Production process of high-purity lithium oxide

Abstract

The invention discloses a production process of high-purity lithium oxide, and relates to the technical field of lithium oxide preparation. The production process of the high-purity lithium oxide comprises the following steps: mixing lithium hydroxide and hydrogen peroxide with the mass concentration of 90-99%, and carrying out peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide; carrying out solid-liquid separation on the mixture containing the lithium peroxide and the lithium hydroxide to obtain a supernatant containing the lithium hydroxide and a solid containing the lithium peroxide; and carrying out drying treatment on the supernatant containing the lithium hydroxide to obtain the recycled lithium hydroxide, and carrying out thermal decomposition on the solid containing lithium peroxide in an inert gas protective atmosphere to obtain the high-purity lithium oxide powder. According to the technical scheme, the high-purity lithium oxide is prepared by adopting a process of peroxidizing lithium hydroxide into lithium peroxide and then carrying out thermal decomposition, the powder can be obtained without grinding, and the method has the advantages of high production efficiency, low energy consumption and high raw material utilization rate.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium oxide preparation, and particularly to a production process of high-purity lithium oxide. Background Art

[0002] Lithium oxide (Li2O), as an important inorganic compound, has a wide range of applications in multiple high-tech fields. Especially in lithium-ion batteries, electronic materials, glass and ceramic manufacturing, and the nuclear industry, the demand for high-purity lithium oxide is increasing day by day.

[0003] The production processes of high-purity lithium oxide mainly include the following methods: (1) Thermal decomposition method of lithium carbonate: Lithium carbonate is thermally decomposed at high temperature to generate lithium oxide. This method has a high reaction temperature, large energy consumption, and the problem of residual carbonate in the product; (2) Solvent extraction method: Organic solvents are used to extract lithium ions from lithium-containing solutions, and then converted into lithium oxide through chemical precipitation or other methods. This method can effectively remove certain impurities, but the operation is complex, the cost is high, and new organic impurities are easily introduced; (3) Electrolysis method: Metal lithium is prepared by electrolyzing lithium chloride solution, and then metal lithium is oxidized to lithium oxide. Although this method can obtain a high purity, the process is complex, the energy consumption is high, and it has a greater impact on the environment; (4) Thermal decomposition method of lithium hydroxide: Lithium hydroxide is decomposed at a high temperature above 800 °C to generate lithium oxide. Since the melting point of lithium hydroxide is relatively low, it is extremely easy to form pellets on the surface during high-temperature sintering, but the core of the pellet is still lithium hydroxide and is not completely burned through and decomposed, resulting in low purity of lithium oxide. To improve the product purity, the lithium hydroxide in the center of the pellet needs to be completely decomposed, which requires a higher sintering temperature and extremely high energy consumption; (5) Thermal decomposition method of lithium peroxide: Lithium peroxide is generated by the reaction of lithium hydroxide and hydrogen peroxide, and lithium peroxide is thermally decomposed in a vacuum device to generate lithium oxide. This method has easy-to-control operating conditions, short reaction time, and high product quality, and is a relatively ideal method.

[0004] At present, there are already some preparation methods for preparing lithium oxide using lithium hydroxide and hydrogen peroxide as raw materials. However, these production processes for preparing lithium oxide using lithium hydroxide and hydrogen peroxide as raw materials are relatively complex, and high-purity lithium oxide powder products need to be prepared through steps such as preliminary oxidation, deep oxidation, thermal decomposition, and grinding, and the raw material utilization rate is low. Therefore, there is still a need to develop a production process that can prepare high-purity lithium oxide and has high production efficiency, high raw material utilization rate, and small product particle size. Summary of the Invention

[0005] The main object of the present invention is to propose a production process of high-purity lithium oxide, aiming to solve the problems of low production efficiency, low raw material utilization rate, and large product particle size existing in the existing high-purity lithium oxide production processes.

[0006] To achieve the above object, the present invention provides a production process of high-purity lithium oxide, comprising the following steps:

[0007] Mix lithium hydroxide with hydrogen peroxide having a mass concentration of 90% to 99% and carry out a peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide;

[0008] Perform solid-liquid separation on the mixture containing lithium peroxide and lithium hydroxide to obtain a supernatant containing lithium hydroxide and a solid containing lithium peroxide;

[0009] Perform drying treatment on the supernatant containing lithium hydroxide to obtain recycled lithium hydroxide; thermally decompose the solid containing lithium peroxide in an inert gas protection atmosphere to obtain high-purity lithium oxide powder.

[0010] In one embodiment, the mass ratio of the lithium hydroxide to the hydrogen peroxide is 1:(1.5 - 5).

[0011] In one embodiment, the thermal decomposition temperature is 600 - 800 °C; and / or,

[0012] The thermal decomposition time is 10 - 20 h.

[0013] In one embodiment, the temperature of the peroxidation reaction is 0 - 10 °C.

[0014] In one embodiment, the time of the peroxidation reaction is 10 - 36 h.

[0015] In one embodiment, in the step of mixing lithium hydroxide with hydrogen peroxide having a mass concentration of 90% to 99% and carrying out a peroxidation reaction, the particle size of the lithium hydroxide is 1 - 10 μm.

[0016] In one embodiment, in the step of mixing lithium hydroxide with hydrogen peroxide having a mass concentration of 90% to 99% and carrying out a peroxidation reaction, the purity of the lithium hydroxide is not less than 99.5%.

[0017] In one embodiment, in the step of performing drying treatment on the supernatant containing lithium hydroxide to obtain recycled lithium hydroxide, the drying treatment method includes evaporation using a high-efficiency evaporator.

[0018] In one embodiment, in the step of thermally decomposing the solid containing lithium peroxide in an inert gas protection atmosphere, the inert gas includes nitrogen.

[0019] The technical solution of the present invention provides a production process of high-purity lithium oxide. Using commercially available battery-grade (or high-purity grade) lithium hydroxide and commercially available hydrogen peroxide as raw materials, the raw material sources are convenient, and no special raw material processing procedures are required. The entire synthesis process is carried out under normal pressure, without the need for complex stepwise oxidation or stepwise thermal decomposition reactions. The operation is convenient, facilitating continuous production. The production process flow is simple, with low energy consumption, and the unreacted lithium hydroxide is recycled, resulting in high raw material utilization rate. In the high-purity lithium oxide production process provided by the present invention, first, lithium hydroxide and hydrogen peroxide are subjected to a peroxidation reaction to generate lithium peroxide. Since there is unreacted lithium hydroxide in the reaction system, a mixture containing lithium hydroxide and lithium peroxide will be obtained after the reaction. Subsequently, taking advantage of the characteristics that lithium hydroxide has a high solubility in water while lithium peroxide has a low solubility in water, the mixture containing lithium hydroxide and lithium peroxide is subjected to solid-liquid separation, enabling most of the lithium hydroxide to dissolve in water to form a supernatant, while lithium peroxide forms a solid precipitate, thereby obtaining a supernatant containing lithium hydroxide and a solid substance containing lithium peroxide. Among them, the solid substance containing lithium peroxide includes lithium peroxide and a part of lithium hydroxide that has not yet dissolved in water. Subsequently, the supernatant containing lithium hydroxide is dried to recycle the lithium hydroxide dissolved in water. The solid substance containing lithium peroxide is thermally decomposed under an inert gas protection atmosphere to thermally decompose lithium peroxide and lithium hydroxide to obtain high-purity lithium oxide powder. The high-purity lithium oxide production process provided by the present invention results in a powder product after thermal decomposition of the lithium oxide, without the need for pulverization, and the obtained product has a high purity. In addition, ethanol is avoided as a dehydrating agent and cleaning agent in the production process of the present invention, reducing production costs and reducing safety and environmental protection risks. Detailed Embodiments

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, such directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0022] In addition, if the embodiments of the present invention involve descriptions such as "first" and "second", the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] Lithium oxide (Li2O), as an important inorganic compound, has a wide range of applications in multiple high-tech fields. Especially in lithium-ion batteries, electronic materials, glass and ceramic manufacturing, and the nuclear industry, the demand for high-purity lithium oxide is increasing day by day.

[0024] The production processes of high-purity lithium oxide mainly include the following methods: (1) Thermal decomposition method of lithium carbonate: Lithium carbonate is thermally decomposed at high temperature to generate lithium oxide. This method has a high reaction temperature, problems of high energy consumption and residual carbonate in the product; (2) Solvent extraction method: Organic solvents are used to extract lithium ions from lithium-containing solutions, and then converted into lithium oxide through chemical precipitation or other methods. This method can effectively remove certain impurities, but the operation is complex, the cost is high, and new organic impurities are easily introduced; (3) Electrolysis method: Metal lithium is prepared by electrolyzing lithium chloride solution, and then metal lithium is oxidized to lithium oxide. Although this method can obtain a high purity, the process is complex, the energy consumption is high, and it has a greater impact on the environment; (4) Thermal decomposition method of lithium hydroxide: Lithium hydroxide is decomposed at a high temperature above 800 °C to generate lithium oxide. Since the melting point of lithium hydroxide is relatively low, it is extremely easy to form pellets on the surface during high-temperature sintering, but the core of the pellets is still lithium hydroxide and is not completely decomposed by sintering, resulting in low purity of lithium oxide. To improve the product purity, the lithium hydroxide in the center of the pellets needs to be completely decomposed, which requires a higher sintering temperature and extremely high energy consumption; (5) Thermal decomposition method of lithium peroxide: Lithium peroxide is generated by the reaction of lithium hydroxide and hydrogen peroxide, and lithium peroxide is thermally decomposed in a vacuum device to generate lithium oxide. This method has easily controllable operating conditions, a short reaction time, and high product quality, and is a relatively ideal method.

[0025] Lithium oxide is easy to absorb moisture and react with CO2 in the air to form lithium carbonate, resulting in an increase in the carbonate content of the product and a decrease in the lithium oxide content. The crushing and ball milling of massive lithium oxide or coarse particles of hard agglomerates have very high requirements for the humidity and CO2 content of the production equipment and its contact environment.

[0026] At present, there are already some preparation methods for preparing lithium oxide using lithium hydroxide and hydrogen peroxide as raw materials. However, these production processes for preparing lithium oxide using lithium hydroxide and hydrogen peroxide are relatively complex. Generally, high-purity lithium oxide powder products need to be prepared through steps such as preliminary oxidation, deep oxidation, thermal decomposition, and grinding. Moreover, the lithium hydroxide in the raw materials is not recovered, resulting in low raw material utilization rate. Therefore, there is still a need to develop a production process that can prepare high-purity lithium oxide and has a high raw material utilization rate.

[0027] In view of this, the present invention proposes a production process for high-purity lithium oxide, comprising the following steps:

[0028] Mix lithium hydroxide with hydrogen peroxide having a mass concentration of 90% - 99% and carry out a peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide;

[0029] Carry out solid-liquid separation on the mixture containing lithium peroxide and lithium hydroxide to obtain a supernatant containing lithium hydroxide and a solid containing lithium peroxide;

[0030] Carry out a drying treatment on the supernatant containing lithium hydroxide to obtain recovered lithium hydroxide; carry out thermal decomposition on the solid containing lithium peroxide under an inert gas protection atmosphere to obtain high-purity lithium oxide powder.

[0031] The technical solution of the present invention provides a production process of high-purity lithium oxide. Using commercially available battery-grade (or high-purity grade) lithium hydroxide and commercially available hydrogen peroxide as raw materials, the raw material sources are convenient, and no special raw material processing procedures are required. The entire synthesis process is carried out under normal pressure, without the need for complex stepwise oxidation or stepwise thermal decomposition reactions. The operation is convenient, facilitating continuous production. The production process flow is simple, with low energy consumption, and the unreacted lithium hydroxide is recycled, resulting in high raw material utilization rate. In the high-purity lithium oxide production process provided by the present invention, first, lithium hydroxide and hydrogen peroxide are subjected to a peroxidation reaction to generate lithium peroxide. Since there is still unreacted lithium hydroxide in the reaction system, a mixture containing lithium hydroxide and lithium peroxide will be obtained after the reaction. Subsequently, taking advantage of the fact that lithium hydroxide has a high solubility in water while lithium peroxide has a low solubility in water, the mixture containing lithium hydroxide and lithium peroxide is subjected to solid-liquid separation, enabling most of the lithium hydroxide to dissolve in water to form a supernatant, while lithium peroxide forms a solid precipitate, thereby obtaining a supernatant containing lithium hydroxide and a solid containing lithium peroxide. Among them, the solid containing lithium peroxide includes lithium peroxide and part of the lithium hydroxide that has not yet dissolved in water. Subsequently, the supernatant containing lithium hydroxide is dried to recycle the lithium hydroxide dissolved in water. The solid containing lithium peroxide is thermally decomposed under an inert gas protection atmosphere to thermally decompose lithium peroxide and lithium hydroxide to obtain high-purity lithium oxide powder. The lithium oxide product obtained by the technical solution of the present invention has good dispersibility, and the lithium oxide powder product can be obtained without ball milling and pulverization treatment, which is beneficial for subsequent ball milling treatment to prepare ultrafine lithium oxide products. The lithium oxide product prepared by the technical solution of the present invention has high purity, and the raw materials used are commercially available battery-grade (or high-purity grade) lithium hydroxide and commercially available hydrogen peroxide. The raw material sources are convenient, and no special raw material processing procedures are required. The entire synthesis process is carried out under normal pressure, without the need for complex stepwise oxidation or stepwise thermal decomposition reactions. The operation is convenient, facilitating continuous production. The production process flow is simple, with low energy consumption, and high raw material utilization rate. Moreover, in the production process of high-purity lithium oxide of the present invention, the use of ethanol as a dehydrating agent and cleaning agent is avoided, reducing the production cost and the safety and environmental protection risks.

[0032] It should be noted that the technical solution of the present invention can use anhydrous lithium hydroxide (LiOH) to react with hydrogen peroxide, or can also use monohydrate lithium hydroxide (LiOH·H2O) to react with hydrogen peroxide. More preferably, using anhydrous lithium hydroxide to react with hydrogen peroxide can improve the recovery rate of unreacted lithium hydroxide. This is because monohydrate lithium hydroxide is more soluble in water than anhydrous lithium hydroxide. Under the same conditions, monohydrate lithium hydroxide is more inclined to remain in the solution, while anhydrous lithium hydroxide is relatively more likely to precipitate out of the solution or be filtered out. Therefore, it is more difficult to perform solid-liquid separation on monohydrate lithium hydroxide compared to anhydrous lithium hydroxide.

[0033] In an embodiment of the present invention, the mass ratio of lithium hydroxide to hydrogen peroxide is 1:(1.5 - 5). Exemplarily, the mass ratio of lithium hydroxide to hydrogen peroxide can be 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5. As the amount of hydrogen peroxide used increases, it is beneficial to improve the purity of the final lithium oxide product. Setting the mass ratio of lithium hydroxide to hydrogen peroxide within the above range allows the peroxidation reaction between lithium hydroxide and hydrogen peroxide to proceed fully, which is beneficial for controlling production costs and the purity of the final lithium oxide product.

[0034] In an embodiment of the present invention, the thermal decomposition temperature is 600 - 800 °C. Exemplarily, the temperature of the thermal decomposition can be 600 °C, 650 °C, 700 °C, 750 °C or 800 °C. Controlling the thermal decomposition temperature within the above range is beneficial for obtaining a lithium oxide product with high purity and small particle size, while controlling energy consumption.

[0035] In an embodiment of the present invention, the thermal decomposition time is 10 - 20 h. Exemplarily, the time of the peroxidation reaction can be 10 h, 12 h, 14 h, 16 h, 18 h or 20 h. Controlling the thermal decomposition time within the above range is beneficial for obtaining a lithium oxide product with high purity, while controlling energy consumption.

[0036] In an embodiment of the present invention, the temperature of the peroxidation reaction is 0 - 10 °C. Controlling the temperature of the peroxidation reaction at ≤10 °C helps to reduce the possibility of hydrogen peroxide decomposing into water and oxygen, improves the utilization rate of hydrogen peroxide, and moreover, the hydrogen peroxide used in the present invention is high-concentration hydrogen peroxide, and low temperature is beneficial for controlling the reaction to proceed gently.

[0037] In an embodiment of the present invention, the time of the peroxidation reaction is 10 - 36 h. Exemplarily, the time of the peroxidation reaction can be 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h or 36 h. Setting the time of the peroxidation reaction within the above range can allow the reaction to proceed fully, ensuring that more raw materials are converted into lithium peroxide.

[0038] In an embodiment of the present invention, in the step of mixing lithium hydroxide and hydrogen peroxide with a mass concentration of 90% - 99% and performing a peroxidation reaction, the particle size of the lithium hydroxide is 1 - 20 μm. Herein, the particle size refers to the average particle size. Using a lithium hydroxide particle size of 1 - 20 μm can help optimize the yield and improve the purity of the final product. More preferably, the particle size of the lithium hydroxide is selected to be 1 - 10 μm, which is beneficial for obtaining a lithium oxide powder with high purity and small particle size.

[0039] In an embodiment of the present invention, in the step of mixing lithium hydroxide and hydrogen peroxide with a mass concentration of 90% to 99% and performing a peroxidation reaction, the purity of the lithium hydroxide is not less than 99.5%. The higher the purity of lithium hydroxide, the higher the purity of the prepared lithium oxide. The technical solution of the present invention uses lithium hydroxide with a purity of not less than 99.5%.

[0040] In an embodiment of the present invention, in the step of drying the supernatant containing lithium hydroxide to obtain recycled lithium hydroxide, the drying method includes evaporation using a high-efficiency evaporator.

[0041] In an embodiment of the present invention, in the step of thermally decomposing the solid containing lithium peroxide under an inert gas protection atmosphere, the inert gas includes nitrogen.

[0042] In an embodiment of the present invention, after the step of thermally decomposing the solid containing lithium peroxide under an inert gas protection atmosphere to obtain high-purity lithium oxide powder, it further includes packaging the high-purity lithium oxide powder under nitrogen protection.

[0043] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0044] In the following embodiments, the lithium hydroxide used is commercially available battery-grade lithium hydroxide or commercially available high-purity lithium hydroxide. The hydrogen peroxide used is commercially available hydrogen peroxide with a mass concentration of 98%.

[0045] Example 1

[0046] A production process of high-purity lithium oxide includes the following steps:

[0047] (1) Add 10 g of anhydrous lithium hydroxide (particle size 1 - 3 μm) and 30 g of hydrogen peroxide with a mass concentration of 98% to a reactor, stir and mix evenly, control the temperature of the reactor at 10°C, continuously stir for 24 h, perform a peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide;

[0048] (2) Perform solid-liquid separation on the obtained mixture containing lithium peroxide and lithium hydroxide through a high-speed centrifuge to obtain a supernatant containing lithium hydroxide and a solid containing lithium peroxide;

[0049] (3) Evaporate the liquid from the supernatant containing lithium hydroxide through a high-efficiency evaporator to complete the recovery of lithium hydroxide; place the solid containing lithium peroxide in a roller hearth furnace under a nitrogen protection atmosphere, calcine at 650°C for 12 h to obtain 4.55 g of high-purity lithium oxide powder, and package the high-purity lithium oxide powder under nitrogen protection.

[0050] Example 2

[0051] Compared with Example 1, the difference lies in that the mass ratio of lithium hydroxide to hydrogen peroxide is 1:1.5.

[0052] Example 3

[0053] Compared with Example 1, the difference lies in that the mass ratio of lithium hydroxide to hydrogen peroxide is 1:3.5.

[0054] Example 4

[0055] Compared with Example 1, the difference lies in that the temperature during thermal decomposition is 600 °C.

[0056] Example 5

[0057] Compared with Example 1, the difference lies in that the temperature during thermal decomposition is 750 °C.

[0058] Example 6

[0059] Compared with Example 1, the difference lies in that the time during thermal decomposition is 10 h.

[0060] Example 7

[0061] Compared with Example 1, the difference lies in that the time during thermal decomposition is 20 h.

[0062] Example 8

[0063] Compared with Example 1, the difference lies in that the particle size of lithium hydroxide is 5 - 10 μm.

[0064] Example 9

[0065] Compared with Example 1, the difference lies in that the particle size of lithium hydroxide is 15 - 20 μm.

[0066] Comparative Example 1

[0067] Compared with Example 1, the difference lies in that the mass concentration of hydrogen peroxide is 20%.

[0068] Comparative Example 2

[0069] Compared with Example 1, the difference lies in that the temperature during thermal decomposition is 400 °C.

[0070] Comparative Example 3

[0071] Compared with Example 1, the difference lies in that the temperature during thermal decomposition is 500 °C.

[0072] Comparative Example 4

[0073] Compared with Example 1, the difference lies in that the time during thermal decomposition is 6 h.

[0074] Comparative Example 5

[0075] Compared with Example 1, the difference is that the time during thermal decomposition is 9 h.

[0076] Comparative Example 6

[0077] A preparation method of lithium oxide (refer to CN115650263B), comprising the following steps:

[0078] (1) Synthesis of lithium peroxide with low water content:

[0079] In a reaction vessel, 470 mL of hydrogen peroxide (the molar ratio of hydrogen peroxide to lithium hydroxide monohydrate is 1.32) was added. 220 g of lithium hydroxide monohydrate was taken and slowly added to the hydrogen peroxide; the mixture was stirred and reacted at a temperature of 20 - 30 °C for 2 h; then the temperature was raised to 35 - 45 °C and stirred and reacted for 3 h. Then the temperature was raised to 99.0 °C (the heating rate was 0.4 - 0.6 °C / min) and stirred and reacted for 2.0 h; solid-liquid separation was carried out to obtain 112.19 g of solid-phase product.

[0080] (2) Dehydration of the synthesis product of lithium peroxide:

[0081] 100.00 g of the synthesis product was placed in a stainless-steel container and put into a vacuum drying oven, and vacuum-dried at room temperature (15 °C) for 6 hours, and the weight loss rate was 15.32%. The dehydrated product was 84.68 g. Among them, the proportion of Li₂O₂ was 92.63%, the proportion of Li₂O₂ with crystal water was 5.46%, and the proportion of Li₂CO₃ was 1.91%.

[0082] (3) Thermal decomposition of the dehydrated product of lithium peroxide:

[0083] The dehydrated product of lithium peroxide (65.00 g) was loaded into a platinum crucible and placed in a vacuum furnace. After evacuating to a vacuum at room temperature for 10 min (vacuum degree 45 Pa), the temperature was raised to 450 °C and held for 1.5 h; the temperature was raised to 540 °C and held for 1.5 h; the temperature was raised to 820 °C and held for 4 h; then the temperature was lowered to 30 °C under vacuum conditions, the product was discharged, bagged, and sealed to obtain 40.59 g of product.

[0084] Result: The lithium oxide content of the obtained product was 99.30%. From the feedstock to obtaining the product, the direct recovery rate of Li was 75.18%, D 50 was 50 - 80 μm.

[0085] Comparative Example 7

[0086] A preparation method of lithium oxide (refer to CN109336139A), comprising the following steps:

[0087] (1) Mixing: Add 2000 mL of hydrogen peroxide with a concentration of 30% into the reaction vessel and stir. While stirring, slowly add 1.6 kg of lithium hydroxide monohydrate with a purity of 99.9% into the reaction vessel. After the feeding is completed, continue to stir for 3 min to obtain a uniformly mixed solution. During the mixing process, control the temperature at about 25 °C by means of an ice bath.

[0088] (2) Preliminary oxidation: Place the reaction vessel in a vacuum drying oven, evacuate to -0.01 MPa, adjust the temperature to 80 °C, and keep it warm for 4 hours to obtain lithium peroxide containing crystal water.

[0089] (3) Deep oxidation: Adjust the temperature in the vacuum drying oven to 130 °C, keep the vacuum degree at -0.01 MPa, and keep it warm for 4 hours to remove the crystal water and obtain lithium peroxide.

[0090] (4) Thermal decomposition: Adjust the temperature in the vacuum drying oven to 350 °C, keep the vacuum degree at -0.01 MPa, and keep it warm for 4 hours to obtain lithium oxide with a relatively high purity.

[0091] (5) Purification: Adjust the temperature in the vacuum drying oven to 600 °C, keep the vacuum degree at -0.01 MPa, and keep it warm for 4 hours to obtain 0.868 kg of lithium oxide with a high purity (the lithium oxide content in the obtained product is 99.87%), and the yield is 99.21%.

[0092] (6) Ball milling and sieving: Take out the lithium oxide with a high purity obtained in the purification step, carry out ball milling, control the rotation speed of the ball mill at 300 revolutions / min, and the ball milling time at 30 min, and then carry out sieving to control the particle size of the product at D50 50 nm.

[0093] Performance testing

[0094] Test the purity, yield, and particle size of the lithium oxide prepared in Examples 1-9 and Comparative Examples 1-7. The test results are shown in Table 1.

[0095] Method for testing the purity of lithium oxide: Test the purity of lithium oxide by X-ray fluorescence spectrometry (XRF). The test results are shown in Table 1.

[0096] Method for testing the yield of lithium oxide: The calculation formula for the yield of lithium oxide is: (weight of actually obtained lithium oxide / weight of lithium oxide that can be obtained by complete conversion of raw materials theoretically) × 100%. The test results are shown in Table 1.

[0097] Method for testing the particle size: Test the Dv50 particle size of lithium oxide with a particle size detector. The test results are shown in Table 1.

[0098] Table 1 Parameters and test results of Examples 1-9 and Comparative Examples 1-7

[0099]

[0100]

[0101] As can be seen from Table 1, the purity of lithium oxide in Examples 1-8 is greater than 95%, and the highest can reach more than 99.9%, which is better than the purity test results of Comparative Example 6 (99.3%) and Comparative Example 7 (99.87%).

[0102] According to the test results of Examples 1-3, the greater the dosage of hydrogen peroxide, the higher the yield of lithium oxide; according to the test results of Examples 1 and 4-5, the higher the thermal decomposition temperature, the higher the purity of lithium oxide and the larger the particle size; according to the test results of Examples 1 and 6-7, the longer the thermal decomposition time, the higher the purity of lithium oxide and the larger the particle size; according to the test results of Examples 1, 8-9, the larger the particle size of the raw material lithium hydroxide, the lower the purity of the prepared lithium oxide and the larger the particle size.

[0103] According to the test results of Example 1 and Comparative Example 1, when using hydrogen peroxide with a low concentration, the yield of lithium oxide becomes lower, the purity becomes lower, and the particle size becomes larger; according to the test results of Example 1 and Comparative Examples 2-3, a thermal decomposition temperature lower than 600 °C will cause the purity of lithium oxide to become lower; according to the test results of Example 1 and Comparative Examples 4-5, a thermal decomposition time lower than 10 h will cause the purity of lithium oxide to become lower.

[0104] The above are only exemplary embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the technical concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A production process for high-purity lithium oxide, characterized in that: The following steps are involved: Mixing lithium hydroxide and hydrogen peroxide with a mass concentration of 90% to 99% to perform a peroxidation reaction to obtain a mixture containing lithium peroxide and lithium hydroxide; The mixture containing lithium peroxide and lithium hydroxide is subjected to solid-liquid separation to obtain a supernatant containing lithium hydroxide and a solid containing lithium peroxide; The supernatant containing lithium hydroxide is dried to obtain recovered lithium hydroxide; the solid containing lithium peroxide is thermally decomposed under an inert gas protective atmosphere to obtain high-purity lithium oxide powder.

2. The production process of high-purity lithium oxide according to claim 1, characterized in that: The mass ratio of the lithium hydroxide to the hydrogen peroxide is 1:(1.5-5).

3. The production process of high-purity lithium oxide according to claim 1, characterized in that: The thermal decomposition temperature is 600-800° C.; and / or, The thermal decomposition time is 10 to 20 hours.

4. The production process of high-purity lithium oxide according to claim 1, characterized in that: The temperature of the peroxidation reaction is 0-10°C.

5. The production process of high-purity lithium oxide according to claim 1, characterized in that: The peroxidation reaction time is 10 to 36 hours.

6. The production process of high-purity lithium oxide according to claim 1, characterized in that: In the step of mixing lithium hydroxide and hydrogen peroxide with a mass concentration of 90% to 99% to perform a peroxidation reaction, the particle size of the lithium hydroxide is 1 to 20 μm.

7. The production process of high-purity lithium oxide according to claim 1, characterized in that: In the step of mixing lithium hydroxide and hydrogen peroxide with a mass concentration of 90% to 99% to perform a peroxidation reaction, the purity of the lithium hydroxide is not less than 99.5%.

8. The production process of high-purity lithium oxide according to claim 1, characterized in that: In the step of drying the supernatant containing lithium hydroxide to obtain recovered lithium hydroxide, the drying method includes evaporating using a high-efficiency evaporator.

9. The production process of high-purity lithium oxide according to claim 1, characterized in that: In the step of thermally decomposing the solid material containing lithium peroxide under an inert gas protective atmosphere, the inert gas includes nitrogen.

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