Preparation method of anhydrous lithium iodide and high-purity nanoscale anhydrous lithium iodide

Abstract

The invention discloses a preparation method of anhydrous lithium iodide and high-purity nanoscale anhydrous lithium iodide. The preparation method of the anhydrous lithium iodide provided by the invention comprises the following steps: taking a lithium iodide trihydrate solution as a raw material, performing dehydration pretreatment on the raw material by adopting a spray drying process or a vacuum freeze drying process to obtain an intermediate, and then performing dehydration treatment on the intermediate by adopting a vacuum drying process. According to the preparation method provided by the invention, the lithium iodide trihydrate solution is treated through a spray drying process or a vacuum freeze drying process to remove at least half bound water in the lithium iodide trihydrate to obtain the intermediate, and the process can avoid generation of a colloidal film on the surface of the lithium iodide, can form a pore structure for water evaporation, and is easy to break; and then carrying out vacuum drying treatment on the intermediate to thoroughly remove the residual bound water so as to obtain an anhydrous lithium iodide crude product. And carrying out wet ball milling treatment on the anhydrous iodized crude product to obtain the high-purity nanoscale anhydrous lithium iodide.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of anhydrous lithium iodide, in particular to a preparation method of anhydrous lithium iodide and high-purity nano-scale anhydrous lithium iodide. Background Art

[0002] Anhydrous lithium iodide is one of the important lithium compounds and is widely used in the fields of medicine, batteries, organic synthesis, functional materials, etc. In the field of medicine, anhydrous lithium iodide is one of the key raw materials for the synthesis of dopamine drugs, which have been used to treat Parkinson's disease. In the field of lithium batteries, anhydrous lithium iodide is widely used in lithium battery electrolytes. Lithium batteries using anhydrous lithium iodide as electrolyte have been used in pacemakers. They have the advantages of high energy, low loss, long life, good sealing performance, and the ability to prevent the influx of body fluids. In solid electrolytes, adding anhydrous lithium iodide can increase the conductivity of lithium ions and the stability of the battery. As the electrolyte of high-end lithium power batteries, the product quality of anhydrous lithium iodide determines the safety and reliability of lithium power batteries, and the water content and stability of the product have become one of the key factors affecting lithium power batteries.

[0003] At present, the preparation of anhydrous lithium iodide is mainly through the drying and dehydration of lithium iodide trihydrate, and there are several methods for preparing lithium iodide trihydrate. The first is the neutralization method: lithium hydroxide or lithium carbonate is used as a raw material to react with hydroiodic acid to prepare lithium iodide trihydrate, and then anhydrous lithium iodide is obtained through three-stage dehydration, which has poor color and a water content of >500ppm; the second is the hydrazine method: adding hydrazine aqueous solution and lithium hydroxide to the reaction equipment, and adding iodine in batches under stirring and cooling. The reaction solution is concentrated, cooled and crystallized to obtain lithium iodide trihydrate crystals, and then dried to obtain anhydrous lithium iodide, but the water content of lithium iodide obtained by this reaction is generally >200pm. The third is the solid phase method: using molten metal lithium and iodine at high temperature to carry out a synthesis reaction, and high-purity anhydrous lithium iodide can be prepared by purification. Although the water content can be obtained below 100ppm, it has high requirements for equipment and low yield, and large-scale production is difficult to achieve. The lithium iodide obtained by the above three process methods each has its own defects. The process conditions are harsh, and the lithium iodide dried under high temperature conditions is easy to deteriorate and decompose. The anhydrous lithium iodide produced has poor color, is easy to harden, has a low yield, and has a high water content (greater than 200ppm). Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for preparing anhydrous lithium iodide and high-purity nano-scale anhydrous lithium iodide.

[0005] The invention provides a method for preparing high-purity nanometer-level anhydrous lithium iodide, which comprises: using lithium iodide trihydrate solution as a raw material, carrying out dehydration pretreatment on the raw material by a spray drying process or a vacuum freeze drying process to obtain an intermediate, and then carrying out dehydration treatment on the intermediate by a vacuum drying process.

[0006] The present invention also provides a method for preparing high-purity nanometer-scale anhydrous lithium iodide, which comprises: using lithium iodide trihydrate solution as a raw material, performing a dehydration pretreatment on the raw material by a spray drying process or a vacuum freeze drying process to obtain an intermediate, then performing a dehydration treatment on the intermediate by a vacuum drying process to obtain an anhydrous lithium iodide crude product, and then performing a wet ball milling process to grind and purify the anhydrous lithium iodide crude product to obtain high-purity nanometer-scale anhydrous lithium iodide.

[0007] The present invention also provides high-purity nanometer-level anhydrous lithium iodide prepared by the above-mentioned preparation method.

[0008] The present invention has the following beneficial effects:

[0009] The present invention provides a method for preparing anhydrous lithium iodide and high-purity nano-scale anhydrous lithium iodide. The method for preparing anhydrous lithium iodide comprises: using lithium iodide trihydrate solution as raw material, performing dehydration pretreatment on the raw material by a spray drying process or a vacuum freeze drying process to obtain an intermediate, and then performing dehydration treatment on the intermediate by a vacuum drying process. The above-mentioned preparation method, performing dehydration pretreatment of the lithium iodide trihydrate solution by spray drying or vacuum freeze drying to obtain an intermediate LiI·xH2O (x≤1.5), can not only avoid the problem of difficult discharge caused by the formation of a colloidal film on the surface of lithium iodide by direct vacuum drying, but also can form a pore structure for water evaporation, which is easy to break; the intermediate is subjected to vacuum drying to remove the remaining water, and anhydrous lithium iodide can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0011] Figure 1 This is a flow chart for the preparation of high-purity nano-scale anhydrous lithium iodide. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0013] The following is a detailed description of a method for preparing anhydrous lithium iodide and high-purity nano-scale anhydrous lithium iodide provided in an embodiment of the present invention.

[0014] In a first aspect, an embodiment of the present invention provides a method for preparing anhydrous lithium iodide, which comprises: using lithium iodide trihydrate solution as a raw material, using a spray drying process or a vacuum freeze drying process to dehydrate the raw material to obtain an intermediate, and then using a vacuum drying process to dehydrate the intermediate.

[0015] The inventors have found through practice that in the dehydration and drying process of lithium iodide trihydrate, the reason why it is difficult to dehydrate lithium iodide trihydrate, especially the dehydration of bound water, is that direct vacuum drying for dehydration will form a colloidal film on the surface of lithium iodide, which not only makes it difficult to discharge the material, but also makes it difficult to remove the bound water inside due to the constraint of the surface colloidal film.

[0016] The embodiment of the present invention provides a method for preparing anhydrous lithium iodide, which comprises: performing dehydration pretreatment on a lithium iodide trihydrate solution by spray drying or vacuum freeze drying. The process can effectively avoid the problem of difficulty in discharging caused by the formation of a gelatinous film on the surface of lithium iodide in the direct vacuum heating drying process, and can form a pore structure for water evaporation, which is easy to break. After vacuum drying treatment, anhydrous lithium iodide with extremely low water content can be obtained.

[0017] In an optional embodiment, the temperature of the spray drying process is 100-150° C. and the time is 1-2 hours.

[0018] In an optional embodiment, the temperature of the vacuum freeze-drying process is -40 to -60 degrees Celsius, and the time is 4 to 6 hours.

[0019] The embodiment of the present invention provides a method for preparing anhydrous lithium iodide, which comprises: performing dehydration pretreatment on a lithium iodide trihydrate solution through a spray drying process or a vacuum freeze drying process, and controlling the appropriate temperature and time of the dehydration pretreatment to remove at least half of the bound water in the lithium iodide trihydrate to obtain an intermediate LiI·xH2O, where x≤1.5. In addition, the process can effectively avoid the problem of difficult discharge caused by the formation of a colloidal film on the surface of the lithium iodide during direct vacuum drying, and can also form a pore structure for water evaporation, which is easy to break and is conducive to subsequent further drying and dehydration.

[0020] In an optional embodiment, the vacuum drying equipment in the vacuum drying process is a titanium vacuum rake dryer;

[0021] Preferably, the vacuum drying process includes three stages of drying and dehydration treatment, wherein: the first stage drying and dehydration temperature is 60-80°C, the time is 1-2h, the second stage drying and dehydration temperature is 150-180°C, the time is 2-4h, the third stage drying and dehydration temperature is 260-300°C, the time is 4-6h, and the whole drying and dehydration process is carried out in a glove box.

[0022] The embodiment of the present invention provides a method for preparing anhydrous lithium iodide. In the vacuum drying process, a titanium vacuum rake dryer is used, which can effectively avoid the corrosion of metal materials by hydrazine hydrate and the like, and at the same time, avoid the problem that lithium iodide is easily decomposed when exposed to light. In addition, in addition to controlling the drying and dehydration environment to be water-free and oxygen-free, segmented vacuum heating can accurately control the temperature, improve the heating efficiency and improve the product yield. The dehydration temperature of the three stages is determined based on the dehydration weight loss temperature of lithium iodide trihydrate, so the bound water remaining after spray drying can be effectively removed.

[0023] In a second aspect, an embodiment of the present invention further provides a method for preparing high-purity nano-scale anhydrous lithium iodide, which comprises: using lithium iodide trihydrate solution as a raw material, performing a spray drying process or a vacuum freeze drying process to dehydrate the raw material to obtain an intermediate, then performing a vacuum drying process to dehydrate the intermediate to obtain a crude anhydrous lithium iodide product, and then performing a wet ball milling process to grind and purify the crude anhydrous lithium iodide product to obtain high-purity nano-scale anhydrous lithium iodide.

[0024] In an optional embodiment, the medium of the wet ball milling process is anhydrous ethanol;

[0025] Preferably, the wet ball milling speed is 400-600 rpm and the time is 4-6 hours.

[0026] The embodiment of the present invention provides a method for preparing high-purity nanometer-level anhydrous lithium iodide, which comprises: subjecting a crude anhydrous lithium iodide obtained by dehydration to a wet ball milling process, using anhydrous ethanol as a wet ball milling medium, ball milling can reduce the particle size of the anhydrous lithium iodide, and at the same time, impurities and water therein can be dissolved in the anhydrous ethanol, and the anhydrous lithium iodide is impurity-removed, so that a low particle size can be ensured, secondary impurity removal is achieved, and water content is reduced.

[0027] In an optional embodiment, the lithium iodide trihydrate solution is prepared by the following steps: mixing diluted hydrazine hydrate with elemental iodine and lithium hydroxide to react to obtain a dilute lithium iodide trihydrate solution;

[0028] Preferably, the preparation of the dilute lithium iodide trihydrate solution comprises: adding diluted hydrazine hydrate dropwise to a mixed solution of elemental iodine and lithium hydroxide to react, and stopping adding the diluted hydrazine hydrate dropwise after the mixed solution changes from dark purple to colorless, to obtain a dilute lithium iodide trihydrate solution;

[0029] Preferably, the mass fraction of the diluted hydrazine hydrate is 15wt% to 25wt%, the molar ratio of lithium hydroxide to iodine in the mixed solution is 2:1.0 to 1.3, and the solid-liquid ratio is 1:2 to 3;

[0030] Preferably, the method further comprises: concentrating the dilute lithium iodide trihydrate solution to obtain a concentrated lithium iodide trihydrate solution, wherein: the heating and concentrating temperature is 100-150° C., and the time is 2-4 hours.

[0031] The embodiment of the present invention provides a method for preparing high-purity nanometer-scale anhydrous lithium iodide. In the process of preparing lithium iodide trihydrate solution by hydrazine method, diluted hydrazine hydrate, i.e. low-concentration hydrazine hydrate, is used, which can not only effectively control the reaction rate, but also reduce the heat generated in the reaction process, improve the safety of the reaction, and control the particle size of lithium iodide to obtain nanometer-scale regular and uniform lithium iodide trihydrate. The dilute lithium iodide trihydrate solution is subjected to a heating and concentration process to remove free water and a very small amount of bound water in the lithium iodide trihydrate.

[0032] In an optional embodiment, during the entire process of preparing the dilute lithium iodide trihydrate solution and heating and concentrating the solution, a protective gas is introduced and stirring is turned on, the protective gas is one of nitrogen and argon, and the stirring rate is 100-150 rpm.

[0033] In a third aspect, an embodiment of the present invention further provides a high-purity nano-scale anhydrous lithium iodide prepared by the above-mentioned preparation method.

[0034] In an optional embodiment, the purity of the high-purity nano-scale anhydrous lithium iodide product is greater than 99.9%, the water content is less than 150ppm, and the particle size is 180-300nm. The anhydrous lithium iodide product prepared by the scheme provided by the present invention has a purity of more than 99.9% and a water content of less than 150ppm, which is a breakthrough compared with the anhydrous lithium iodide product sold on the market at present, which has a water content of more than 500ppm. The process is simple, safe and effective, and is suitable for industrial production.

[0035] The present invention will be further described below in conjunction with the embodiments.

[0036] A method for preparing high-purity nanometer-level anhydrous lithium iodide, see Figure 1 , including the following steps:

[0037] a. Preparation of concentrated solution of lithium iodide trihydrate: lithium iodide trihydrate is prepared by hydrazine method, and the raw materials are lithium source such as lithium carbonate or lithium hydroxide, hydrazine hydrate and elemental iodine; wherein the molar ratio of the added amount of lithium hydroxide to iodine is 2:1.0-1.3, and then pure water is added to the container containing the lithium source and iodine, and the solid-liquid ratio is 1:2-3, and finally the diluted hydrazine hydrate is added by dropwise addition, and the mass fraction of the diluted hydrazine hydrate is 15wt%-25wt%, and the dropwise addition of the diluted hydrazine hydrate is stopped after the mixed solution changes from dark purple to anhydrous, and the solution after the reaction is heated and concentrated to obtain a concentrated solution of lithium iodide trihydrate, and the heating and concentration temperature is 100-150°C, and the heating time is 2-4h. Protective gas is passed through the whole process, and the protective gas is one of nitrogen and argon. Stirring is started throughout the whole process, and the stirring parameter is 100-150rpm;

[0038] b. Spray drying: The concentrated solution of lithium iodide trihydrate obtained in process a is spray dried to obtain the intermediate LiI·xH2O (x≤1.5), wherein the spray drying temperature is 100-150°C.

[0039] c. Vacuum heating and drying: the intermediate LiI·xH2O (x≤1.5) obtained in process b is dehydrated to prepare anhydrous lithium iodide; the drying equipment is a titanium vacuum rake dryer, and the drying parameters are: the first stage dehydration temperature is 60-80°C, drying 1-2h, the second stage dehydration temperature is 150-180°C, 2-4h, and the third stage dehydration temperature is 260-300°C, 4-6h. The process is completed in a glove box.

[0040] d. Wet ball milling: The block anhydrous lithium iodide obtained in process c is subjected to wet ball milling, the solvent is anhydrous ethanol, the ball milling parameters are 400-600 rpm, and the ball milling wet anhydrous lithium iodide is vacuum dried to obtain high-purity nano-scale anhydrous lithium iodide;

[0041] Preferably, in step a, the molar ratio of lithium hydroxide to iodine added is 2:1.1, the solid-liquid ratio is 1:2, the mass fraction of hydrazine hydrate is 20wt%, the heating concentration temperature is 120°C, the heating time is 3h, and the stirring speed is 120rpm;

[0042] Preferably, in step b, the spray drying temperature is 130° C., and the molecular formula of the intermediate obtained by spray drying is LiI·xH2O (x=0.8);

[0043] Preferably, in step c, the drying parameters are: first stage dehydration temperature 70°C, drying time 1h, second stage dehydration temperature 160°C, time 3h, third stage dehydration temperature 280°C, time 5h;

[0044] Preferably, in step d, the ball milling parameters are 500 rpm, 6 h.

[0045] Example 1

[0046] A method for preparing high-purity nano-scale anhydrous lithium iodide comprises the following steps:

[0047] (1) preparing a concentrated solution of lithium iodide trihydrate: the raw materials are lithium hydroxide, hydrazine hydrate and elemental iodine; wherein the molar ratio of the added amount of lithium hydroxide to iodine is 2:1.1, then pure water is added to a container containing a lithium source and iodine, with a solid-liquid ratio of 1:2, and finally diluted hydrazine hydrate is added by dropwise addition, wherein the mass fraction of the diluted hydrazine hydrate is 20wt%, and the addition of low-concentration hydrazine hydrate is stopped after the mixed solution changes from dark purple to anhydrous, and the solution after the reaction is heated and concentrated to obtain a concentrated solution of lithium iodide trihydrate, and the heating concentration temperature is 120°C, and the heating is performed for 3 hours, and a protective gas is passed throughout the process, and the protective gas is one of nitrogen and argon. Stirring is started throughout the process, and the stirring parameter is 120rpm;

[0048] (2) Spray drying: The concentrated solution of lithium iodide trihydrate obtained in step (1) is spray dried to obtain the intermediate LiI·xH2O (x=0.8), wherein the spray drying temperature is 130°C.

[0049] (3) Vacuum drying: The intermediate LiI·xH2O (x=0.8) obtained in step (2) is dehydrated to prepare anhydrous lithium iodide; the drying equipment is a titanium vacuum rake dryer, and the drying parameters are as follows: the first stage dehydration temperature is 70°C, drying for 1 h, the second stage dehydration temperature is 160°C, drying for 3 h, and the third stage dehydration temperature is 280°C, drying for 5 h. The process is completed in a glove box.

[0050] (4) Wet ball milling: The block of anhydrous lithium iodide obtained in step (3) is wet ball milled, the solvent is anhydrous ethanol, the ball milling parameters are 500 rpm, and the milling time is 6 hours. The wet anhydrous lithium iodide after ball milling is vacuum dried. The obtained anhydrous lithium iodide sample is numbered LiI-1.

[0051] Example 2

[0052] A method for preparing high-purity nano-scale anhydrous lithium iodide comprises the following steps:

[0053] (1) preparing a concentrated solution of lithium iodide trihydrate: the raw materials are lithium hydroxide, hydrazine hydrate and elemental iodine; wherein the molar ratio of the added amount of lithium hydroxide to iodine is 2:1.0, then pure water is added to a container containing a lithium source and iodine, with a solid-liquid ratio of 1:2, and finally diluted hydrazine hydrate is added by dropwise addition, wherein the mass fraction of the diluted hydrazine hydrate is 15wt%, and the addition of low-concentration hydrazine hydrate is stopped after the mixed solution changes from dark purple to anhydrous, and the solution after the reaction is heated and concentrated to obtain a concentrated solution of lithium iodide trihydrate, and the heating concentration temperature is 100°C, and the heating is performed for 5 hours, and a protective gas is passed throughout the process, and the protective gas is one of nitrogen and argon. Stirring is started throughout the process, and the stirring parameter is 120rpm;

[0054] 2) Spray drying: spray drying the concentrated solution of lithium iodide trihydrate obtained in step (1) to obtain the intermediate LiI·xH2O (x=1.5), wherein the spray drying temperature is 100°C.

[0055] (3) Vacuum drying: The intermediate LiI·xH2O (x=1.5) obtained in step (2) is dehydrated to prepare anhydrous lithium iodide; the drying equipment is a titanium vacuum rake dryer, and the drying parameters are as follows: the first stage dehydration temperature is 70°C, drying for 1 h, the second stage dehydration temperature is 160°C, drying for 3 h, and the third stage dehydration temperature is 280°C, drying for 5 h. The process is completed in a glove box.

[0056] (4) Wet ball milling: The block of anhydrous lithium iodide obtained in step (3) is wet ball milled, the solvent is anhydrous ethanol, the ball milling parameters are 500 rpm, and the milling time is 6 hours. The wet anhydrous lithium iodide after ball milling is vacuum dried. The obtained anhydrous lithium iodide sample is numbered LiI-2.

[0057] Example 3

[0058] A method for preparing high-purity nano-scale anhydrous lithium iodide comprises the following steps:

[0059] (1) preparing a concentrated solution of lithium iodide trihydrate: the raw materials are lithium hydroxide, hydrazine hydrate and elemental iodine; wherein the molar ratio of the added amount of lithium hydroxide to iodine is 2:1.3, then pure water is added to a container containing a lithium source and iodine, with a solid-liquid ratio of 1:3, and finally diluted hydrazine hydrate is added by dropwise addition, wherein the mass fraction of the diluted hydrazine hydrate is 25wt%, and the addition of low-concentration hydrazine hydrate is stopped after the mixed solution changes from dark purple to anhydrous, and the solution after the reaction is heated and concentrated to obtain a concentrated solution of lithium iodide trihydrate, and the heating concentration temperature is 120°C, and the heating is performed for 3 hours, and a protective gas is passed throughout the process, and the protective gas is one of nitrogen and argon. Stirring is started throughout the process, and the stirring parameter is 120rpm;

[0060] (2) Spray drying: The concentrated solution of lithium iodide trihydrate obtained in step (1) is spray dried to obtain the intermediate LiI·xH2O (x=1.0), wherein the spray drying temperature is 150°C.

[0061] Steps (3) and (4) are consistent with those in Example 1, and the obtained anhydrous lithium iodide sample is numbered LiI-3.

[0062] Example 4

[0063] A method for preparing high-purity nanometer-level anhydrous lithium iodide, which differs from Example 1 only in that, in step (3) of vacuum drying, the drying parameters are a first-stage dehydration temperature of 60° C., drying for 2 h, a second-stage dehydration temperature of 150° C., 4 h, and a third-stage dehydration temperature of 260° C., 6 h, and the process is completed in a glove box. The obtained anhydrous lithium iodide sample is numbered LiI-4.

[0064] Example 5

[0065] A method for preparing high-purity nanometer-level anhydrous lithium iodide, which differs from Example 1 only in that, in step (3) of vacuum drying, the drying parameters are: a first-stage dehydration temperature of 80° C., drying for 1 h, a second-stage dehydration temperature of 180° C., drying for 2 h, and a third-stage dehydration temperature of 300° C., drying for 4 h, and the process is completed in a glove box. The obtained anhydrous lithium iodide sample is numbered LiI-5.

[0066] Example 6

[0067] A method for preparing high-purity nano-scale anhydrous lithium iodide, which differs from Example 1 only in that step (4) wet ball milling: the ball milling parameters are 600 rpm, 6 h, and the obtained anhydrous lithium iodide sample is numbered LiI-6.

[0068] Example 7 (removal of the first molecule of water, vacuum freeze drying)

[0069] A method for preparing high-purity nano-scale anhydrous lithium iodide, which differs from Example 1 only in that step (2) is vacuum freeze-drying, the drying parameters are -50°C, 12h, and the obtained anhydrous lithium iodide sample is numbered LiI-7.

[0070] Comparative Example 1

[0071] A method for preparing high-purity nano-scale anhydrous lithium iodide, which differs from Example 1 only in that in step (2), the spray drying temperature is 80°C, the intermediate LiI·xH2O (x=2.5), and the obtained anhydrous lithium iodide sample is numbered LiI-8.

[0072] Comparative Example 2

[0073] A method for preparing high-purity nanometer-level anhydrous lithium iodide, which differs from Example 1 only in that, in step (3), the drying parameters are a first-stage dehydration temperature of 70°C, drying for 1 hour, a second-stage dehydration temperature of 160°C, 3 hours, and a third-stage dehydration temperature of 280°C, 5 hours, and the process is completed in a fume hood. The obtained anhydrous lithium iodide sample is numbered LiI-9.

[0074] Comparative Example 3

[0075] A method for preparing high-purity nano-scale anhydrous lithium iodide, which differs from Example 1 only in that, in step (3), the drying parameters are a first-stage dehydration temperature of 70° C., drying for 1 h, a second-stage dehydration temperature of 160° C., drying for 3 h, and a third-stage dehydration temperature of 250° C., drying for 6 h. The process is completed in a glove box, and the obtained anhydrous lithium iodide sample is numbered LiI-10.

[0076] Comparative Example 4

[0077] A method for preparing high-purity nano-scale anhydrous lithium iodide is disclosed, which differs from Example 1 only in that, in step (4), dry ball milling is used instead, and the obtained anhydrous lithium iodide sample is numbered LiI-11.

[0078] Comparative Example 5

[0079] A method for preparing anhydrous lithium iodide is disclosed. The anhydrous lithium iodide is prepared by the method of CN 110759363 A. The obtained anhydrous lithium iodide sample is numbered LiI-12.

[0080] Comparative Example 6

[0081] A method for preparing anhydrous lithium iodide is similar to the steps of Example 1, except that the drying process is only spray drying. The obtained anhydrous lithium iodide sample is numbered LiI-13.

[0082] Comparative Example 7

[0083] A method for preparing anhydrous lithium iodide is similar to the steps of Example 1, except that the temperature of the three-stage vacuum drying dehydration is 320° C. The obtained anhydrous lithium iodide sample is numbered LiI-14.

[0084] The composition parameters of the anhydrous lithium iodide samples prepared in Examples 1-7 and Comparative Examples 1-7 are shown in Table 1.

[0085] Table 1

[0086]

[0087] It can be seen from Table 1 above that the purity of the high-purity nano-scale anhydrous lithium iodide product prepared by the solution provided in the embodiment of the present invention is greater than 99.9%, the water content is less than 150ppm, and the particle size is 180-300nm. The performance of the anhydrous lithium iodide product obtained by changing the experimental conditions deteriorates, such as high water content (greater than 200ppm), larger particle size, reduced purity or product discoloration (such as the anhydrous lithium iodide obtained in Comparative Example 7, the temperature is too high to cause the lithium iodide to decompose and produce iodine, resulting in a purple product color).

[0088] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing anhydrous lithium iodide, characterized in that: It includes: Lithium iodide trihydrate solution is used as a raw material, a spray drying process or a vacuum freeze drying process is used to perform a dehydration pretreatment on the raw material to obtain an intermediate, and then a vacuum drying process is used to perform a dehydration treatment on the intermediate.

2. The preparation method according to claim 1, characterized in that: The temperature of the spray drying process is 100-150° C. and the time is 1-2 hours.

3. The preparation method according to claim 1, characterized in that: The temperature of the vacuum freeze-drying process is -40 to -60 degrees Celsius, and the time is 4 to 6 hours.

4. The preparation method according to claim 1, characterized in that: The vacuum drying equipment in the vacuum drying process is a titanium vacuum rake dryer; Preferably, the vacuum drying process includes three stages of drying and dehydration treatment, wherein: the first stage drying and dehydration temperature is 60-80°C, the time is 1-2h, the second stage drying and dehydration temperature is 150-180°C, the time is 2-4h, the third stage drying and dehydration temperature is 260-300°C, the time is 4-6h, and the whole drying and dehydration process is carried out in a glove box.

5. A method for preparing high-purity nano-scale anhydrous lithium iodide, characterized in that: It includes: Lithium iodide trihydrate solution is used as a raw material, and a spray drying process or a vacuum freeze drying process is used to dehydrate the raw material to obtain an intermediate, and then a vacuum drying process is used to dehydrate the intermediate to obtain an anhydrous lithium iodide crude product, and then a wet ball milling process is used to grind and purify the anhydrous lithium iodide crude product to obtain high-purity nano-scale anhydrous lithium iodide.

6. The preparation method according to claim 5, characterized in that: The medium of the wet ball milling process is anhydrous ethanol; Preferably, the wet ball milling speed is 400-600 rpm and the time is 4-6 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that The lithium iodide trihydrate solution is prepared by the following steps: mixing diluted hydrazine hydrate with elemental iodine and lithium hydroxide to react to obtain a dilute lithium iodide trihydrate solution; Preferably, the preparation of the dilute lithium iodide trihydrate solution comprises: adding diluted hydrazine hydrate dropwise to a mixed solution of elemental iodine and lithium hydroxide to react, and stopping adding the diluted hydrazine hydrate dropwise after the mixed solution changes from dark purple to colorless, to obtain a dilute lithium iodide trihydrate solution; Preferably, the mass fraction of the diluted hydrazine hydrate is 15wt% to 25wt%, the molar ratio of lithium hydroxide to iodine in the mixed solution is 2:1.0 to 1.3, and the solid-liquid ratio is 1:2 to 3; Preferably, the method further comprises: concentrating the dilute lithium iodide trihydrate solution to obtain a concentrated lithium iodide trihydrate solution, wherein: the heating and concentrating temperature is 100-150° C., and the time is 2-4 hours.

8. The preparation method according to claim 7, characterized in that: During the whole process of the preparation process and the heating and concentration process of the lithium iodide trihydrate dilute solution, a protective gas is introduced and stirring is started. The protective gas is one of nitrogen and argon, and the stirring rate is 100-150 rpm.

9. High-purity nano-scale anhydrous lithium iodide obtained by the preparation method according to any one of claims 5 to 7.

10. The high-purity nano-scale anhydrous lithium iodide according to claim 9, characterized in that: The purity of the high-purity nanometer-level anhydrous lithium iodide product is greater than 99.9%, the water content is less than 150 ppm, and the particle size is 180-300 nm.

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