Method for preparing high-purity lithium carbonate and application thereof

Abstract

This application relates to a method for preparing high-purity lithium carbonate and its application. The preparation method includes the following steps: preparing a sodium carbonate solution and a purified lithium sulfate solution; mixing the sodium carbonate solution and the purified lithium sulfate solution and reacting them until the pH of the reaction system reaches 6.6–7.4; separating the solid and liquid components of the reaction system and collecting the solid product; wherein the reaction system is cyclically kept at a temperature between a first temperature T1 and a second temperature T2, where T1 is 15°C–20°C and T2 is 25°C–35°C. By controlling the cyclical holding of the reaction system within a specific temperature range, lithium carbonate can be fully precipitated, and impurities can be avoided. The lithium carbonate obtained by this preparation method has high purity and can be used as battery-grade lithium carbonate; furthermore, the preparation method has a high yield and a short processing time, which is beneficial for its widespread application.

Description

Technical Field

[0001] This application relates to the field of lithium resource extraction technology, specifically to a method for preparing high-purity lithium carbonate and its application. Background Technology

[0002] Lithium carbonate is used in the manufacture of lithium compounds, enamel, and glass. It is a raw material for producing lithium compounds and metallic lithium, and can be used as an additive in the electrolytic bath of aluminum smelting. It has wide applications in the glass, ceramics, pharmaceutical, and food industries, and is also used in synthetic rubber, dyes, semiconductors, military and defense industries, televisions, atomic energy, pharmaceuticals, and catalysts. Battery-grade lithium carbonate is mainly used to prepare lithium-ion battery cathode materials such as lithium cobalt oxide, lithium manganese oxide, ternary materials, and lithium iron phosphate. With the increasing demand for new energy vehicles and mobile electronic products, the demand for lithium carbonate is also growing. However, the traditional lithium carbonate production process involves simply mixing and depositing sodium carbonate solution and lithium sulfate solution, which suffers from drawbacks such as low yield, low purity, and high impurity content. Therefore, developing a new, efficient, and high-purity lithium carbonate production process is particularly important. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for preparing high-purity lithium carbonate that can improve the purity of lithium carbonate and has a high yield and short processing time.

[0004] One aspect of this application provides a method for preparing high-purity lithium carbonate, comprising the following steps:

[0005] Prepare sodium carbonate solution and lithium sulfate purification solution;

[0006] The sodium carbonate solution and the lithium sulfate purification solution are mixed and reacted until the pH of the reaction system is 6.6-7.4;

[0007] The reaction system was subjected to solid-liquid separation, and the solid product was collected.

[0008] The step of mixing and reacting the sodium carbonate solution and the lithium sulfate purification solution includes:

[0009] Step 1: Mix the sodium carbonate solution and the lithium sulfate purification solution and heat to 70℃~80℃ to prepare the reaction system;

[0010] Step 2: The reaction system is cooled to a first temperature T1 and held at that temperature for a period of time; T1 is 15℃~20℃;

[0011] Step 3: Raise the temperature of the reaction system from the first temperature T1 to the second temperature T2 and hold it at that temperature for a period of time; T2 is 25℃~35℃;

[0012] Step 4: Repeat Step 2 and Step 3 in sequence until the pH value of the reaction system reaches 6.6 to 7.4.

[0013] In some embodiments, steps two through four further include continuously introducing carbon dioxide into the reaction system.

[0014] In some embodiments, the heat preservation time in step two is 20 min to 40 min.

[0015] In some embodiments, the heat preservation time in step three is 20 min to 40 min.

[0016] In some embodiments, the sodium carbonate solution is a saturated aqueous solution of sodium carbonate at 60°C to 80°C; the sodium carbonate solution is prepared by the following steps:

[0017] A mixture is prepared by mixing solid sodium carbonate and water;

[0018] The mixture is heated to 60°C–80°C using steam to fully dissolve the sodium carbonate.

[0019] After the sodium carbonate has fully dissolved, the mixture is separated into solid and liquid components to obtain the sodium carbonate solution.

[0020] In some embodiments, the lithium sulfate purified solution is prepared by the following steps:

[0021] Heat the crude lithium sulfate solution to 70℃~80℃;

[0022] The crude lithium sulfate solution at 70℃~80℃ and sodium hydroxide solution are mixed and reacted to precipitate impurities.

[0023] After the reaction of the crude lithium sulfate solution and sodium hydroxide solution is completed, a clear solution is obtained by separation.

[0024] The clarified solution is mixed with activated carbon to adsorb organic impurities and pigments;

[0025] The mixture of the clarified solution and activated carbon is separated into solid and liquid phases to obtain a purified lithium sulfate solution.

[0026] In some embodiments, the method for preparing high-purity lithium carbonate further includes:

[0027] The solid product was purified by electrolysis.

[0028] In some embodiments, the purification step includes:

[0029] The solid product is dissolved to prepare a crude product solution;

[0030] The crude product solution was mixed with sulfuric acid to prepare an electrolyte.

[0031] An electric current is passed through the electrolyte to cause impurities in the electrolyte to precipitate.

[0032] After electrolysis, the electrolyte is separated to obtain a purified solution;

[0033] The purified solution was evaporated and crystallized to obtain the high-purity lithium carbonate.

[0034] In some embodiments, the average particle size D50 of the high-purity lithium carbonate is less than 15 μm.

[0035] Secondly, this application also provides the application of the above-mentioned method for preparing high-purity lithium carbonate in the preparation of lithium-ion batteries.

[0036] The method for preparing high-purity lithium carbonate provided in this application involves controlling the reaction system of sodium carbonate solution and lithium sulfate purification solution to be cyclically kept at temperatures T1 and T2 until the pH value of the reaction system reaches 6.6-7.4. This allows for sufficient precipitation of lithium carbonate and avoids the introduction of impurities. The lithium carbonate prepared by the above-described method has high purity and can be used as battery-grade lithium carbonate. Furthermore, the method has a high yield and short processing time, which is beneficial for its widespread application. Detailed Implementation

[0037] To facilitate understanding of this application, a more complete description will be provided below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0038] In this application, the selection range of "and / or", "or / and", and "and / or" includes any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that the technical solution undoubtedly includes technical solutions connected by "logical AND", and also undoubtedly includes technical solutions connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0039] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more or more.

[0040] In this application, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0041] In this application, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0042] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are used only to describe implementation methods or embodiments with better effects, and should be understood not to constitute a limitation on the scope of protection of this application.

[0043] In this application, terms such as "further," "even further," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0044] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they can be selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0045] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0046] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0047] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0048] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0049] In this application, percentage content refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures, unless otherwise specified.

[0050] In this application, unless otherwise specified, percentage concentrations refer to final concentrations. The final concentration refers to the percentage of the added component in the system after its addition.

[0051] In this application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] One embodiment of this application provides a method for preparing high-purity lithium carbonate, including the following steps S100 to S400.

[0054] Step S100: Prepare sodium carbonate solution and lithium sulfate purification solution.

[0055] In some embodiments, the sodium carbonate solution is a saturated aqueous solution of sodium carbonate at 60°C to 80°C.

[0056] In some embodiments, step S100 includes steps S110 and S120.

[0057] Step S110: Prepare sodium carbonate solution.

[0058] Step S120: Prepare lithium sulfate purification solution.

[0059] It should be noted that the order of steps S110 and S120 in this application is not limited. For example, a sodium carbonate solution can be prepared first, followed by a lithium sulfate purification solution; or, a lithium sulfate purification solution can be prepared first, followed by a sodium carbonate solution; or, a sodium carbonate solution and a lithium sulfate purification solution can be prepared simultaneously.

[0060] In some embodiments, step S110 includes:

[0061] Step S111: Mix sodium carbonate solid and water to prepare a mixture.

[0062] Step S112: Heat the mixture with steam to 60℃~80℃ to fully dissolve the sodium carbonate. Heating the mixture with steam promotes the dissolution of sodium carbonate, shortens the preparation time of the sodium carbonate solution, and controlling the temperature at 60℃~80℃ increases the concentration of sodium carbonate in the solution.

[0063] Step S113: After the sodium carbonate has fully dissolved, separate the solid and liquid mixture to obtain a sodium carbonate solution.

[0064] In some embodiments, step S120 includes:

[0065] Step S121: Heat the crude lithium sulfate solution to 70℃~80℃.

[0066] Step S122: Mix crude lithium sulfate solution at 70℃~80℃ and sodium hydroxide solution to react and precipitate impurities.

[0067] Step S123: After the reaction of the crude lithium sulfate solution and the sodium hydroxide solution is completed, a clear solution is obtained by separation. Mixing the crude lithium sulfate solution and the sodium hydroxide solution at the above temperature can deposit and separate metal impurities, improve the purity of lithium sulfate in the clear solution, and is beneficial to improving the purity of subsequent lithium carbonate preparation.

[0068] Step S124: Mix the clarified solution with activated carbon to adsorb organic impurities and pigments.

[0069] Step S125: Solid-liquid separation of the clarified solution and activated carbon mixture to obtain lithium sulfate purified solution.

[0070] The lithium sulfate purified solution obtained through the above steps S121 to S125 has high purity, which is beneficial to reduce impurities in the subsequent production of lithium carbonate and improve product purity.

[0071] Step S200: Mix sodium carbonate solution and lithium sulfate purification solution and react until the pH of the reaction system is 6.6-7.4.

[0072] Step S200 includes:

[0073] Step S210: Mix the sodium carbonate solution and the purified lithium sulfate solution and heat to 70℃~80℃ to prepare the reaction system. Optionally, the temperature of the reaction system is within the range of 70℃, 72℃, 74℃, 75℃, 76℃, 78℃, 80℃ or any combination thereof.

[0074] Step S220: The reaction system is cooled to a first temperature T1 and held at this temperature for a period of time; T1 is 15℃~20℃. Optionally, T1 is within the range of 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, or any combination thereof. Cooling to 15℃~20℃ and holding at this temperature allows for the precipitation of a large amount of lithium carbonate.

[0075] In some embodiments, the heat preservation time in step S220 is 20 min to 40 min. Optionally, the heat preservation time in step S220 is within the range of 20 min, 25 min, 30 min, 35 min, 40 min, or any combination of the above values.

[0076] Step S230: The reaction system is heated from a first temperature T1 to a second temperature T2 and held at this temperature for a period of time; wherein T2 is 25℃~35℃. Optionally, T2 is within the range of 25℃, 26℃, 280℃, 30℃, 32℃, 34℃, 35℃, or any combination thereof. By heating to 25℃~35℃, some lithium carbonate redissolves, thus controlling the growth rate of the lithium carbonate precipitate.

[0077] In some embodiments, the heat preservation time in step S230 is 20 min to 40 min. Optionally, the heat preservation time in step S230 is within the range of 20 min, 25 min, 30 min, 35 min, 40 min, or any combination of the above values.

[0078] Step S240: Repeat steps S220 and S230 in sequence until the pH value of the reaction system reaches 6.6 to 7.4.

[0079] The above step S200 controls the reaction system to be kept at a constant temperature between T1 and T2 until the pH value of the reaction system reaches 6.6 to 7.4, which enables lithium carbonate to precipitate fully and grow at a suitable rate, while avoiding the introduction of impurities.

[0080] In some embodiments, steps S220 to S240 further include continuously introducing carbon dioxide into the reaction system. By continuously introducing carbon dioxide into the reaction system, the concentration of carbonate ions in the reaction system can be maintained, allowing lithium ions to be fully deposited.

[0081] Step S300: Separate the solid and liquid components of the reaction system and collect the solid product.

[0082] In some embodiments, the solid product can be separated and collected by centrifugation or precipitation in step S300.

[0083] In some embodiments, the preparation method further includes step S400: purifying the solid product by electrolysis. Purifying the solid product by electrolysis can further improve the product purity, which can reach over 99.5%.

[0084] In some embodiments, step S400 includes steps S410 to S450.

[0085] Step S410: Dissolve the solid product to prepare a crude product solution.

[0086] Step S420: Mix the crude solution with sulfuric acid to prepare the electrolyte.

[0087] Step S430: Pass an electric current through the electrolyte to precipitate impurities in the electrolyte.

[0088] Step S440: After electrolysis, the electrolyte is separated to obtain a purified solution.

[0089] Step S450: Evaporate the purified solution to crystallize and obtain high-purity lithium carbonate.

[0090] In some embodiments, the average particle size D50 of high-purity lithium carbonate is less than 15 μm. Specifically, the average particle size D50 of high-purity lithium carbonate is 10 μm to 13 μm.

[0091] The lithium carbonate prepared by the above-mentioned method has high purity and can be used as battery-grade lithium carbonate; moreover, the above-mentioned preparation method has high yield and short processing time, which is conducive to its widespread application.

[0092] Secondly, this application also provides the application of the above-mentioned method for preparing high-purity lithium carbonate in the preparation of lithium-ion batteries.

[0093] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0094] Example 1

[0095] The lithium carbonate preparation method in this embodiment includes the following steps:

[0096] (1) Add sodium carbonate solid to the alkali mixing tank, then add water and mix with sodium carbonate. Heat the mixture with steam to keep the temperature between 60℃ and 80℃. After the sodium carbonate solid is fully dissolved, filter the mixture using a filter press pump to obtain a sodium carbonate solution at 60℃ to 80℃.

[0097] (2) Take the crude lithium sulfate solution, heat it to 80°C, and then filter it initially. Add sodium hydroxide solution to the initially filtered solution and stir to mix. After precipitation is complete, separate the solid and liquid to obtain a clear solution. Then add activated carbon to the clear solution to adsorb organic impurities and pigments, and then filter to remove the activated carbon to obtain purified lithium sulfate solution.

[0098] (3) Mix the sodium carbonate solution obtained in step (1) and the lithium carbonate purification solution obtained in step (2) and heat it to 70℃~80℃. Continuously introduce carbon dioxide into the reactants. Cool the reaction system to 15℃ and keep it for 30 min. Then heat it to 30℃ and keep it for 30 min. Repeat the above heating and cooling process and monitor the pH value of the reactants. Stop the reaction when the pH value is 6.6~7.4. Then cool it to room temperature to allow lithium carbonate to fully precipitate.

[0099] (4) The reaction system of step (3) was centrifuged to obtain a solid product. The solid product was dissolved in water to prepare a crude solution, which was then mixed with sulfuric acid to prepare an electrolyte. An electric current was passed through the electrolyte to cause impurities to deposit. After electrolysis, the electrolyte was separated to obtain a purified solution, which was then evaporated and crystallized to obtain lithium carbonate. The lithium carbonate was dried at 50°C to 60°C to obtain the lithium carbonate prepared in this embodiment.

[0100] The preparation method of this embodiment achieved a yield of 95%, a purity of 99.5% for lithium carbonate, and a total production time of 48 hours. In the preparation method, the utilization rate of sodium carbonate was 98%.

[0101] Comparative Example 1

[0102] The method for preparing lithium carbonate in this comparative example includes the following steps:

[0103] (1) Mix sodium carbonate solid and water at room temperature to dissolve sodium carbonate and prepare sodium carbonate solution.

[0104] (2) The crude lithium sulfate solution is initially filtered, then mixed with sodium carbonate solution, heated to 70℃~80℃ and carbon dioxide is introduced, and then cooled to 15℃ to precipitate lithium carbonate. After sufficient precipitation, the precipitate is collected by centrifugation.

[0105] (3) The reaction system of step (2) was centrifuged to obtain a solid product. The solid product was dissolved in water to prepare a crude solution, which was then mixed with sulfuric acid to prepare an electrolyte. An electric current was passed through the electrolyte to cause impurities to precipitate. After electrolysis, the electrolyte was separated to obtain a purified solution, which was then evaporated and crystallized to obtain lithium carbonate. The lithium carbonate was dried at 50℃~60℃ to obtain the lithium carbonate prepared in this comparative example.

[0106] In this comparative preparation method, the yield of lithium carbonate is 70%, the purity of lithium carbonate is 97%, the total production time is 72 hours, and the utilization rate of sodium carbonate in the preparation method is 85%.

[0107] As can be seen from the comparison between Example 1 and Comparative Example 1, the preparation method of the present application has a higher yield and raw material utilization rate, a shorter process time, and higher purity of the lithium carbonate obtained.

[0108] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The embodiments described above merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing high-purity lithium carbonate, characterized in that, Includes the following steps: Prepare sodium carbonate solution and lithium sulfate purification solution; The sodium carbonate solution and the lithium sulfate purified solution are mixed and reacted until the pH of the reaction system is 6.6~7.4; The reaction system was subjected to solid-liquid separation, and the solid product was collected. The step of mixing and reacting sodium carbonate solution and lithium sulfate purification solution includes: Step 1: Mix the sodium carbonate solution and the lithium sulfate purification solution and heat to 70℃~80℃ to prepare the reaction system; Step 2: The reaction system is cooled to a first temperature T1 and held at that temperature for a period of time; T1 is 15℃~20℃. Step 3: Raise the temperature of the reaction system from the first temperature T1 to the second temperature T2 and hold it at that temperature for a period of time; T2 is 25℃~35℃; Step 4: Repeat Step 2 and Step 3 sequentially until the pH value of the reaction system reaches 6.6~7.4; In steps two through four, carbon dioxide is continuously introduced into the reaction system. The heat preservation time in step two is 20 min to 40 min; The heat preservation time in step three is 20 min to 40 min.

2. The method for preparing high-purity lithium carbonate according to claim 1, characterized in that, The sodium carbonate solution is a saturated aqueous solution of sodium carbonate at a temperature of 60℃~80℃; the sodium carbonate solution is prepared by the following steps: A mixture is prepared by mixing solid sodium carbonate and water; The mixture is heated to 60°C to 80°C using steam to fully dissolve the sodium carbonate. After the sodium carbonate has fully dissolved, the mixture is separated into solid and liquid components to obtain the sodium carbonate solution.

3. The method for preparing high-purity lithium carbonate according to claim 1, characterized in that, The purified lithium sulfate solution is prepared by the following steps: Heat the crude lithium sulfate solution to 70℃~80℃; The crude lithium sulfate solution and sodium hydroxide solution at 70℃~80℃ are mixed and reacted to precipitate impurities. After the reaction of the crude lithium sulfate solution and sodium hydroxide solution is completed, a clear solution is obtained by separation. The clarified solution is mixed with activated carbon to adsorb organic impurities and pigments; The mixture of the clarified solution and activated carbon is separated into solid and liquid phases to obtain a purified lithium sulfate solution.

4. The method for preparing high-purity lithium carbonate according to claim 1, characterized in that, Also includes: The solid product was purified by electrolysis.

5. The method for preparing high-purity lithium carbonate according to claim 4, characterized in that, The purification steps include: The solid product is dissolved to prepare a crude product solution; The crude product solution was mixed with sulfuric acid to prepare an electrolyte. An electric current is passed through the electrolyte to cause impurities in the electrolyte to precipitate. After electrolysis, the electrolyte is separated to obtain a purified solution; The purified solution was evaporated and crystallized to obtain the high-purity lithium carbonate.

6. The method for preparing high-purity lithium carbonate according to any one of claims 1 to 5, characterized in that, The average particle size D50 of the high-purity lithium carbonate is less than 15 μm.

7. The application of the method for preparing high-purity lithium carbonate according to any one of claims 1 to 6 in the preparation of lithium-ion batteries.