Anhydrous lithium iodide with low water content as well as preparation method and application thereof

Abstract

The invention discloses low-water-content anhydrous lithium iodide as well as a preparation method and application thereof, and relates to the technical field of lithium iodide production. The ceramic grinding balls are added into the lithium iodide trihydrate concentrated solution for vacuum heating and drying, so that autolysis of lithium iodide in the drying process can be effectively avoided, water in the lithium iodide trihydrate concentrated solution can be removed in a targeted manner, and meanwhile, due to the fact that the ceramic grinding balls are added for vacuum heating and drying, the drying efficiency of the lithium iodide trihydrate concentrated solution is improved. After drying is finished, ball milling can be directly carried out, operation steps are saved, and after ball milling is finished, open drying is carried out, so that moisture generated in the transferring process of the anhydrous lithium iodide coarse material can be quickly, simply and conveniently removed. The preparation method can obtain the anhydrous lithium iodide with low water content, has the advantages of simple operation, mild reaction conditions and low operation cost, and is beneficial to large-scale production of the anhydrous lithium iodide with low water content.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium iodide production, in particular to low-moisture anhydrous lithium iodide and a preparation method and application thereof. BACKGROUND

[0002] Anhydrous lithium iodide (LiI) is an important inorganic compound and has wide application prospects in the fields of batteries, catalysts and organic synthesis. In the field of batteries, anhydrous lithium iodide is the core electrolyte material of lithium-iodine batteries, and the purity and performance of the anhydrous lithium iodide directly affect the energy density, cycle life and safety of the batteries. Due to the characteristics of high energy density, long cycle life and good safety, lithium-iodine batteries have great application potential in the fields of medical devices, aerospace and military industry. In addition, anhydrous lithium iodide can also be used as a catalyst in organic synthesis and plays an important role in the synthesis of pharmaceutical intermediates and fine chemicals. However, lithium iodide itself has strong deliquescence and hydrate stability, which brings difficulties to the storage and transportation of lithium iodide and limits the application of anhydrous lithium iodide in high-performance lithium-iodine batteries and high-end catalytic fields.

[0003] Lithium iodide is one of the substances with the strongest deliquescence among all alkali metal halides, which means that once there is water in its environment, it will spontaneously and strongly absorb water vapor in the air to form very stable crystalline hydrates, such as lithium iodide dihydrate and lithium iodide trihydrate. The water molecules in these hydrates are tightly bound to Li+ ions through coordination bonds, but in the process of battery application or catalyst application in some reaction environments, the water in lithium iodide will seriously affect the quality of the product. For example, in battery applications, the water in the electrolyte will have a side reaction with the metal lithium negative electrode, leading to battery performance degradation and even safety hazards; in catalyst applications, the presence of impurities will affect the selectivity and yield of the reaction.

[0004] Since the stability of water-containing lithium iodide is higher than that of anhydrous lithium iodide, a high energy is required to drive off the crystalline water in lithium iodide, so how to reduce the water content in anhydrous lithium iodide is one of the keys to improving the quality of anhydrous lithium iodide. The current methods for reducing the water content in anhydrous lithium iodide have defects such as simple operation method but high water content, or low water content but complex operation method, or harsh reaction conditions, or high reaction cost, etc.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a low-moisture anhydrous lithium iodide and a preparation method and application thereof.

[0007] The present application is implemented as follows: In a first aspect, the present application provides a preparation method of low-water-content anhydrous lithium iodide, comprising adding ceramic grinding balls to a concentrated lithium iodide trihydrate solution for vacuum heating and drying, obtaining an anhydrous lithium iodide crude material, then ball milling the anhydrous lithium iodide crude material under a humidity of less than 2.0%, and open-drying the ball-milled material to obtain the low-water-content anhydrous lithium iodide.

[0008] In a second aspect, the present application provides a low-water-content anhydrous lithium iodide prepared by the preparation method of any one of the preceding embodiments.

[0009] In a third aspect, the present application provides use of the preparation method of any one of the preceding embodiments in the preparation of a battery or a catalyst.

[0010] The present application has the following advantages: The present application provides a low-water-content anhydrous lithium iodide, a preparation method thereof, and use thereof. By adding ceramic grinding balls to a concentrated lithium iodide trihydrate solution for vacuum heating and drying, the present application can effectively prevent the lithium iodide from self-dissolving during drying, thereby enabling targeted removal of water from the concentrated lithium iodide trihydrate solution. In addition, since the ceramic grinding balls are added for vacuum heating and drying, the ball milling can be directly performed after the drying is completed, thereby saving operation steps. After the ball milling is completed, the anhydrous lithium iodide crude material is dried again, thereby removing the water generated during the transfer of the anhydrous lithium iodide crude material and improving the purity of the anhydrous lithium iodide. The above preparation method can obtain anhydrous lithium iodide with low water content, and has the advantages of simple operation, mild reaction conditions, and low operation cost, thereby facilitating large-scale production of low-water-content anhydrous lithium iodide. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0012] Figure 1 The flow chart of the preparation method of low-water-content anhydrous lithium iodide provided by the embodiments of the present application. DETAILED DESCRIPTION

[0013] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are used. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased on the market are used.

[0014] The features and performances of the present application will be further described in detail below with reference to the embodiments.

[0015] The hygroscopicity of anhydrous lithium iodide is very good, and once it comes into contact with water, it will spontaneously and strongly absorb water vapor in the air to form very stable crystalline hydrates. The water molecules in these hydrates are tightly bound to Li+ ions through coordination bonds and are difficult to separate. The temperature required to completely remove the water molecules is usually harsh, which means that continuous high-temperature treatment is required.

[0016] There are currently methods for treating water-containing lithium iodide using spray drying, but spray drying is a rapid drying process, and it is difficult to completely remove the stable crystalline water in lithium iodide in a short period of time, so water residues are easily left behind, resulting in low purity of lithium iodide. Some other methods for synthesizing anhydrous lithium iodide directly using a solid-phase method usually need to be carried out in a vacuum environment and require subsequent organic purification, which is harsh and difficult to achieve industrial production. Although the vacuum sublimation method can obtain high-purity products, it has high energy consumption and low yield. Therefore, the inventors propose the following solution.

[0017] In a first aspect, the present application provides a method for preparing low-water-content anhydrous lithium iodide, which comprises adding ceramic grinding balls to a concentrated lithium iodide trihydrate solution for vacuum heating and drying, obtaining an anhydrous lithium iodide crude material, and then ball milling the anhydrous lithium iodide crude material under a humidity of less than 2.0%, and finally drying the ball-milled material in the open air to obtain low-water-content anhydrous lithium iodide.

[0018] Conventional water removal processes are mostly through temperature drying to remove water from the product. However, the strong hygroscopicity of lithium iodide makes it difficult to completely remove water, and only the water content in the molecules can be reduced as much as possible. In addition, lithium iodide itself exhibits certain ionic conductivity below its melting point (449°C). During the drying process, the temperature continues to rise, and the ionic thermal motion intensifies, which more easily leads to autolysis of the water-containing lithium iodide during the drying process. After autolysis, water and lithium iodide cannot be separated. Therefore, how to avoid autolysis of water-containing lithium iodide during the drying process is one of the technical problems in the field.

[0019] The present application can effectively avoid autolysis of lithium iodide during the drying process by adding ceramic grinding balls to the concentrated lithium iodide trihydrate solution for vacuum heating and drying, thereby enabling targeted removal of water from the concentrated lithium iodide trihydrate solution. In addition, since ceramic grinding balls are added for vacuum heating and drying, the ball milling can be directly performed after the drying is completed, saving operation steps. After ball milling, the water content in the anhydrous lithium iodide crude material produced during the transfer process can be removed. The above preparation method can obtain anhydrous lithium iodide with low water content, and has the advantages of simple operation, mild reaction conditions, and low operation cost, which is beneficial to large-scale production of low-water-content anhydrous lithium iodide.

[0020] Please refer to Figure 1In an optional embodiment, the present application provides a method for preparing anhydrous lithium iodide with low water content, comprising the following steps: S01, preparing a concentrated solution of lithium iodide trihydrate S011, preparing a solution of lithium iodide trihydrate The solution of lithium iodide trihydrate provided by the present application includes a reaction solution obtained in the process of synthesizing lithium iodide trihydrate or a solution of lithium iodide trihydrate obtained by reconstituting commercially available lithium iodide trihydrate. Therefore, the method provided by the present application does not limit the source of lithium iodide trihydrate, and can achieve the effect of reducing water content.

[0021] In an optional embodiment, the process of synthesizing lithium iodide trihydrate can use hydroiodic acid and lithium hydroxide to react, thereby obtaining a reaction solution containing lithium iodide trihydrate. In the hydroiodic acid, the molar ratio of I - to Li + in the lithium hydroxide is 1:0.8-1.2.

[0022] In an optional embodiment, the process of synthesizing lithium iodide trihydrate can also use a mixture of elemental iodine, water, hydrazine and lithium hydroxide to react, thereby obtaining a reaction solution containing lithium iodide trihydrate. In the lithium hydroxide, the molar ratio of I

[0023] S012, heating and concentrating The solution of lithium iodide trihydrate obtained in step S011 is heated and concentrated to obtain a concentrated solution of lithium iodide trihydrate. Heating and concentrating can remove most of the water outside the lithium iodide trihydrate molecules to reduce the difficulty of subsequent drying.

[0024] Preferably, the temperature of heating and concentrating is 100-150°C, and the time is 2-4h, so as to remove most of the water in the solution of lithium iodide trihydrate.

[0025] Preferably, in order to avoid impurities and ensure the purity of lithium iodide, inert gas is used as protective gas during the process of heating and concentrating, and the inert gas includes argon or nitrogen.

[0026] Preferably, in order to ensure uniform dehydration during the process of heating and concentrating, stirring is maintained during the process of heating and concentrating, and the stirring speed is 100-150rpm.

[0027] Preferably, heating and concentrating is carried out in a vertical reaction kettle, and the material contacting part of the vertical reaction kettle is lined with TA2.

[0028] S02, vacuum heating and drying In the concentrated solution of lithium iodide trihydrate obtained in step S012, ceramic grinding balls are added, and preferably, the ceramic grinding balls include alumina balls and / or zirconia balls. The ceramic grinding balls act as fillers and can prevent the formation of a complete gel film on the surface of lithium iodide trihydrate due to uneven heating during the concentration process.

[0029] Preferably, the liquid-solid ratio of the lithium iodide trihydrate concentrate and the ceramic grinding balls is 4-6:1, by adding the above-mentioned content of ceramic grinding balls, it is beneficial to ensure that the lithium iodide trihydrate concentrate can be uniformly dehydrated in the process of drying, while effectively avoiding the formation of a gelatinous film of lithium iodide self-dissolution in the low-temperature drying process.

[0030] Further, the lithium iodide trihydrate concentrate containing the ceramic grinding balls is vacuum heated and dried to obtain the lithium iodide anhydrous crude material.

[0031] Preferably, the vacuum heating and drying includes a first stage and a second stage, the heating temperature of the first stage is 60-80℃, and the drying time is 4-6h; the heating temperature of the second stage is 260-300℃, and the drying time is 4-6h.

[0032] Preferably, the heating rate of the vacuum heating and drying process is 1-3℃ / min, and the vacuum degree is ≤0.1bar.

[0033] By controlling the heating temperature of the first stage within the above-mentioned range, the formation of a gelatinous film of lithium iodide self-dissolution can be effectively avoided, and by prolonging the drying time of the first stage, the first molecular water in the lithium iodide trihydrate can be removed, and at the same time, favorable conditions are created for the removal of the second and third molecular water. After the first stage, the temperature is slowly raised to the second stage, so as to remove the second and third molecular water in the lithium iodide trihydrate, and obtain the solid lithium iodide anhydrous crude material.

[0034] Preferably, in order to ensure that the lithium iodide trihydrate can be uniformly dehydrated in the process of vacuum heating and drying, stirring is maintained during the process of vacuum heating and drying, the stirring speed of the first stage is 15-25rpm, and the stirring speed of the second stage is 8-12rpm.

[0035] Preferably, the vacuum heating and drying uses a vacuum rake dryer, and the material of the dryer is TA2, which can effectively avoid the corrosion of acidic components and basic components in the raw materials to the metal material, and at the same time, the problem of easy decomposition of lithium iodide under light is avoided.

[0036] S03, ball milling and secondary drying The lithium iodide anhydrous crude material obtained in S02 is subjected to ball milling, since ceramic grinding balls have been added in S02, the product of S02 can be directly placed in the ball milling tank for ball milling, saving the operation steps.

[0037] In an optional embodiment, the ball milling comprises dry ball milling or wet ball milling; preferably, the ball milling adopts dry ball milling. The dry ball milling can directly ball mill the product of the S02 step without additional addition of other raw materials, the operation method is simple, and the post-treatment after the ball milling is completed is difficult. The wet ball milling needs to remove the organic solvent after the ball milling is completed, the post-treatment is relatively difficult, and the raw material cost and the post-treatment cost of the organic solvent are additionally increased.

[0038] Preferably, the rotation speed of the dry ball milling is 300-400 rpm, and the ball milling time is 2-3 h. By controlling the ball milling parameters in the above range, the particle size of the anhydrous lithium iodide crude material can be reduced.

[0039] Preferably, in order to avoid the introduction of water during the ball milling, the ball milling process is carried out in a glove box, and the water content in the glove box is less than 50 ppm.

[0040] Further, after the ball milling is completed, the anhydrous lithium iodide crude material is directly subjected to open drying to remove the water absorbed by the anhydrous lithium iodide crude material during the transfer process.

[0041] Preferably, the drying temperature of the open drying is 100-120℃, the drying time is 1-2 h, the open drying is still carried out in the glove box, and the atmosphere in the glove box is inert atmosphere.

[0042] Preferably, the inert atmosphere comprises nitrogen or argon.

[0043] Preferably, in order to ensure that the water of the anhydrous lithium iodide crude material can be uniformly removed, the open drying process is kept stirring, and the stirring rotation speed is 20-40 rpm.

[0044] The S03 step is carried out in the glove box throughout, and the atmosphere and humidity in the glove box are controlled, which effectively avoids the absorption of water by the lithium iodide. After the particle size of the anhydrous lithium iodide crude material is refined, dehydration is carried out, which can improve the dehydration effect; at the same time, the open drying can directly utilize the self-purification system of the glove box to purify the water in the environment, which is simpler in operation, and does not need to be additionally purified.

[0045] In a second aspect, the present application provides a low-water-content anhydrous lithium iodide prepared by the preparation method of any one of the preceding embodiments.

[0046] In a third aspect, the present application provides an application of the preparation method of any one of the preceding embodiments in the preparation of a battery or a catalyst.

[0047] Example 1 The present embodiment provides a preparation method of a low-water-content anhydrous lithium iodide, comprising the following steps: S01, preparation of lithium iodide trihydrate concentrated solution S011, Preparation of lithium iodide trihydrate solution The neutralization reaction is carried out with hydriodic acid and lithium hydroxide monohydrate as raw materials to obtain a reaction solution containing lithium iodide trihydrate, i.e. lithium iodide trihydrate solution. In the hydriodic acid, the molar ratio of I - to Li + in the lithium hydroxide is 1:1.

[0048] S012, Heating and concentration The lithium iodide trihydrate solution obtained in S011 is placed in a vertical reaction kettle for heating and concentration. The vertical reaction kettle is in a nitrogen atmosphere, the heating and concentration temperature is 120℃, the time is 3h, stirring is maintained during the heating and concentration process, the stirring speed is 120rpm, and the lithium iodide trihydrate concentrated solution is obtained after concentration. The material contacting part of the vertical reaction kettle is made of TA2.

[0049] S02, Vacuum heating and drying Zirconium oxide balls are added to the lithium iodide trihydrate concentrated solution obtained in S012, and the liquid-solid ratio of the lithium iodide trihydrate concentrated solution and the ceramic grinding balls is 5:1.

[0050] The above lithium iodide trihydrate concentrated solution containing ceramic grinding balls is placed in a vacuum rake dryer for vacuum heating and drying, the material of the dryer is TA2, and the anhydrous lithium iodide crude material is obtained after drying.

[0051] The vacuum heating and drying includes a first stage and a second stage, the heating temperature of the first stage is 70℃, and the drying time is 5h; the heating temperature of the second stage is 280℃, and the drying time is 5h; the heating rate of the vacuum heating and drying process is 2℃ / min, and the vacuum degree is 0.1bar.

[0052] In order to ensure that the lithium iodide trihydrate can be uniformly dehydrated during the vacuum heating and drying process, stirring is maintained during the vacuum heating and drying process, the stirring speed of the first stage is 20rpm, and the stirring speed of the second stage is 10rpm.

[0053] S03, Ball milling and secondary drying The anhydrous lithium iodide crude material obtained in S02 and ceramic grinding balls are transferred together into a ball mill jar for dry ball milling, the ball milling speed is 400rpm, and the ball milling time is 2h. The ball milling process is carried out in a glove box, the atmosphere in the glove box is nitrogen atmosphere, and the water content is less than 50ppm. After the ball milling is completed, the anhydrous lithium iodide crude material is directly subjected to open drying to remove the water absorbed by the anhydrous lithium iodide crude material during the transfer process.

[0054] The drying temperature of the open drying is 120℃, the drying time is 1h, the open drying is still carried out in the glove box, and stirring is maintained during the open drying process, and the stirring speed is 20rpm.

[0055] The present example also provides a low water content anhydrous lithium iodide, which is prepared by the above method, and is numbered as LiI-1.

[0056] Example 2 The present example provides a method for preparing a low water content anhydrous lithium iodide, and the specific steps are similar to those of Example 1, except that the lithium iodide trihydrate solution in step S011 is obtained by reconstituting commercially available lithium iodide trihydrate. The commercially available lithium iodide trihydrate is purchased from Shanghai Ougin Industrial Co., Ltd. (500 g / bottle, analytical pure).

[0057] The present example also provides a low water content anhydrous lithium iodide, which is prepared by the above method, and is numbered as LiI-2.

[0058] Example 3 The present example provides a method for preparing a low water content anhydrous lithium iodide, and the specific steps are similar to those of Example 1, except that step S011 is different, specifically as follows: S011, preparation of lithium iodide trihydrate solution Elemental iodine, water, hydrazine, and lithium hydroxide monohydrate are used as raw materials to react and obtain a reaction solution containing lithium iodide trihydrate, i.e. a lithium iodide trihydrate solution. The molar ratio of lithium hydroxide to iodine is 2:1.1.

[0059] The present example also provides a low water content anhydrous lithium iodide, which is prepared by the above method, and is numbered as LiI-3.

[0060] Comparative Example 1 The present comparative example provides a method for preparing a low water content anhydrous lithium iodide, and the specific steps are similar to those of Example 1, except that after ball milling in step S03, the anhydrous lithium iodide crude material is obtained directly without secondary drying.

[0061] The present comparative example also provides a low water content anhydrous lithium iodide, which is prepared by the above method, and is numbered as LiI-DB1.

[0062] Comparative Example 2 The present comparative example provides a method for preparing a low water content anhydrous lithium iodide, and the specific steps are similar to those of Example 1, except that step S03 is different, specifically as follows: S03, ball milling and secondary drying The anhydrous lithium iodide crude material obtained in step S02 and the ceramic milling balls are transferred together into a ball mill tank for dry ball milling, with a rotation speed of 400 rpm and a ball milling time of 2 h. The ball milling process is carried out in a glove box, and the atmosphere in the glove box is nitrogen with a water content of less than 50 ppm. After the ball milling is completed, the anhydrous lithium iodide crude material is subjected to air drying to remove the water absorbed during the transfer process.

[0063] The parameters of the aeration drying include: aeration drying temperature of 180℃, drying for 4h, nitrogen as the gas source, and a gas flow rate of 1.5L / min. The process is completed in a glove box.

[0064] The present comparative example also provides a low-moisture anhydrous lithium iodide prepared by the above method, which is numbered as LiI-DB2.

[0065] Comparative Example 3 The present comparative example provides a method for preparing a low-moisture anhydrous lithium iodide, which is similar to the specific steps of Example 1, and the only difference is that the S02 step is different, and the specific steps are as follows: S02, spray drying The lithium iodide trihydrate concentrated solution obtained in the S012 step is directly subjected to spray drying, and the spray drying temperature is 300℃.

[0066] The present comparative example also provides a low-moisture anhydrous lithium iodide prepared by the above method, which is numbered as LiI-DB3.

[0067] Comparative Example 4 The present comparative example provides a method for preparing a low-moisture anhydrous lithium iodide, which is similar to the specific steps of Example 1, and the only difference is that: in the S02 step, no ceramic grinding balls are used during vacuum heating and drying; and after the vacuum heating and drying is completed, the ball milling is performed according to a mass ratio of the ceramic grinding balls to the anhydrous lithium iodide of 4:1.

[0068] The present comparative example also provides a low-moisture anhydrous lithium iodide prepared by the above method, which is numbered as LiI-DB4.

[0069] Comparative Example 5 The present comparative example provides a method for preparing a low-moisture anhydrous lithium iodide, which is similar to the specific steps of Example 1, and the only difference is that: in the S02 step, the liquid-solid ratio of the lithium iodide trihydrate concentrated solution to the ceramic grinding balls is 2:1.

[0070] The present comparative example also provides a low-moisture anhydrous lithium iodide prepared by the above method, which is numbered as LiI-DB5.

[0071] Comparative Example 6 The present comparative example provides a method for preparing a low-moisture anhydrous lithium iodide, which is similar to the specific steps of Example 1, and the only difference is that: in the S02 step, the liquid-solid ratio of the lithium iodide trihydrate concentrated solution to the ceramic grinding balls is 8:1. During the ball milling, the material (i.e., the lithium iodide trihydrate in the process of vacuum heating and drying) will sink to the bottom.

[0072] The present comparative example also provides a low-moisture anhydrous lithium iodide prepared by the above method, which is numbered as LiI-DB6.

[0073] Comparative Example 7 The comparative example provides a preparation method of low water content anhydrous lithium iodide, and the specific steps are similar to those of Example 1, and the only difference is that the S03 step is replaced by vacuum drying instead of open drying, and the vacuum drying parameters are 80 DEG C and 4h.

[0074] The comparative example also provides a low water content anhydrous lithium iodide prepared by the above method, and the number is LiI-DB7.

[0075] Test Example 1 The low water content anhydrous lithium iodide provided by Examples 1-3 and Comparative Examples 1-7 is tested for purity and water content, and the results are shown in Table 1.

[0076] The purity test uses inductively coupled plasma mass spectrometry (ICP), and the water content test uses a Karl Fischer moisture detector.

[0077] Table 1 Properties of low water content anhydrous lithium iodide

[0078] As can be seen from Table 1, in the process of vacuum heating and drying, ceramic grinding balls are added, and the parameters of vacuum heating and drying are controlled, so that the water in lithium iodide trihydrate is removed, and anhydrous lithium iodide is obtained. The coarse material is first transferred to a glove box, and then ball milled to reduce the water absorption rate of the anhydrous lithium iodide coarse material during the transfer process. After ball milling and crushing, the semi-crystalline water absorbed during the transfer process of the anhydrous lithium iodide coarse material can be quickly removed by open drying, further reducing the water content of the product. In addition, the method provided by the present application has high industrial equipment applicability throughout the process, and can be put into production by simply designing the gas path and material path. The method for preparing high-purity anhydrous lithium iodide has the advantages of low water content, high purity, and high equipment adaptation.

[0079] Comparative Example 1 does not have the S03 step, and the anhydrous lithium iodide coarse material absorbs water during the transfer process, resulting in a higher water content in the final test, which is nearly five times that of Example 1, which is not conducive to the application of anhydrous lithium iodide in the battery or catalyst field.

[0080] Comparative Example 2 uses other secondary drying methods (air drying), and the anhydrous lithium iodide product obtained has a slightly lower water content than Comparative Example 1, but the water content is still significantly higher than that of the present application, so the open drying provided by the present application can not only achieve rapid drying, but also remove the semi-crystalline water generated during the transfer process of the anhydrous lithium iodide.

[0081] Comparative Example 3 uses spray drying instead of vacuum heating and drying, and the water content of the anhydrous lithium iodide product obtained is reduced, but it is still higher than that of the present application, indicating that spray drying still has a bottleneck in removing water from anhydrous lithium iodide.

[0082] Comparative Example 4 has no ceramic grinding balls, resulting in bubble holes on the surface of the lithium trihydrate iodide drying process, the moisture content is higher than the embodiment of the application and the discharge is difficult, and the structure needs to be manually damaged before the ball milling process.

[0083] Comparative Example 5 and Comparative Example 6 use different proportions of ceramic grinding balls, and too low a proportion will cause the material surface to be adhered in a small area, and too high a proportion will cause the material to sink to the bottom during the ball milling process, so that the particle size cannot be refined, and the moisture content decreases less during the open drying process, indicating that the solid-liquid ball milling ratio of the application is optimal.

[0084] Comparative Example 7 is vacuum drying instead of open drying to remove residual anhydrous ethanol. In the case of less material, the effect of vacuum drying is close to open drying, but in the process of enlarging the drying amount, vacuum drying causes the dehydration effect to be unsatisfactory due to the thickness of the material accumulation, while the embodiment of the application uses open stirring drying, which can effectively dehydrate the material in depth and give the lithium iodide product a lower water content.

[0085] The above is only a preferred embodiment of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for preparing anhydrous lithium iodide with low water content, characterized in that, The process involves adding ceramic grinding balls to a concentrated lithium iodide trihydrate solution and then vacuum heating and drying it to obtain anhydrous lithium iodide crude material. The anhydrous lithium iodide crude material is then ball-milled at a humidity of less than 2.0%, and finally dried in an open environment after ball milling to obtain the low-moisture anhydrous lithium iodide.

2. The preparation method according to claim 1, characterized in that, The ceramic grinding balls include alumina balls and / or zirconia balls; And / or, the liquid-to-solid ratio of the lithium iodide trihydrate concentrate to the ceramic grinding ball is 4~6:

1.

3. The preparation method according to claim 1 or 2, characterized in that, The vacuum heating and drying process includes a first stage and a second stage. The heating temperature of the first stage is 60~80℃ and the drying time is 4~6h. The heating temperature of the second stage is 260~300℃ and the drying time is 4~6h. And / or, the heating rate of the vacuum heating drying process is 1~3℃ / min, and the vacuum degree is ≤0.1bar; And / or, stirring is maintained during the vacuum heating and drying process, with the stirring speed at 15~25 rpm in the first stage and at 8~12 rpm in the second stage.

4. The preparation method according to claim 1, characterized in that, The ball milling includes dry ball milling or wet ball milling; And / or, the dry ball milling speed is 300~400 rpm and the ball milling time is 2~3 h; And / or, the ball milling process is carried out inside a glove box.

5. The preparation method according to claim 1, characterized in that, The open-air drying temperature is 100~120℃, the drying time is 1~2h, and the open-air drying is carried out in a glove box with an inert atmosphere. And / or, the open drying process is kept stirred at a speed of 20-40 rpm.

6. The preparation method according to claim 1, characterized in that, The lithium iodide trihydrate concentrate is obtained by heating and concentrating the reaction solution for synthesizing lithium iodide trihydrate, or by dissolving the prepared lithium iodide trihydrate and then heating and concentrating it. And / or, the heating concentration temperature is 100~150℃, and the time is 2~4h; an inert gas is used as a protective gas during the heating concentration process; And / or, during the heating and concentration process, stirring is maintained at a speed of 100~150 rpm.

7. The preparation method according to claim 6, characterized in that, The reaction solution for preparing the synthetic lithium iodide trihydrate comprises reacting hydroiodic acid with lithium hydroxide, wherein the hydroiodic acid contains I... - With the Li in the lithium hydroxide + The molar ratio is 1:0.8~1.

2.

8. The preparation method according to claim 6, characterized in that, The reaction solution for preparing synthetic lithium iodide trihydrate includes a mixture of elemental iodine, water, hydrazine, and lithium hydroxide, wherein the molar ratio of lithium hydroxide to iodine is 2:1.0~1.

3.

9. A low-moisture-content anhydrous lithium iodide, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the preparation method according to any one of claims 1 to 8 in the preparation of batteries or catalysts.

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