054] Comparative Example 9

[0055] Compared with Example 1, the temperature of the reactor in step S1 is controlled at 25°C, and the other operations are the same as in Example 1.

[0056] Comparative Example 10

[0057] Compared with Example 1, the temperature of the reactor in step S1 is controlled at 60°C, and the other operations are the same as in Example 1.

[0058] Comparative Example 11

[0059] Compared with Example 1, the reaction time of the reactor after adding hydrogen peroxide in step S1 is 15 minutes, and the other operations are the same as in Example 1.

[0060] Comparative Example 12

[0061] Compared with Example 1, the reaction time of the reactor after adding hydrogen peroxide in step S1 is 90 minutes, and the other operations are the same as in Example 1.

[0062] The XRD, purity (Li2O%), and Li2CO3%) of the obtained low-cost, high-purity lithium oxide were evaluated using the following methods.

[0063] (1) XRD

[0064] Place the powder sample in the sample holder and compact it. Then place it on the sample holder of the XRD diffractometer and close the instrument door. Set the scanning range to 15°-75° and the scanning speed to 15° / min, and start the test.

[0065] (2) Purity: Li2O%, Li2CO3%

[0066] Preparation of sample solution: Place a 100mL dry beaker on an analytical balance and weigh 0.1500g ± 0.0005g of lithium oxide sample (recorded as m). Add a small amount of deoxygenated water along the beaker wall to wet the material and quickly transfer it to a 250mL Erlenmeyer flask. Add 2 drops of phenolphthalein indicator to the Erlenmeyer flask and titrate with hydrochloric acid standard solution until the red color completely disappears, reaching the endpoint of the first titration step. Record the volume of hydrochloric acid standard solution consumed, V1. Then add 5 drops of methyl red indicator to the Erlenmeyer flask and continue titrating with hydrochloric acid standard solution until the solution changes from yellow to bright red, reaching the endpoint of the second titration step. Record the volume of hydrochloric acid standard solution consumed at this point, V2.

[0067] The contents of Li₂O and Li₂CO₃, expressed as mass percentages, are calculated using the following formula:

[0068]

[0069] In the formula:

[0070] V1---The volume of hydrochloric acid standard solution consumed in the first titration step, in mL;

[0071] V2---The total volume of hydrochloric acid standard solution consumed in the two-step titration, in mL;

[0072] m --- Sample mass, in grams;

[0073] C HCL ---Molar concentration of standard hydrochloric acid solution, in mol / L.

[0074] Table 1 Comparison data between the examples and comparative examples

[0075]

[0076] evaluate

[0077] From the appendix Figure 1 Appendix Figure 2As can be seen from Table 1, the lithium oxide prepared in Example 1 is basically free of impurity phases and has high purity. The intermediate product lithium peroxide is also basically free of impurity phases, indicating that the raw material lithium hydroxide has basically reacted completely.

[0078] From the appendix Figure 3 Appendix Figure 4 As shown in Table 1, compared with Example 1, the lithium oxide prepared in Comparative Example 2 clearly contains impurity lithium hydroxide, resulting in low purity. The intermediate product, lithium peroxide, also clearly contains impurity lithium hydroxide. Compared with Example 1, Comparative Example 2 has a lower solid content and a higher water content in the reaction system. This leads to partial dissolution of the intermediate product, lithium peroxide, to form lithium hydroxide, which remains after subsequent sintering. The low purity of the lithium oxide prepared in Comparative Example 1 is due to its higher solid content, insufficient water content in the reaction system, inadequate contact with the raw materials, and incomplete reaction of some lithium hydroxide. Therefore, the solid content of the bottom liquid in step S1 needs to be controlled within a certain range of 65%-80%. A high solid content will lead to insufficient reaction of the raw material lithium hydroxide, while a low solid content will result in partial dissolution of the intermediate product, lithium peroxide, to form lithium hydroxide, which remains after subsequent sintering. Both of these factors contribute to a low purity of the final lithium oxide product.

[0079] As shown in Table 1, the lithium oxide prepared in Comparative Example 3 has a lower purity compared to Example 1. This is because the amount of hydrogen peroxide in Comparative Example 3 is too small. Hydrogen peroxide itself is easily decomposed by heat, and its reaction with lithium hydroxide is exothermic, causing the added hydrogen peroxide to decompose. This results in less hydrogen peroxide actually reacting with the raw material, lithium hydroxide monohydrate, leading to incomplete reaction. The lithium oxide prepared in Comparative Example 4 has a purity very close to that of Examples 1 and 2, but the amount of hydrogen peroxide in Comparative Example 4 is significantly excessive. Therefore, the molar ratio of hydrogen peroxide to lithium hydroxide needs to be controlled within a certain range of 0.6-0.8. Insufficient hydrogen peroxide will result in incomplete peroxidation of the raw material, lithium hydroxide monohydrate, leading to incomplete reaction, while excessive hydrogen peroxide will result in waste.

[0080] As shown in Table 1, compared with Example 1, the lithium oxide prepared in Comparative Examples 5 and 6 had lower purity. This is because the hydrogen peroxide concentration in Comparative Example 5 was too low, resulting in more water being added, causing partial dissolution of the generated lithium peroxide and thus low purity of the final product. Conversely, the hydrogen peroxide concentration in Comparative Example 6 was too high, resulting in less water being added, insufficient material contact, and incomplete reaction of the raw material lithium hydroxide, also leading to low purity of the final product. Therefore, the hydrogen peroxide concentration needs to be controlled within a certain range of 25%-50%. If the hydrogen peroxide concentration is too low, partial dissolution of the generated lithium peroxide occurs; if the hydrogen peroxide concentration is too high, incomplete reaction of lithium hydroxide occurs, resulting in low purity of the final product.

[0081] As shown in Table 1, compared with Example 1, the lithium oxide prepared in Comparative Examples 7 and 8 had lower purity. This is because the hydrogen peroxide flow rate in Comparative Example 7 was too slow, causing the heat generated by the reaction to decompose the hydrogen peroxide. The hydrogen peroxide was added for too long, resulting in partial decomposition and insufficient hydrogen peroxide reacting with the lithium hydroxide raw material, leading to incomplete reaction. Similarly, the hydrogen peroxide flow rate in Comparative Example 8 was too fast, causing a rapid increase in heat and drastic decomposition of the hydrogen peroxide, resulting in insufficient hydrogen peroxide reacting with the lithium hydroxide raw material, also leading to incomplete reaction. Therefore, the flow rate of hydrogen peroxide needs to be controlled within a certain range of 6.5-15.0 g / L; a flow rate that is too slow or too fast will result in incomplete reaction.

[0082] As shown in Table 1, compared with Example 1, the lithium oxide prepared in Comparative Examples 9 and 10 had lower purity. This is because the reaction temperature in Comparative Example 9 was too low, which was not conducive to the reaction; the reaction temperature in Comparative Example 10 was too high, which promoted the decomposition of hydrogen peroxide, resulting in less hydrogen peroxide reacting with the raw material lithium hydroxide and incomplete reaction. Therefore, the reaction temperature needs to be controlled within a certain range of 30-50℃. Too low a reaction temperature is not conducive to the reaction, while too high a reaction temperature leads to the decomposition of hydrogen peroxide and incomplete reaction.

[0083] As shown in Table 1, compared with Example 1, the lithium oxide prepared in Comparative Examples 11 and 12 had lower purity. This is because the reaction time in Comparative Example 11 was too short, and the raw materials lithium hydroxide monohydrate and hydrogen peroxide did not react completely; the reaction time in Comparative Example 12 was too long, and the product lithium peroxide partially dissolved. Therefore, the reaction temperature needs to be controlled within a certain range of 25-60 min. If the reaction time is too short, the raw materials lithium hydroxide monohydrate and hydrogen peroxide will not react completely; if the reaction time is too long, the product lithium peroxide partially dissolves.

[0084] It should be noted that the descriptions of these embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. The above are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A low-cost, high-purity lithium oxide preparation method, characterized in that, Includes the following steps: S1 Peroxidation reaction: First, pure water and lithium hydroxide are added to the reactor in sequence to prepare the bottom liquid of the reactor. Then, hydrogen peroxide solution is added, and the peroxidation reaction is carried out and aged to obtain a solid-liquid mixture containing lithium peroxide, water and excess unreacted hydrogen peroxide. S2 Vacuum drying: The solid-liquid mixture obtained above is subjected to dynamic vacuum drying to obtain lithium peroxide; S3 Pyrolysis: The lithium peroxide obtained above is pyrolyzed to obtain bulk lithium oxide; S4 Grinding and sieving: Grind and sieve the above-obtained blocky lithium oxide to obtain high-purity lithium oxide powder.

2. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S1, the solid content of the bottom liquid of the reactor is controlled within the range of 65%-80%, and the solid content = mass of lithium hydroxide : mass of lithium hydroxide + mass of pure water.

3. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S1, the C% of lithium hydroxide is less than 0.05%, wherein the lithium hydroxide is any one or both of lithium hydroxide monohydrate and anhydrous lithium hydroxide, and the particle size D50 of lithium hydroxide is 5-400 μm.

4. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S1, the concentration of the hydrogen peroxide solution is controlled within the range of 25%-50%, the flow rate is controlled within the range of 6.5-15.0 g / L, and the molar ratio of the solute hydrogen peroxide to lithium hydroxide is controlled within the range of 0.6-0.

8.

5. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S1, the temperature of the reactor is controlled within the range of 30-50℃, the rotation speed is controlled within the range of 200-500rpm, the reaction time after adding hydrogen peroxide solution is controlled within the range of 25-60min, the aging time is controlled within the range of 20-60min, inert gas is introduced into the reactor, and the pressure inside the reactor is controlled within the range of 0-10pa.

6. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S2, the vacuum control range of the dynamic drying equipment is <-0.09 MPa, the drying temperature control range is 105-120℃, the drying time control range is >6h, the moisture content of the dried solid product is <200 ppm, and after drying, the material is discharged and sealed with inert gas.

7. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S3, the pyrolysis temperature is controlled within the range of 380-600℃, the heating rate is controlled within the range of 1-5℃ / min, inert gas is introduced into the furnace, and the carbon dioxide content is controlled within the range of <10ppm.

8. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, In step S4, the grinding mill speed control range is 200-600 rpm, the grinding time control range is >2h, the grinding media includes polyurethane balls and zirconium balls, the mass ratio of polyurethane balls to zirconium balls is 1:2-10, and the total mass of the grinding media to the mass ratio of lithium oxide is 2-10:

1.

9. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, The material turnover and grinding and sieving in steps S3 and S4 are carried out under environmental conditions with a carbon dioxide content of <10ppm and a dew point of <-15℃.

10. The method for preparing low-cost, high-purity lithium oxide as described in claim 1, characterized in that, The prepared high-purity lithium oxide has a purity >98.5%, Li₂CO₃% <1.2%, and a particle size D50 of 5-15 μm.

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