Method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate

Abstract

The invention relates to the field of preparation of battery grade carbonic acid, and provides a method for preparing battery grade lithium carbonate by purifying crude lithium carbonate, the preparation method comprises the following steps: screening crude lithium carbonate from different sources, mixing lithium carbonate according to a certain solid-to-liquid ratio, and stirring to obtain dispersed slurry; cO2 gas is introduced into the obtained dispersed slurry for pre-hydrogenation treatment, and mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate is obtained; adding a certain amount of lithium-containing reagent into the obtained mixed slurry, and heating the mixed slurry in a stirring state to obtain treated slurry; carrying out solid-liquid separation to obtain industrial-grade wet lithium carbonate and a lithium bicarbonate solution, and carrying out thermal decomposition on the lithium bicarbonate solution to obtain industrial-grade wet lithium carbonate; and carrying out size mixing, hydrogenation, thermal decomposition and solid-liquid separation on the two parts of industrial-grade wet lithium carbonate, and drying a filter cake to obtain the battery-grade lithium carbonate. The process flow is simple, the impurity removal efficiency is high, and the battery-grade lithium carbonate can be economically and efficiently prepared from the crude lithium carbonate raw materials with different sources and different qualities.

Description

Technical Field

[0001] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate

[0002] The invention relates to a method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate. The invention aims to prepare battery-grade lithium carbonate by a simple and efficient method in view of the current situation that crude lithium carbonate with a purity of less than 98.5wt% cannot be used to prepare battery-grade lithium carbonate economically and efficiently. Background Art

[0003] Battery-grade lithium carbonate is an important basic lithium salt as the main raw material for preparing lithium iron phosphate and ternary lithium batteries. In recent years, with the rapid development of new energy vehicles, energy storage and other industries, the demand for battery-grade lithium carbonate has increased year by year. Battery-grade lithium carbonate is all purified from industrial-grade lithium carbonate. The main purification methods include hydrogenation decomposition, causticization, recrystallization and other methods, which are relatively mature at present. Industrial-grade lithium carbonate refers to products with a purity of >98.5wt% and clear requirements for impurities such as sulfate, chlorine, sodium and calcium. The production process of industrial-grade lithium carbonate is almost entirely prepared by the reaction and crystallization of lithium sulfate and sodium carbonate. Due to the complex and difficult control of the reaction and crystallization process, the immature production process and the limitation of raw materials, a large number of primary products cannot meet the standards of industrial-grade lithium carbonate. The impurities such as sulfate and sodium in the product are seriously exceeded, and only crude lithium carbonate (85-98.5wt%) can be obtained. Secondly, since the salt lake contains a large amount of impurities such as K and Cl, the excessive K and Cl in crude lithium carbonate is also very serious. It is estimated that crude lithium carbonate accounts for more than 50% of primary lithium carbonate products, and it is impossible to directly produce battery-grade lithium carbonate through existing purification methods, which makes it difficult to meet the demand for raw materials in the rapidly growing new energy industry. Therefore, it is of great significance to use crude lithium carbonate as a raw material to economically and efficiently produce battery-grade lithium carbonate.

[0004] At present, a lot of research has been done in China on the preparation of battery-grade lithium carbonate from crude lithium carbonate. The following patents report on the preparation of battery-grade lithium carbonate from crude lithium carbonate:

[0005] 1. Patent CN202111585207.6 discloses a method for purifying battery-grade lithium carbonate from crude lithium carbonate. This method adds crude lithium carbonate to dilute sulfuric acid to completely dissolve it, adds sodium carbonate after filtration, and then obtains battery-grade lithium carbonate through high-temperature aging, washing and other steps. This method consumes a large amount of sulfuric acid and sodium carbonate, which is equivalent to recrystallizing the crude lithium carbonate after full dissolution. Secondly, hydrogen peroxide needs to be added in this process. The actual consumption is large and the operating cost is high.

[0006] 2. Patent CN201910695377.6 discloses a method for purifying and preparing battery-grade lithium carbonate from crude lithium carbonate. The method first prepares crude lithium carbonate into a slurry, and then reacts it with saturated sodium carbonate to obtain industrial-grade lithium carbonate; then the industrial-grade lithium carbonate is prepared into battery-grade lithium carbonate by hydrogenation decomposition. This avoids the consumption of dilute sulfuric acid, but it also requires the consumption of a large amount of sodium carbonate and hydrogen peroxide. Secondly, in the process of purifying industrial-grade lithium carbonate, this method mainly targets Ca 2+ Mg 2+ and borate removal, but no reports have been found on the removal of sulfate, chloride, sodium and potassium.

[0007] 3. Patent CN202310746181.1 discloses a method for preparing battery-grade lithium carbonate by foam flotation purification of crude lithium carbonate. This method prepares crude lithium carbonate into lithium bicarbonate solution by hydrogenation operation, and then uses foam flotation to remove insoluble impurities. The disadvantage of this method is that the crude lithium carbonate needs to be completely hydrogenated before operation, the liquid-to-solid ratio is too high, the liquid processing volume is too large, and the operating cost is too high; secondly, the removal effect of soluble impurities such as sulfate, chlorine, sodium, and potassium is not good, and there is no specific description of the change in impurity content in the embodiment.

[0008] In summary, the existing methods for purifying crude lithium carbonate to prepare battery-grade lithium carbonate either require that the lithium carbonate be completely dissolved into lithium sulfate or lithium bicarbonate before preliminary purification, which has problems such as large liquid processing volume, low production capacity, and poor ability to handle soluble impurities; or it is necessary to add a large amount of sodium carbonate, hydrogen peroxide and other reagents to the system, which has problems such as complex waste liquid treatment and large reagent consumption. The above difficulties have caused the existing methods for purifying crude lithium carbonate to prepare battery-grade lithium carbonate to have complex operations and high costs. Therefore, how to simply and efficiently purify crude lithium carbonate to prepare battery-grade lithium carbonate is very critical to solving the problems of poor economy and high cost of existing processes. Summary of the invention

[0009] In view of the problems of complex operation and high cost in the existing purification and purification of crude lithium carbonate to prepare battery-grade lithium carbonate, the present invention provides a method for purifying crude lithium carbonate to prepare battery-grade lithium carbonate with high feasibility and low cost.

[0010] In order to achieve the above object, the present invention is implemented by the following specific scheme:

[0011] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0012] (1) Sieving: Mix crude lithium carbonate with a certain amount of water, stir thoroughly, and then sieve to obtain a sieved material;

[0013] (2) slurry preparation: further diluting the screened material obtained in step (1), stirring and slurrying the material sufficiently to obtain a dispersed slurry;

[0014] (3) Pre-hydrogenation: introducing CO2 gas into the dispersed slurry obtained in step (2) to perform a pre-hydrogenation operation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0015] (4) Slurry treatment: adding a certain amount of lithium-containing reagent to the mixed slurry obtained in step (3), and heating the slurry to 50° C. to 95° C. under stirring to obtain a treated slurry;

[0016] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0017] (6) thermal decomposition: thermally decomposing the lithium bicarbonate solution obtained in step (5) at 90° C. to 100° C. to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0018] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0019] Moreover, the purity of the crude lithium carbonate is <98.5wt%, and the sulfate content in the crude lithium carbonate is >4000ppm, or the chlorine content is >400ppm, or the sodium content is >3000ppm, or the potassium content is >300ppm, or the calcium content is >500ppm, or the magnesium content is >1000ppm, or the barium content is >700ppm, or the boron content is >600ppm, or the above eight impurities are all exceeded.

[0020] Moreover, the sieving mesh number in step (1) is 100-300 mesh;

[0021] Moreover, after slurry adjustment in step (2), the mass ratio of lithium carbonate to water in the slurry is between 3:1 and 8:1. Preferably: the mass ratio of lithium carbonate to water in the slurry is between 3:1 and 5:1;

[0022] Moreover, the purity of CO2 in step (3) is >40%;

[0023] Moreover, the lithium-containing reagent in step (4) is LiOH, LiNO3 or Li2C2O4, and the added amount is 0-2% of the liquid phase;

[0024] Moreover, the thermal decomposition operation of step (6) can be selectively performed or not performed. If the content of Li2O in the lithium bicarbonate solution obtained in step (5) is greater than 5wt%, the thermal decomposition operation of step (6) is performed; if the content of Li2O in the lithium bicarbonate solution obtained in step (5) is less than 5wt%, the thermal decomposition operation of step (6) is not performed;

[0025] Moreover, the purity of the industrial grade wet lithium carbonate in step (7) is >98.5wt%; and the sulfate content in the industrial grade wet lithium carbonate is <3000ppm, the chlorine content is <300ppm, the sodium content is <2500ppm, the potassium content is <300ppm, the calcium content is <300ppm, the magnesium content is <20ppm, the barium content is <200ppm, and the boron content is <200ppm.

[0026] Compared with the existing method for purifying crude lithium carbonate to prepare battery-grade lithium carbonate, the present invention has the following beneficial effects:

[0027] (1) Pre-hydrogenation is performed at a low liquid-to-solid ratio, and it is not necessary to completely convert lithium carbonate into lithium bicarbonate, so the processing capacity is large;

[0028] (2) The low liquid-to-solid ratio results in a high enrichment of soluble impurity ions such as sulfate, chloride, sodium, and potassium in the mother liquor, which is easy to remove and recycle;

[0029] (3) The amount of reagent added to the system is extremely low, and the maximum amount of LiOH, LiNO3 or Li2C2O4 added does not exceed 2% of the liquid phase;

[0030] (4) Good removal effect of soluble impurities, avoiding contamination of lithium carbonate products by impurities in the liquid phase;

[0031] (5) The operation is simple and highly compatible with the existing process of preparing battery-grade lithium carbonate from industrial-grade lithium carbonate;

[0032] The above reasons are all important reasons why this process has good economy and high impurity removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The process flow chart of the method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate in the present invention;

[0034] Table 1 shows the purity and main impurity content of the crude lithium carbonate raw material in the embodiment of the present invention DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. However, the following embodiments are limited to explaining the present invention, and the protection scope of the present invention should include the entire content of the claims, not limited to the present embodiments.

[0036] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0037] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0038] The crude lithium carbonate used in all embodiments of the present invention comes from the same manufacturer and the same batch of raw materials, and its main components and impurity contents are as follows:

[0039]

[0040] Example 1

[0041] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0042] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0043] (2) Slurry preparation: After weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:3, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0044] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 50% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0045] (4) Slurry treatment: adding a LiOH reagent with a liquid content of 0.5% to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0046] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0047] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0048] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0049] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 1

[0050]

[0051] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 1

[0052]

[0053] Example 2

[0054] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0055] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 300-mesh sieve to obtain a sieved material;

[0056] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:4, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0057] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 50% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0058] (4) Slurry treatment: adding iOH reagent with a liquid content of 0.5% to the mixed slurry obtained in step (3), and heating the slurry to 65° C. under stirring to obtain a treated slurry;

[0059] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0060] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0061] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0062] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 2

[0063]

[0064]

[0065] The main component of industrial-grade wet lithium carbonate obtained in step 6 of Example 2

[0066]

[0067] Example 3

[0068] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0069] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0070] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:5, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0071] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 40% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0072] (4) Slurry treatment: adding a 1% LiOH reagent in liquid phase to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0073] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0074] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0075] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0076] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 3

[0077]

[0078] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 3

[0079]

[0080] Example 4

[0081] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0082] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0083] (2) Slurry preparation: After weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:3, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0084] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0085] (4) Slurry treatment: adding a LiOH reagent having a liquid content of 1% to the mixed slurry obtained in step (3), and heating the slurry to 70° C. under stirring to obtain a treated slurry;

[0086] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0087] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0088] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0089] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 4

[0090]

[0091] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 4

[0092]

[0093] Example 5

[0094] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0095] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0096] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:4, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0097] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0098] (4) Slurry treatment: adding a LiOH reagent with a liquid content of 0.5% to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0099] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0100] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0101] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0102] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 5

[0103]

[0104] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 5

[0105]

[0106] Example 6

[0107] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0108] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 300-mesh sieve to obtain a sieved material;

[0109] (2) Slurry preparation: After weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:3, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0110] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 50% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0111] (4) Slurry treatment: adding a 0.5% LiNO3 reagent in liquid phase to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0112] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0113] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0114] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0115] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 6

[0116]

[0117] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 6

[0118]

[0119] Example 7

[0120] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0121] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 300-mesh sieve to obtain a sieved material;

[0122] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:4, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0123] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 50% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0124] (4) Slurry treatment: adding a 1% LiNO3 reagent in liquid phase to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0125] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0126] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0127] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0128] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 7

[0129]

[0130] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 7

[0131]

[0132] Example 8

[0133] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0134] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 300-mesh sieve to obtain a sieved material;

[0135] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:5, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0136] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0137] (4) Slurry treatment: adding a 1% LiNO3 reagent in liquid phase to the mixed slurry obtained in step (3), and heating the slurry to 70° C. under stirring to obtain a treated slurry;

[0138] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0139] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0140] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0141] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 8

[0142]

[0143] The main component of industrial-grade wet lithium carbonate obtained in step 6 of Example 8

[0144]

[0145] Example 9

[0146] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0147] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0148] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:5, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0149] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0150] (4) Slurry treatment: adding a Li2C2O4 reagent having a liquid content of 0.5% to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0151] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0152] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0153] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0154] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 9

[0155]

[0156] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 9

[0157]

[0158] Example 10

[0159] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0160] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0161] (2) Slurry preparation: After weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:3, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0162] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 50% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0163] (4) Slurry treatment: adding a Li2C2O4 reagent having a liquid content of 0.5% to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0164] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0165] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0166] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is subjected to slurry mixing, hydrogenation, thermal decomposition, centrifugal filtration, and the filter cake is dried and crushed, and then tested to meet the product requirements of battery-grade lithium carbonate.

[0167] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 10

[0168]

[0169] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 10

[0170]

[0171] Embodiment 11

[0172] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0173] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 200-mesh sieve to obtain a sieved material;

[0174] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:4, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0175] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0176] (4) Slurry treatment: adding a Li2C2O4 reagent having a liquid content of 1% to the mixed slurry obtained in step (3), and heating the slurry to 70° C. under stirring to obtain a treated slurry;

[0177] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0178] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0179] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is slurried, hydrogenated, thermally decomposed, and centrifuged. The filter cake is dried and crushed, and tested to meet the product requirements of battery-grade lithium carbonate.

[0180] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 11

[0181]

[0182] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 11

[0183]

[0184] Example 12

[0185] A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate comprises the following steps:

[0186] (1) Sieving: Mix crude lithium carbonate with pure water at a solid-to-liquid ratio of 1:2, stir thoroughly, and pass through a 300-mesh sieve to obtain a sieved material;

[0187] (2) slurry preparation: after weighing the sieved material, pure water is added to the sieved material at a solid-liquid mass ratio of 1:5, and the mixture is fully stirred and slurried to obtain a dispersed slurry;

[0188] (3) Pre-hydrogenation: introducing a CO2 gas having a purity of 60% into the dispersed slurry obtained in step (2) for pre-hydrogenation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate;

[0189] (4) Slurry treatment: adding a Li2C2O4 reagent having a liquid content of 1% to the mixed slurry obtained in step (3), and heating the slurry to 60° C. under stirring to obtain a treated slurry;

[0190] (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution;

[0191] (6) Thermal decomposition: the lithium bicarbonate solution obtained in step (5) is continuously heated to 90° C. and kept at this temperature for 40 min to perform thermal decomposition to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate;

[0192] (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is slurried, hydrogenated, thermally decomposed, and centrifuged. The filter cake is dried and crushed, and tested to meet the product requirements of battery-grade lithium carbonate.

[0193] The main component of the industrial grade wet lithium carbonate obtained in step 5 of Example 12

[0194]

[0195] The main component of the industrial grade wet lithium carbonate obtained in step 6 of Example 12

[0196]

Claims

1. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate, comprising the following steps: (1) Sieving: Mix crude lithium carbonate with a certain amount of water, stir thoroughly, and then sieve to obtain a sieved material; (2) slurry preparation: further diluting the screened material obtained in step (1), stirring and slurrying the material sufficiently to obtain a dispersed slurry; (3) Pre-hydrogenation: introducing CO2 gas into the dispersed slurry obtained in step (2) to perform a pre-hydrogenation operation to obtain a mixed slurry containing a lithium bicarbonate solution and solid lithium carbonate; (4) Slurry treatment: adding a certain amount of lithium-containing reagent to the mixed slurry obtained in step (3), and heating the slurry to 50° C. to 95° C. under stirring to obtain a treated slurry; (5) liquid-solid separation: subjecting the treated slurry obtained in step (4) to liquid-solid separation, wherein the solid phase is industrial-grade wet lithium carbonate and the liquid phase is a lithium bicarbonate solution; (6) thermal decomposition: thermally decomposing the lithium bicarbonate solution obtained in step (5) at 90° C. to 100° C. to obtain lithium carbonate slurry, which is then filtered to obtain mother liquor and industrial-grade wet lithium carbonate; (7) Purification: The industrial-grade wet lithium carbonate obtained in step (5) and step (6) is slurried, hydrogenated, thermally decomposed, and centrifuged. The filter cake is dried and crushed, and tested to meet the product requirements of battery-grade lithium carbonate.

2. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The purity of the crude lithium carbonate is <98.5wt%, and the sulfate content in the crude lithium carbonate is >4000ppm, or the chlorine content is >400ppm, or the sodium content is >3000ppm, or the potassium content is >300ppm, or the calcium content is >500ppm, or the magnesium content is >1000ppm, or the barium content is >700ppm, or the boron content is >600ppm, or all eight impurities mentioned above exceed the standard.

3. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The sieving mesh number described in step (1) is 100-300 meshes.

4. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: After slurry adjustment in step (2), the mass ratio of lithium carbonate to water in the slurry is between 1:3 and 1:

8. Preferably, the mass ratio of lithium carbonate to water in the slurry is between 1:3 and 1:

5.

5. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The CO2 purity in step (3) is >40%.

6. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The lithium-containing reagent in step (4) is LiOH, LiNO3 or Li2C2O4, and the added amount is 0-2% of the liquid phase.

7. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The thermal decomposition operation of step (6) can be selectively performed or not performed. If the content of Li2O in the lithium bicarbonate solution obtained in step (5) is greater than 5wt%, the thermal decomposition operation of step (6) is performed; if the content of Li2O in the lithium bicarbonate solution obtained in step (5) is less than 5wt%, the thermal decomposition operation of step (6) is not performed.

8. A method for preparing battery-grade lithium carbonate by purifying crude lithium carbonate according to claim 1, characterized in that: The industrial grade wet lithium carbonate of step (7) has a purity of >98.5wt%; and the industrial grade wet lithium carbonate has a sulfate content of <3000ppm, a chlorine content of <300ppm, a sodium content of <2500ppm, a potassium content of <300ppm, a calcium content of <300ppm, a magnesium content of <20ppm, a barium content of <200ppm, and a boron content of <200ppm.

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