Synthesis process of lithium trichloroaluminate for electrolyte of lithium sulfoxyl chloride battery

Abstract

The application provides a synthesis process of lithium trichloroaluminate for lithium sulfonyl chloride battery electrolyte, which comprises the following steps: step one, raw material pretreatment: anhydrous lithium chloride and anhydrous aluminum chloride are selected as raw materials, sulfonyl chloride is used as a reaction solvent, and all the raw materials are stored and transported in an inert atmosphere; step two, atmosphere replacement: the reaction kettle is vacuumized to below-0.095 MPa, then high-purity inert gas is introduced for replacement, and the vacuumization and gas filling operation is repeated for 3-5 times; step three, gradient feeding and segmented temperature control complexation reaction; the prepared lithium trichloroaluminate product has a purity of more than 99.5%, and the total water content is controlled to be below 10 ppm, so that the content of free chlorine ions and metal impurities is significantly reduced; the high-purity product has good matching with the sulfonyl chloride solvent, after being prepared into an electrolyte, the ion conductivity of the battery can be improved, the corrosion of the lithium negative electrode sheet can be inhibited, the self-discharge of the battery can be reduced, and the voltage lag phenomenon can be slowed down, so that the storage life of the lithium sulfonyl chloride battery is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of lithium primary battery electrolyte preparation technology, specifically relating to a synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte. Background Technology

[0002] Lithium thionyl chloride (Li / SOCl2) batteries are among the highest energy density commercially available chemical power sources, boasting advantages such as high operating voltage, low leakage current, long storage life, and a wide operating temperature range. They are widely used in industrial instruments, security equipment, passive IoT devices, and military equipment. Lithium trichloroaluminate (LiAlCl4) is the core conductive solute in the electrolyte of lithium thionyl chloride batteries, which is typically composed of lithium trichloroaluminate dissolved in thionyl chloride solvent. The purity, water content, and impurity content of lithium trichloroaluminate directly determine the battery's conductivity, voltage hysteresis, self-discharge, and storage life.

[0003] Currently, the mainstream industrial synthesis methods for lithium trichloroaluminate generally suffer from significant process defects. The direct solid-phase mixing and melting method, due to its high reaction temperature, is prone to localized overheating and decomposition of materials, producing toxic and corrosive gases such as hydrogen chloride and chlorine. This results in numerous byproducts, unreacted raw materials entrained in the product, low purity, and severe equipment corrosion due to the high-temperature system, posing significant production safety risks. Furthermore, it is difficult to thoroughly remove moisture from the product. The conventional liquid-phase reaction method directly adds solid raw materials to thionyl chloride at room temperature, leading to uneven mixing and excessively high local concentrations that can easily trigger violent exothermic reactions, causing thionyl chloride decomposition and introducing organic and chlorine oxide impurities. It also suffers from incomplete reaction, uneven product crystal size, and difficulty in purification. Lithium trichloroaluminate prepared by these existing processes generally exhibits defects such as high water content, excessive metallic impurities, and excessive free chloride ions. When used in lithium thionyl chloride batteries, these defects exacerbate the corrosion of the negative lithium electrode, increase battery self-discharge, cause significant voltage hysteresis, and drastically shorten battery life, failing to meet the requirements of high-end, long-life lithium thionyl chloride batteries. Summary of the Invention

[0004] This invention provides a synthesis process for lithium trichloroaluminate in lithium thionyl chloride battery electrolyte, which solves the technical problems mentioned in the background art, such as excessively vigorous reaction, numerous by-products, low product purity, difficulty in controlling moisture and impurities, poor safety in large-scale production, and the resulting lithium trichloroaluminate causing high self-discharge, voltage hysteresis, and poor cycle and storage performance in batteries.

[0005] The technical solution adopted in this invention is: a synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte, comprising the following steps:

[0006] Step 1: Raw material pretreatment: Anhydrous lithium chloride and anhydrous aluminum trichloride are selected as raw materials, and thionyl chloride is used as the reaction solvent. All raw materials are stored and transported under an inert atmosphere. By selecting anhydrous lithium chloride, anhydrous aluminum trichloride, and thionyl chloride with low water content, and storing and transporting them under an inert atmosphere, the purpose is to prevent the introduction of external moisture and oxygen from the source, avoid hydrolysis of raw materials or side reactions, and provide a basic material guarantee for the subsequent synthesis of high-purity, low-moisture lithium trichloroaluminate.

[0007] Step 2, Atmosphere Replacement: Evacuate the reactor to below -0.095MPa, then introduce high-purity inert gas for replacement. Repeat the evacuation and gas filling operation 3-5 times. The function of performing deep evacuation and repeated replacement with high-purity inert gas is to thoroughly remove the residual air in the reactor, which can form a low-oxygen, ultra-dry, and sealed reaction environment to prevent the subsequent reactants from deteriorating due to contact with trace amounts of moisture and oxygen during high temperature or complexation process.

[0008] Step 3: Gradient feeding and segmented temperature-controlled complexation reaction:

[0009] a. Add thionyl chloride to the reactor, start stirring, and control the stirring speed at 60-120 r / min; pre-adding thionyl chloride and starting stirring at a specific speed provides a good fluid dispersion medium for the solid raw materials and ensures uniform mass transfer of materials;

[0010] b. Prepare raw materials according to a molar ratio of lithium chloride to aluminum trichloride = 1:1; first, slowly add anhydrous lithium chloride to the thionyl chloride solvent in 3-5 batches, controlling the system temperature at 20-35℃, with an interval of 15-30 minutes between each batch; the use of a strict 1:1 molar ratio and the slow addition of lithium chloride in batches at a lower temperature is to ensure that lithium chloride is fully dispersed and slightly dissolved in the thionyl chloride, preventing local solid aggregation and controlling the heat of solution;

[0011] c. After lithium chloride is added, heat the system to 40-55℃, then add anhydrous aluminum trichloride to the reaction system in 4-6 batches at a uniform rate, with an interval of 20-40 minutes between each batch, and control the maximum temperature of the system to not exceed 60℃; after heating, aluminum trichloride can be added in batches at a uniform rate and the maximum temperature can be limited. The purpose is to control the rate of the strongly exothermic liquid-phase complexation reaction and avoid decomposition of thionyl chloride solvent due to excessively high local concentration or local overheating, thereby inhibiting the generation of by-products from the source;

[0012] d. After aluminum trichloride is added, the mixture is kept at 40-55℃ and stirred for 4-8 hours to obtain crude lithium trichloroaluminate solution. The purpose of keeping it warm and stirring is to provide sufficient reaction time to ensure that lithium chloride and aluminum trichloride fully complete chemical complexation.

[0013] Step 4, Low-temperature ripening treatment: Cool the reaction system to 10-20℃ and stir for 2-4 hours; by lowering the system temperature and extending the stirring time, the trace amounts of unreacted raw materials remaining in the system due to feeding deviation or mass transfer limitation can be deeply complexed, promoting the reaction to be more complete, reducing the residue of free ions, and improving the overall conversion rate of raw materials.

[0014] Step 5: Low-temperature vacuum purification: Maintain the system temperature at 10-25℃, and perform vacuum distillation on the reactor. Control the vacuum degree to -0.08--0.09MPa and distill for 2-3 hours to obtain purified lithium trichloroaluminate mother liquor. Vacuum distillation under limited low temperature and vacuum conditions can selectively remove trace amounts of low-boiling-point impurities, residual free chlorides, and products of slight decomposition of thionyl chloride generated in the system, thereby achieving preliminary purification of the crude liquor and improving the purity of the mother liquor.

[0015] Step Six: Sealed Crystallization and Vacuum Drying: Transfer the refined mother liquor to a sealed crystallization vessel and slowly cool it to 0-5℃ under inert gas protection. Maintain this temperature for 6-12 hours to allow crystals to precipitate. Place the crystals after solid-liquid separation under vacuum conditions of ≥-0.09MPa and 40-50℃ for 8-12 hours to obtain anhydrous lithium trichloroaluminate. The slow cooling and constant-temperature crystallization, solid-liquid separation, and final heating and vacuum drying utilize the difference in solubility to allow high-purity lithium trichloroaluminate crystals to precipitate in a regular pattern, achieving separation from the free impurity mother liquor. Subsequent vacuum drying can deeply remove trace amounts of volatile impurities and moisture remaining on the crystal surface and inside without damaging the crystal structure, ultimately obtaining a finished product that meets the requirements for high electrochemical performance.

[0016] In step one, the anhydrous lithium chloride is electronic grade with a moisture content ≤5ppm; the anhydrous aluminum trichloride is sublimation grade with a moisture content ≤5ppm; and the thionyl chloride is ultra-dry thionyl chloride with a moisture content ≤3ppm. By limiting anhydrous lithium chloride to electronic grade, anhydrous aluminum trichloride to sublimation grade, and thionyl chloride to ultra-dry grade, and strictly controlling their respective upper limits of moisture content, the technical advantage lies in establishing a stringent low-moisture standard from the raw material end. This prevents the finished product from exceeding the moisture content limit due to moisture inherent in the raw materials themselves, thus ensuring the ultra-dry characteristics of the final product.

[0017] After the atmosphere replacement in step two is completed, the oxygen content in the reactor is <10ppm and the water content is <5ppm. Controlling the oxygen and water content within an extremely low quantitative range after atmosphere replacement has the advantage of achieving precise quantitative control of the internal environmental indicators of the reactor, avoiding side reactions such as hydrolysis and oxidation of the reactants due to residual moisture or oxygen in the environment, and improving the stability of batch production.

[0018] In step three, the mass ratio of thionyl chloride solvent to lithium chloride is 8:1 to 15:1. Limiting the mass ratio of thionyl chloride solvent to lithium chloride to 8:1 to 15:1 aims to provide an optimal ratio of dilution and heat transfer media. If the ratio is too low, the material becomes too viscous, resulting in uneven stirring and difficulty in heat dissipation; if the ratio is too high, it increases the energy consumption of subsequent distillation and crystallization. This range balances reaction heat control and production energy consumption while ensuring sufficient dispersion and dissolution of the material.

[0019] In step three, during the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is controlled at 80 r / min. The main purpose of this setting is that this speed can provide a flow field with moderate shear force, which can ensure that the solid material is rapidly and uniformly dispersed in the thionyl chloride solvent and promote the complexation reaction, while avoiding mechanical friction heat generation or material splashing caused by excessive speed.

[0020] In step four, during the low-temperature maturation stage, the stirring speed is controlled at 40-60 r / min. This setting is because the material has been basically transformed during the maturation stage. This lower speed can maintain the uniformity of the fluid in the system, promote the contact and collision of trace amounts of unreacted material, reduce energy consumption, and avoid excessive stirring from having an adverse shear effect on the material that is about to enter the crystallization stage.

[0021] All processes from step one to step six are carried out in a closed inert atmosphere system, and contact with air is strictly prohibited throughout the process. The purpose is to achieve a physical environmental barrier throughout the entire process, completely eliminating the risk of moisture and oxygen absorption due to contact with outside air during the transfer and operation of each process, and ensuring a water-free and oxygen-free environment for the entire process chain.

[0022] The inert gas or inert atmosphere is high-purity argon or high-purity nitrogen with a purity of ≥99.999%. The advantage of this setting is that the protective gas itself is almost free of moisture and oxygen impurities, and will not introduce secondary pollution to the highly sensitive reaction system, thus ensuring the chemical inertness and purity of the environment.

[0023] The prepared anhydrous lithium trichloroaluminate product has a purity of ≥99.5% and a total water content of ≤10ppm.

[0024] The beneficial effects of this invention are as follows:

[0025] The lithium trichloroaluminate product prepared by this invention has a purity of over 99.5% and a total water content controlled below 10 ppm, significantly reducing the content of free chloride ions and metal impurities. This high-purity product has good compatibility with thionyl chloride solvent. When formulated into an electrolyte, it can improve the ionic conductivity of the battery, inhibit the corrosion of the lithium anode sheet, reduce battery self-discharge, and slow down voltage hysteresis, thereby extending the storage life of lithium thionyl chloride batteries.

[0026] This invention employs a liquid-phase complexation process, adding anhydrous lithium chloride and anhydrous aluminum trichloride in batches and at intervals to ensure uniform dispersion and dissolution of the raw materials in the reaction medium. This prevents violent exothermic reactions caused by excessively high local material concentrations. Since the maximum reaction temperature throughout the process does not exceed 60°C, the side reaction decomposition of thionyl chloride and the generation of chlorine oxide impurities are suppressed. There is no release of large amounts of toxic and corrosive tail gas, reducing equipment corrosion and ensuring production safety.

[0027] This invention involves low-temperature curing after the complexation reaction, which promotes the full complexation of trace amounts of unreacted raw materials in the system, improves the raw material conversion rate and reduces the residue of free ions. The entire process is combined with multiple rounds of vacuuming and inert gas replacement, and the entire process is in a closed state, which achieves stable control of moisture and oxygen indicators, high production repeatability, and is suitable for continuous industrial production. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment describes a synthesis process for lithium trichloroaluminate in a lithium thionyl chloride battery electrolyte. All steps are carried out within a closed, inert atmosphere system, with strict prohibition of contact with air throughout. The inert gas used is high-purity argon with a purity of 99.999%. The specific process steps are as follows:

[0031] Step 1: Raw material pretreatment

[0032] Electronic-grade anhydrous lithium chloride (5 ppm moisture content) and sublimed anhydrous aluminum trichloride (5 ppm moisture content) were selected as raw materials, and ultra-dry thionyl chloride (3 ppm moisture content) was used as the reaction solvent. All raw materials were stored and transported under the aforementioned high-purity argon inert atmosphere.

[0033] Step 2: Atmosphere Replacement

[0034] The corrosion-resistant reactor was evacuated to -0.095 MPa, then purged with high-purity argon gas. This evacuation and purging process was repeated three times. After the atmosphere replacement was completed, the oxygen content inside the reactor was measured to be 9 ppm and the water content to be 4 ppm.

[0035] Step 3: Gradient feeding and segmented temperature-controlled complexation reaction

[0036] a. Add the ultra-dry thionyl chloride to the reactor, start stirring, and control the stirring speed at 60 r / min; wherein, the mass ratio of the thionyl chloride solvent to lithium chloride is controlled at 8:1;

[0037] b. Prepare the raw materials according to a molar ratio of lithium chloride to aluminum trichloride of 1:1. First, slowly add anhydrous lithium chloride to the thionyl chloride solvent in 3 batches, controlling the system temperature at 20°C during the addition process, with an interval of 30 minutes between each batch to ensure that the lithium chloride is fully dissolved;

[0038] c. After lithium chloride is added, the system temperature is raised to 55°C. During the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is increased and controlled at 80 r / min. Then, anhydrous aluminum trichloride is added to the reaction system in 4 batches at a uniform rate, with an interval of 40 min between each batch, and the maximum temperature of the system is controlled not to exceed 60°C.

[0039] d. After aluminum trichloride is added, the mixture is kept at 55°C and stirred for 4 hours to obtain crude lithium trichloroaluminate solution.

[0040] Step 4: Low-temperature curing treatment

[0041] Cool the reaction system to 10°C, reduce the stirring speed to 40 r / min, and continue stirring and maturing for 4 hours.

[0042] Step 5: Low-temperature vacuum purification

[0043] The system temperature was kept at 25℃, and the reactor was subjected to vacuum distillation with the vacuum degree controlled at -0.08MPa for 3 hours to remove trace amounts of low-boiling-point impurities from the system, thus obtaining refined lithium trichloroaluminate mother liquor.

[0044] Step Six: Sealed Crystallization and Vacuum Drying

[0045] The refined lithium trichloroaluminate mother liquor was transferred to a closed crystallization vessel and slowly cooled to 0°C under the protection of high-purity argon. The mixture was then kept at this temperature for 12 hours to allow crystals to precipitate. After solid-liquid separation under an inert atmosphere, the collected crystals were placed in a vacuum drying oven and vacuum-dried for 8 hours at a vacuum of -0.09 MPa and 50°C to obtain the final product: anhydrous lithium trichloroaluminate.

[0046] According to the test results, the anhydrous lithium trichloroaluminate product prepared in this embodiment has a purity of 99.51% and a total water content of 9.2 ppm.

[0047] Example 2

[0048] This embodiment describes a synthesis process for lithium trichloroaluminate in a lithium thionyl chloride battery electrolyte. All steps are carried out within a closed, inert atmosphere system, with strict prohibition of contact with air throughout. The inert gas used is high-purity nitrogen with a purity of 99.999%. The specific process steps are as follows:

[0049] Step 1: Raw material pretreatment

[0050] Electronic-grade anhydrous lithium chloride (3 ppm moisture content) and sublimed anhydrous aluminum trichloride (4 ppm moisture content) were selected as raw materials, and ultra-dry thionyl chloride (2 ppm moisture content) was used as the reaction solvent. All raw materials were stored and transported under the aforementioned high-purity nitrogen inert atmosphere.

[0051] Step 2: Atmosphere Replacement

[0052] The corrosion-resistant reactor was evacuated to -0.098 MPa, then purged with high-purity nitrogen. This evacuation and purging process was repeated five times. After the atmosphere replacement was completed, the oxygen content inside the reactor was measured to be 4 ppm and the water content to be 2 ppm.

[0053] Step 3: Gradient feeding and segmented temperature-controlled complexation reaction

[0054] a. Add the ultra-dry thionyl chloride to the reactor, start stirring, and control the stirring speed at 120 r / min; wherein, the mass ratio of the thionyl chloride solvent to lithium chloride is controlled at 15:1;

[0055] b. Prepare the raw materials according to a molar ratio of lithium chloride to aluminum trichloride of 1:1. First, slowly add anhydrous lithium chloride to the thionyl chloride solvent in 5 batches, controlling the system temperature at 35°C during the addition process, with an interval of 15 minutes between each batch to ensure that the lithium chloride is fully dissolved;

[0056] c. After lithium chloride is added, the system is heated to 40°C. During the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is controlled at 80 r / min. Then, anhydrous aluminum trichloride is added to the reaction system in 6 batches at a uniform rate, with an interval of 20 min between each batch, and the maximum temperature of the system is controlled not to exceed 60°C.

[0057] d. After aluminum trichloride is added, the mixture is kept at 40°C and stirred for 8 hours to obtain crude lithium trichloroaluminate solution.

[0058] Step 4: Low-temperature curing treatment

[0059] Cool the reaction system to 20°C, reduce the stirring speed to 60 r / min, and continue stirring and maturing for 2 hours.

[0060] Step 5: Low-temperature vacuum purification

[0061] The system temperature was kept at 10℃, and the reactor was subjected to vacuum distillation with the vacuum degree controlled at -0.09MPa for 2 hours to remove trace amounts of low-boiling-point impurities from the system, thus obtaining refined lithium trichloroaluminate mother liquor.

[0062] Step Six: Sealed Crystallization and Vacuum Drying

[0063] The refined lithium trichloroaluminate mother liquor was transferred to a sealed crystallization vessel and slowly cooled to 5°C under high-purity nitrogen protection. The mixture was then kept at this temperature for 6 hours to allow crystals to precipitate. After solid-liquid separation under an inert atmosphere, the collected crystals were placed in a vacuum drying oven and vacuum-dried for 12 hours at a vacuum of -0.095 MPa and 40°C to obtain the final product: anhydrous lithium trichloroaluminate.

[0064] The anhydrous lithium trichloroaluminate product prepared in this embodiment has a purity of 99.62% and a total water content of 7.5 ppm, according to the test results.

[0065] Example 3

[0066] This embodiment describes a synthesis process for lithium trichloroaluminate in a lithium thionyl chloride battery electrolyte. All steps are carried out within a closed, inert atmosphere system, with strict prohibition of contact with air throughout. The inert gas used is high-purity argon with a purity of 99.999%. The specific process steps are as follows:

[0067] Step 1: Raw material pretreatment

[0068] Electronic-grade anhydrous lithium chloride (4 ppm moisture content) and sublimed anhydrous aluminum trichloride (3 ppm moisture content) were selected as raw materials, and ultra-dry thionyl chloride (2.5 ppm moisture content) was used as the reaction solvent. All raw materials were stored and transported under the aforementioned high-purity argon inert atmosphere.

[0069] Step 2: Atmosphere Replacement

[0070] The corrosion-resistant reactor was evacuated to -0.096 MPa, then purged with high-purity argon gas. This evacuation and purging process was repeated four times. After the atmosphere replacement was completed, the oxygen content inside the reactor was measured to be 6 ppm and the water content to be 3 ppm.

[0071] Step 3: Gradient feeding and segmented temperature-controlled complexation reaction

[0072] a. Add the ultra-dry thionyl chloride to the reactor, start stirring, and control the stirring speed at 90 r / min; wherein, the mass ratio of the thionyl chloride solvent to lithium chloride is controlled at 11:1;

[0073] b. Prepare the raw materials according to a molar ratio of lithium chloride to aluminum trichloride of 1:1. First, slowly add anhydrous lithium chloride to the thionyl chloride solvent in 4 batches, controlling the system temperature at 26°C during the addition process, with an interval of 20 minutes between each batch to ensure that the lithium chloride is fully dissolved;

[0074] c. After lithium chloride is added, the system is heated to 48°C. During the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is controlled at 80 r / min. Then, anhydrous aluminum trichloride is added to the reaction system in 5 batches at a uniform rate, with an interval of 30 min between each batch, and the maximum temperature of the system is controlled not to exceed 60°C.

[0075] d. After aluminum trichloride is added, the mixture is kept at 48°C and stirred for 6 hours to obtain crude lithium trichloroaluminate solution.

[0076] Step 4: Low-temperature curing treatment

[0077] Cool the reaction system to 14°C, reduce the stirring speed to 50 r / min, and continue stirring and maturing for 3 hours.

[0078] Step 5: Low-temperature vacuum purification

[0079] The system temperature was kept at 18℃, and the reactor was subjected to vacuum distillation with the vacuum degree controlled at -0.085MPa for 2.5h to remove trace amounts of low-boiling-point impurities from the system, thus obtaining refined lithium trichloroaluminate mother liquor.

[0080] Step Six: Sealed Crystallization and Vacuum Drying

[0081] The refined lithium trichloroaluminate mother liquor was transferred to a sealed crystallization vessel and slowly cooled to 3°C under high-purity argon protection. The mixture was then kept at this temperature for 9 hours to allow crystals to precipitate. After solid-liquid separation under an inert atmosphere, the collected crystals were placed in a vacuum drying oven and vacuum-dried for 10 hours at a vacuum of -0.092 MPa and 45°C to obtain the final anhydrous lithium trichloroaluminate product.

[0082] According to the test results, the anhydrous lithium trichloroaluminate product prepared in this embodiment has a purity of 99.71% and a total water content of 5.8 ppm.

[0083] Example 4

[0084] This embodiment describes a synthesis process for lithium trichloroaluminate in a lithium thionyl chloride battery electrolyte. All steps are carried out within a closed, inert atmosphere system, with strict prohibition of contact with air throughout. The inert gas used is high-purity nitrogen with a purity of 99.999%. The specific process steps are as follows:

[0085] Step 1: Raw material pretreatment

[0086] Electronic-grade anhydrous lithium chloride (2 ppm moisture content) and sublimed anhydrous aluminum trichloride (2 ppm moisture content) were selected as raw materials, and ultra-dry thionyl chloride (1.5 ppm moisture content) was used as the reaction solvent. All raw materials were stored and transported under the aforementioned high-purity nitrogen inert atmosphere.

[0087] Step 2: Atmosphere Replacement

[0088] The corrosion-resistant reactor was evacuated to -0.097 MPa, then purged with high-purity nitrogen. This evacuation and purging process was repeated four times. After the atmosphere replacement was completed, the oxygen content inside the reactor was measured to be 3 ppm and the water content to be 1.5 ppm.

[0089] Step 3: Gradient feeding and segmented temperature-controlled complexation reaction

[0090] a. Add the ultra-dry thionyl chloride to the reactor, start stirring, and control the stirring speed at 100 r / min; wherein, the mass ratio of the thionyl chloride solvent to lithium chloride is controlled at 13:1;

[0091] b. Prepare the raw materials according to a molar ratio of lithium chloride to aluminum trichloride of 1:1. First, slowly add anhydrous lithium chloride to the thionyl chloride solvent in 4 batches, controlling the system temperature at 30°C during the addition process, with an interval of 25 minutes between each batch to ensure that the lithium chloride is fully dissolved;

[0092] c. After lithium chloride is added, the system is heated to 52°C. During the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is controlled at 80 r / min. Then, anhydrous aluminum trichloride is added to the reaction system in 5 batches at a uniform rate, with an interval of 25 min between each batch, and the maximum temperature of the system is controlled not to exceed 60°C.

[0093] d. After aluminum trichloride is added, the mixture is kept at 52°C and stirred for 5 hours to obtain crude lithium trichloroaluminate solution.

[0094] Step 4: Low-temperature curing treatment

[0095] The reaction system was cooled to 17°C, and the stirring speed was controlled at 45 r / min. The stirring and maturation were continued for 3.5 h.

[0096] Step 5: Low-temperature vacuum purification

[0097] The system temperature was kept at 22℃, and the reactor was subjected to vacuum distillation with the vacuum degree controlled at -0.088MPa for 2.2h to remove trace amounts of low-boiling-point impurities from the system, thus obtaining refined lithium trichloroaluminate mother liquor.

[0098] Step Six: Sealed Crystallization and Vacuum Drying

[0099] The refined lithium trichloroaluminate mother liquor was transferred to a sealed crystallization vessel and slowly cooled to 2°C under high-purity nitrogen protection. The mixture was then kept at this temperature for 10 hours to allow crystals to precipitate. After solid-liquid separation under an inert atmosphere, the collected crystals were placed in a vacuum drying oven and vacuum-dried for 9 hours at a vacuum of -0.093 MPa and 48°C to obtain the final product: anhydrous lithium trichloroaluminate.

[0100] According to the test results, the anhydrous lithium trichloroaluminate product prepared in this embodiment has a purity of 99.78% and a total water content of 4.6 ppm.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A synthesis process for lithium trichloroaluminate in lithium thionyl chloride battery electrolyte, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Anhydrous lithium chloride and anhydrous aluminum trichloride are selected as raw materials, and thionyl chloride is used as the reaction solvent. All raw materials are stored and transported under an inert atmosphere. Step 2, Atmosphere Replacement: Evacuate the reactor to below -0.095MPa, then introduce high-purity inert gas for replacement. Repeat the evacuation and gas filling operation 3-5 times. Step 3: Gradient feeding and segmented temperature-controlled complexation reaction: a. Add thionyl chloride to the reactor, start stirring, and control the stirring speed at 60-120 r / min; b. Prepare raw materials according to a molar ratio of lithium chloride:aluminum trichloride = 1:1; first, slowly add anhydrous lithium chloride to thionyl chloride solvent in 3-5 batches, control the system temperature at 20-35℃, and the interval between each batch of addition is 15-30 minutes. c. After the lithium chloride is added, heat the system to 40-55℃, and then add anhydrous aluminum trichloride to the reaction system in 4-6 batches at a uniform rate, with an interval of 20-40 minutes between each batch, and control the maximum temperature of the system to not exceed 60℃. d. After aluminum trichloride is added, the mixture is kept at 40-55℃ and stirred for 4-8 hours to obtain crude lithium trichloroaluminate solution; Step 4: Low-temperature ripening treatment: Cool the reaction system to 10-20℃ and stir for 2-4 hours. Step 5: Low-temperature vacuum purification: Maintain the system temperature at 10-25℃, perform vacuum distillation on the reactor, control the vacuum degree to -0.08--0.09MPa, and distill for 2-3 hours to obtain refined lithium trichloroaluminate mother liquor; Step 6, Closed Crystallization and Vacuum Drying: Transfer the refined mother liquor into a closed crystallization vessel, slowly cool it to 0-5℃ under inert gas protection, and let it stand at a constant temperature for 6-12 hours to crystallize and precipitate crystals; place the crystals after solid-liquid separation under vacuum conditions of ≥-0.09MPa and 40-50℃ for 8-12 hours to obtain anhydrous lithium trichloroaluminate product.

2. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: In step one, the anhydrous lithium chloride is electronic grade with a water content ≤5ppm; the anhydrous aluminum trichloride is sublimation grade with a water content ≤5ppm; and the thionyl chloride is ultra-dry thionyl chloride with a water content ≤3ppm.

3. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: After the atmosphere replacement in step two is completed, the oxygen content in the reactor is <10ppm and the water content is <5ppm.

4. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: In step three, the mass ratio of the thionyl chloride solvent to lithium chloride is 8:1-15:

1.

5. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: In step three, during the gradient feeding and segmented temperature-controlled complexation reaction stage, the stirring speed is controlled at 80 r / min.

6. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: In step four, during the low-temperature curing stage, the stirring speed is controlled at 40-60 r / min.

7. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: All processes from step one to step six are carried out in a closed inert atmosphere system, and contact with air is strictly prohibited throughout the entire process.

8. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1 or 7, characterized in that: The inert gas or inert atmosphere is high-purity argon or high-purity nitrogen with a purity of ≥99.999%.

9. The synthesis process of lithium trichloroaluminate for lithium thionyl chloride battery electrolyte according to claim 1, characterized in that: The prepared anhydrous lithium trichloroaluminate product has a purity of ≥99.5% and a total water content of ≤10ppm.