A kind of preparation method of lithium tetrachloroaluminate

Abstract

The present invention belongs to the technical field of battery materials, and provides a method for preparing lithium tetrachloroaluminate. The preparation method of the present invention comprises mixing anhydrous lithium chloride, anhydrous aluminum chloride, an additive and a solvent, heating and refluxing, and filtering to obtain a hot filtrate; cooling and crystallizing the hot filtrate to obtain lithium tetrachloroaluminate. The present invention is based on the preparation of lithium tetrachloroaluminate by an organic phase dissolution method, and by selecting a specific aluminum-containing compound as an additive, the occurrence of side reactions is effectively controlled, and at the same time, the influence of impurities and moisture contained in the raw materials on the yield and product quality of lithium tetrachloroaluminate is reduced, thereby avoiding the blackening and graying of lithium tetrachloroaluminate, and improving the appearance quality and purity of lithium tetrachloroaluminate; the preparation process of the present invention is simple, the equipment investment is small, the production cost is low, and it is safe and reliable, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of battery materials, and in particular to a method for preparing lithium tetrachloroaluminate. Background Art

[0002] Lithium thionyl chloride battery is a lithium battery with a relatively high specific capacity, and lithium tetrachloroaluminate is an essential electrolyte in lithium thionyl chloride battery. The preparation method and process optimization of lithium tetrachloroaluminate (LiAlCl4) are of great significance to the battery industry.

[0003] At present, the preparation methods of lithium tetrachloroaluminate mainly include direct melting method and organic phase dissolution method. The direct melting method is to mix anhydrous lithium chloride and anhydrous aluminum chloride in equal proportions, and cool to obtain lithium tetrachloroaluminate after melting reaction at high temperature. This method has high requirements for raw materials and equipment, and the obtained lithium tetrachloroaluminate is in block form, which needs to be further processed into powder before it can be used, and is not suitable for large-scale production. The organic phase dissolution method utilizes the characteristic that lithium tetrachloroaluminate has a considerable solubility difference in non-polar solvents with temperature changes, dissolves anhydrous lithium chloride and anhydrous aluminum chloride with non-polar solvents at a certain temperature, and obtains crystalline lithium tetrachloroaluminate by cooling crystallization and separation and drying. Both of the above methods require pre-treatment of raw materials lithium chloride and aluminum chloride, such as drying anhydrous lithium chloride, sublimation purification of anhydrous aluminum chloride, etc., which increases the complexity of the process flow and improves production costs. In addition, the organic phase dissolution method also requires the addition of a certain amount of aluminum powder, which is flammable and explosive, and is not conducive to safe production. In addition, the lithium tetrachloroaluminate produced by this method is severely stained, black and gray, affecting the appearance and quality of the product.

[0004] Therefore, it is of great prospect to develop a method for preparing lithium tetrachloroaluminate with simple process flow, low equipment investment, low production cost, safety and reliability, and no dyeing of the product and high purity. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing lithium tetrachloroaluminate in view of the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing lithium tetrachloroaluminate, comprising the following steps:

[0008] 1) mixing anhydrous lithium chloride, anhydrous aluminum chloride, an additive and a solvent, heating and refluxing, and then filtering to obtain a hot filtrate;

[0009] 2) Cooling the hot filtrate for crystallization to obtain lithium tetrachloroaluminate.

[0010] Preferably, the additive in step 1) comprises one or more of aluminum oxide, aluminum hydroxide, aluminum sulfate and aluminum nitrate.

[0011] Preferably, the solvent in step 1) comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

[0012] Preferably, in step 1), the molar ratio of anhydrous lithium chloride to anhydrous aluminum chloride is 1-1.1:1, the molar ratio of anhydrous lithium chloride to the additive is 100:1-10, and the molar volume ratio of anhydrous aluminum chloride to the solvent is 1 mol:300-400 mL.

[0013] Preferably, the temperature of the heating reflux in step 1) is 60-100° C., and the heating reflux time is 30-60 min.

[0014] Preferably, the filtration temperature in step 1) is 60-100°C.

[0015] Preferably, in step 2), stirring is performed during the cooling crystallization process, and the stirring speed is 100-300 rpm; and the cooling crystallization is stopped when the temperature reaches 10-20°C.

[0016] Preferably, after the cooling crystallization in step 2) is completed, filtering, washing and drying are performed in sequence to obtain lithium tetrachloroaluminate.

[0017] Preferably, the solvent used for the washing comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

[0018] Preferably, the drying is vacuum drying, the vacuum drying temperature is 30 to 60° C., the vacuum degree of the vacuum drying is -0.3 to -0.1 MPa, and the vacuum drying time is 3 to 5 hours.

[0019] Beneficial effects of the present invention:

[0020] The invention is based on the preparation of lithium tetrachloroaluminate by an organic phase dissolution method. By selecting a specific aluminum-containing compound as an additive, the occurrence of side reactions is effectively controlled, and the influence of impurities and moisture contained in the raw materials on the yield and product quality of lithium tetrachloroaluminate is reduced, thereby avoiding the blackening and graying of lithium tetrachloroaluminate and improving the appearance quality and purity of lithium tetrachloroaluminate. The preparation process of the invention is simple, the equipment investment is small, the production cost is low, and it is safe and reliable, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of the method for preparing lithium tetrachloroaluminate. DETAILED DESCRIPTION

[0022] The present invention provides a method for preparing lithium tetrachloroaluminate, comprising the following steps:

[0023] 1) mixing anhydrous lithium chloride, anhydrous aluminum chloride, an additive and a solvent, heating and refluxing, and then filtering to obtain a hot filtrate;

[0024] 2) Cooling the hot filtrate for crystallization to obtain lithium tetrachloroaluminate.

[0025] In the present invention, the additive in step 1) preferably comprises one or more of aluminum oxide, aluminum hydroxide, aluminum sulfate and aluminum nitrate.

[0026] In the present invention, the solvent in step 1) preferably comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

[0027] In the present invention, the molar ratio of the anhydrous lithium chloride and the anhydrous aluminum chloride in step 1) is preferably 1-1.1:1, more preferably 1.01-1.08:1, and more preferably 1.05:1; the molar ratio of the anhydrous lithium chloride and the additive is preferably 100:1-10, more preferably 100:1.9-8, and more preferably 100:2.97-6; the molar volume ratio of the anhydrous aluminum chloride and the solvent is preferably 1 mol:300-400 mL, more preferably 1 mol:320-380 mL, and more preferably 1 mol:350 mL.

[0028] In the present invention, the temperature of the heating reflux in step 1) is preferably 60-100°C, more preferably 70-90°C, and more preferably 80°C; the time of heating reflux is preferably 30-60 min, more preferably 40-50 min, and more preferably 45 min.

[0029] In the present invention, the filtration temperature in step 1) is preferably 60-100°C, more preferably 70-90°C, and more preferably 80°C.

[0030] In the present invention, the purpose of the filtration in step 1) is to remove excess anhydrous lithium chloride and additives.

[0031] In the present invention, stirring is preferably performed during the cooling crystallization in step 2), and the stirring speed is preferably 100-300 rpm, more preferably 150-250 rpm, and more preferably 200 rpm; the cooling crystallization is preferably stopped when the temperature is 10-20°C.

[0032] In the present invention, after the cooling crystallization in step 2) is completed, it is preferred to filter, wash and dry in sequence to obtain lithium tetrachloroaluminate.

[0033] In the present invention, the solvent used for washing preferably comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

[0034] In the present invention, the filtrate obtained by filtration after the cooling crystallization in step 2) and the washing liquid obtained by washing can be returned to step 1) and heated to reflux together with the solvent in step 1).

[0035] In the present invention, the drying is preferably vacuum drying, and the temperature of vacuum drying is preferably 30 to 60°C, more preferably 35 to 55°C, and more preferably 40 to 50°C; the vacuum degree of vacuum drying is preferably -0.3 to -0.1 MPa, and more preferably -0.2 MPa; the time of vacuum drying is preferably 3 to 5 h, more preferably 3.5 to 4.5 h, and more preferably 4 h.

[0036] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0037] Example 1

[0038] Mix 350mL of cyclohexane, 1.01mol of anhydrous lithium chloride, 1mol of anhydrous aluminum chloride and 0.03mol of aluminum hydroxide and place them in a reaction flask. Heat the reaction flask to 70°C and reflux for 40min to obtain a reaction solution. Preheat the filter to 70°C, filter the reaction solution while hot to obtain a hot filtrate. Stir and cool the hot filtrate at a speed of 200rpm to crystallize. When the temperature is cooled to 20°C, crystals are precipitated to obtain a crystallization solution. Under a dry environment, the obtained crystallization solution is filtered to obtain a filter residue and a filtrate. The filter residue is washed with 175mL of toluene to obtain lithium tetrachloroaluminate crystals, and the filtrate and washing liquid are recovered at the same time. The lithium tetrachloroaluminate crystals are placed at 60°C and -0.1MPa and dried for 4h to obtain lithium tetrachloroaluminate.

[0039] The lithium tetrachloroaluminate prepared in this example has a white appearance, a yield of 78%, and a purity of 98%.

[0040] Example 2

[0041] Mix 175mL cyclohexane, 175mL dichloromethane, 1.05mol anhydrous lithium chloride, 1mol anhydrous aluminum chloride and 0.03mol aluminum nitrate and place them in a reaction flask. Heat the reaction flask to 60°C and reflux for 1h to obtain a reaction solution. Preheat the filter to 60°C, filter the reaction solution while hot to obtain a hot filtrate. Stir and cool the hot filtrate at a speed of 100rpm to crystallize. When the temperature is cooled to 20°C, crystals are precipitated to obtain a crystallization solution. Under a dry environment, the obtained crystallization solution is filtered to obtain a filter residue and a filtrate. The filter residue is washed with 175mL xylene to obtain lithium tetrachloroaluminate crystals, and the filtrate and washing liquid are recovered at the same time. The lithium tetrachloroaluminate crystals are placed at 60°C and -0.3MPa and dried for 4h to obtain lithium tetrachloroaluminate.

[0042] The lithium tetrachloroaluminate prepared in this example has a white appearance, a yield of 80%, and a purity of 99%.

[0043] Example 3

[0044] 175 mL of toluene, 175 mL of xylene, 1.05 mol of anhydrous lithium chloride, 1 mol of anhydrous aluminum chloride, 0.01 mol of aluminum sulfate and 0.01 mol of aluminum oxide were mixed and placed in a reaction flask. The reaction flask was heated to 100 ° C and refluxed for 1 hour to obtain a reaction solution. The filter device was preheated to 100 ° C, and the reaction solution was filtered while hot to obtain a hot filtrate. The hot filtrate was stirred and cooled at a speed of 300 rpm for crystallization. When the temperature was cooled to 20 ° C, crystals were precipitated to obtain a crystallization solution. Under a dry environment, the obtained crystallization solution was filtered to obtain a filter residue and a filtrate. The filter residue was washed with 175 mL of a mixed solvent of cyclohexane and dichloromethane (the volume ratio of cyclohexane and dichloromethane in the mixed solvent was 1:1) to obtain lithium tetrachloroaluminate crystals, and the filtrate and washing liquid were recovered at the same time. The lithium tetrachloroaluminate crystals were placed at 30 ° C and -0.2 MPa and dried for 4 hours to obtain lithium tetrachloroaluminate.

[0045] The lithium tetrachloroaluminate prepared in this example has a white appearance, a yield of 87%, and a purity of 99%.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing lithium tetrachloroaluminate, characterized in that: The following steps are included: 1) mixing anhydrous lithium chloride, anhydrous aluminum chloride, an additive and a solvent, heating and refluxing, and then filtering to obtain a hot filtrate; 2) Cooling the hot filtrate for crystallization to obtain lithium tetrachloroaluminate.

2. The preparation method according to claim 1, characterized in that: In step 1), the additive comprises one or more of aluminum oxide, aluminum hydroxide, aluminum sulfate and aluminum nitrate.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the solvent comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

4. The preparation method according to claim 3, characterized in that: Step 1) The molar ratio of anhydrous lithium chloride to anhydrous aluminum chloride is 1-1.1:1, the molar ratio of anhydrous lithium chloride to additive is 100:1-10, and the molar volume ratio of anhydrous aluminum chloride to solvent is 1 mol:300-400 mL.

5. The preparation method according to claim 4, characterized in that: The temperature of the heating reflux in step 1) is 60 to 100° C., and the time of the heating reflux is 30 to 60 minutes.

6. The preparation method according to claim 4 or 5, characterized in that: The filtration temperature in step 1) is 60-100°C.

7. The preparation method according to claim 6, characterized in that: Step 2) Stirring is performed during the cooling crystallization process, and the stirring speed is 100-300 rpm; and the cooling crystallization is stopped when the temperature reaches 10-20°C.

8. The preparation method according to claim 7, characterized in that: Step 2) After the cooling crystallization is completed, filtering, washing and drying are performed in sequence to obtain lithium tetrachloroaluminate.

9. The preparation method according to claim 8, characterized in that: The solvent used for the washing comprises one or more of cyclohexane, dichloromethane, toluene and xylene.

10. The preparation method according to claim 8 or 9, characterized in that: The drying is vacuum drying, the vacuum drying temperature is 30 to 60° C., the vacuum degree of the vacuum drying is -0.3 to -0.1 MPa, and the vacuum drying time is 3 to 5 hours.

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