Preparation method and application of battery-grade lithium hydroxide

Abstract

The present application discloses a preparation method and application of battery-grade lithium hydroxide, the preparation method comprising the following steps: S100, obtaining a mixed solution of lithium chloride, alkali metal hydroxide and alcohol composite solvent, performing an alkalization lithium precipitation reaction, filtering, and obtaining lithium hydroxide solid and filtrate, S200, countercurrent washing, drying and crystallizing the lithium hydroxide solid to obtain battery-grade lithium hydroxide, and the alcohol composite solvent comprises an alcohol compound and water. The present application adopts an alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride, which can significantly improve the yield of battery-grade lithium hydroxide, and the process flow is simple and easy to industrialize.

Description

Technical Field

[0001] The present application relates to the technical field of battery materials, and in particular to a method for preparing battery-grade lithium hydroxide and its application. Background Art

[0002] The demand for lithium hydroxide has risen in tandem with the growth of the demand for high-nickel ternary power batteries. The current common process for preparing lithium hydroxide in the industry is the lithium carbonate causticization method, that is, lithium carbonate and calcium hydroxide are mixed and heated, and then filtered and washed to remove calcium carbonate to obtain lithium hydroxide mother liquor, which is then evaporated, crystallized, washed, and dried to obtain lithium hydroxide products. However, the excess calcium hydroxide dissolved in the mother liquor is difficult to remove, and the product has the problem of excessive calcium content.

[0003] The prior art discloses a method for preparing lithium hydroxide, which comprises reacting an alkali solution with a lithium chloride-containing brine to generate dissolved lithium hydroxide and precipitated lithium hydroxide, and then filtering, washing and drying the precipitated lithium hydroxide to obtain a finished lithium hydroxide. Since the solubility of lithium hydroxide in water is about 12.4 g / 100 g, the yield of the finished lithium hydroxide does not exceed 20%. Summary of the invention

[0004] In view of this, the present application provides a preparation method of battery-grade lithium hydroxide and its application, which uses an alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride, can significantly improve the yield of battery-grade lithium hydroxide, and the process flow is simple and easy to industrialize.

[0005] In the first aspect, the present application provides a method for preparing battery-grade lithium hydroxide, the preparation method comprising the following steps: S100, obtaining a mixed solution of lithium chloride, alkali metal hydroxide and alcohol composite solvent, performing an alkalization lithium precipitation reaction, filtering, and obtaining lithium hydroxide solid and filtrate, S200, countercurrent washing, drying and crystallizing the lithium hydroxide solid to obtain battery-grade lithium hydroxide. Among them, the alcohol composite solvent includes alcohol compounds and water. The present application adopts an alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride, and the solubility of the product battery-grade lithium hydroxide in the above-mentioned alcohol composite solvent can be reduced to as low as 1.88g / 100g, see Figure 1 (Taking the composite binary solvent of water and ethanol as an example), compared with the solubility of lithium hydroxide in water of 12.4g / 100g in the prior art, the significant reduction in the solubility of lithium hydroxide in the alcohol composite solvent in the present application can significantly increase the yield of battery-grade lithium hydroxide, see Figure 2 , Figure 2 yes Figure 1The yield corresponding to the corresponding solubility of the product lithium hydroxide can be seen, and the yield of this application can reach up to 52.9%. Therefore, this application uses alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride, which can significantly improve the yield of the product battery-grade lithium hydroxide.

[0006] In some embodiments, the preparation method further comprises the following steps: S300, adding a precipitant containing carbonate or passing carbon dioxide into the filtrate, performing carbonization and precipitation reaction, filtering, obtaining lithium carbonate solid, S400, lithium carbonate solid after washing and drying, obtaining finished lithium carbonate. The inventor unexpectedly found that when the alcohol composite solvent in step S100 is continued as the reaction environment of carbonization and precipitation reaction in step S300, the solubility of the byproduct lithium carbonate is also significantly reduced, about 0.3g / 100g (i.e., 100g of alcohol composite solvent only dissolves 0.3g lithium carbonate), compared with the solubility of lithium carbonate 1.32g / 100g pure water, the solubility decreases by about 77.3%. The reduction in the solubility of lithium carbonate in alcohol composite solvents can significantly improve the yield of lithium on the one hand, and can also improve the purity of byproduct dissolved salts (sodium chloride or potassium chloride, etc.) on the other hand. Wherein, the byproduct dissolved salt is the chloride obtained by neutralizing the mother liquor after carbonization and precipitation reaction with hydrochloric acid and evaporating and crystallizing. It can be seen that in the preparation method of the present application, the alcohol composite solvent can be used not only as the reaction environment of the alkalization lithium precipitation reaction, but also as the reaction environment of the carbonization lithium precipitation reaction, and accordingly, not only the yield of the main product lithium hydroxide is improved, but also very good effects are brought to the by-products, that is, high-purity lithium carbonate can be obtained, and the overall yield of lithium element is further improved, and high-purity dissolved salt can also be obtained. In other words, the present application uses the same composite solvent (alcohol composite solvent) in the overall process, which has a beneficial effect on the main product lithium hydroxide and the by-product (lithium carbonate and dissolved salt), and there is no need to add new other solvents in the process of preparing and / or extracting the product, simplifying the process steps, reducing the introduction of impurities, and the high-purity lithium carbonate and high-purity salt of the by-product can also be sold as products.

[0007] In some embodiments, the alcohol compound includes at least one of a low-carbon monohydric alcohol, a low-carbon dihydric alcohol or a low-carbon polyhydric alcohol, the low-carbon monohydric alcohol is selected from any one of C1 to C4 monohydric alcohols, the low-carbon dihydric alcohol is selected from any one of C1 to C4 dihydric alcohols, and the low-carbon polyhydric alcohol is selected from any one of C1 to C4 polyhydric alcohols. Preferably, the low-carbon monohydric alcohol includes any one of methanol, ethanol, and isopropanol, the low-carbon dihydric alcohol includes ethylene glycol and / or propylene glycol, and the low-carbon polyhydric alcohol includes glycerol and / or trimethylolpropane. The present application selects low-carbon (carbon number 1 to 4) alcohol compounds, especially the above-mentioned types of low-carbon monohydric alcohols, low-carbon dihydric alcohols and low-carbon trihydric alcohols, which is more conducive to improving the yield of the product battery-grade lithium hydroxide and the overall yield of lithium element.

[0008] In some embodiments, based on the total mass of the alcohol composite solvent, the mass percentage of the alcohol compound is n, 30wt%≤n≤60wt%. Preferably, 35wt%≤n≤55wt%. When the mass percentage of the alcohol compound is regulated within the above range, it is beneficial to improve the yield of lithium hydroxide and can simultaneously improve the overall yield of lithium element. Figure 2 See also Figure 3 As shown, when the ethanol content is 30wt% to 60wt%, the solubility of lithium carbonate is about 0.3g / 100g alcohol composite solvent. Compared with the solubility of 1.32g / 100g pure water, the solubility of lithium carbonate decreases by 77.3%. The reduction of lithium carbonate solubility in alcohol composite solvents can increase the total yield of lithium element and the purity of dissolved salts in by-products. At the same time, surprisingly, when the mass proportion of alcohol compounds in alcohol composite solvents is in the range of 35wt% to 55wt%, the solubility of the corresponding lithium hydroxide and lithium carbonate in the composite solvent is very low, and lithium hydroxide and lithium carbonate can be effectively extracted at the same time, thereby increasing the overall yield of lithium element.

[0009] In some embodiments, the alcohol composite solvent is a composition of an alcohol compound and water. This is more conducive to improving the yield of the main product lithium hydroxide and the overall yield of lithium element.

[0010] In some embodiments, in step S100, the mass of the alcohol composite solvent is W, and the sum of the masses of lithium chloride and alkali metal hydroxide is W', satisfying: W:W'=1:(0.1-0.3). Preferably, W:W'=1:(0.13-0.26). The proportion of the alcohol composite solvent in the reaction system is appropriate, which is conducive to further improving the yield of the product lithium hydroxide and the overall yield of lithium element.

[0011] In some embodiments, in step S100, the mass ratio of lithium chloride to alkali metal hydroxide is 0.7 to 1.16. Preferably, the mass ratio of lithium chloride to alkali metal hydroxide is 1.03 to 1.08. The appropriate mass ratio of lithium chloride to alkali metal hydroxide is conducive to the forward reaction and further improves the yield of the main product, battery-grade lithium hydroxide.

[0012] In some embodiments, in step S100, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 10°C to 99°C, a reaction time of 0.1min to 20min, and a reaction speed of 150r / min to 300r / min. Preferably, the reaction temperature is 25°C to 95°C, the reaction time is 2min to 10min, and the alkalization lithium precipitation reaction speed is 180r / min to 220r / min. The reaction system containing lithium chloride, alkali metal hydroxide and alcohol composite solvent is more conducive to the alkalization lithium precipitation reaction under the above reaction conditions, and further improves the yield of the main product lithium hydroxide. In some embodiments, in step S100, the alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide. Sodium hydroxide and / or potassium hydroxide are more conducive to the forward progress of the alkalization lithium precipitation reaction, further improving the yield of the product lithium hydroxide.

[0013] In some embodiments, when 30% ≤ n ≤ M%, the reaction temperature of alkalization and lithium precipitation is 10-35 ° C, and when M% < n ≤ 60%, the reaction temperature of alkalization and lithium precipitation is 50-95 ° C, wherein the value range of M is 47 ≤ M ≤ 48. When the mass proportion of alcohol compounds is in the interval of 30% ≤ n ≤ M%, it can be regarded as that the proportion of alcohol compounds in the alcohol composite solvent is small, and the reaction at room temperature can avoid reducing the yield of lithium hydroxide, and the reaction can react rapidly at room temperature, and the reaction at room temperature does not require heating or cooling, which helps to reduce the energy consumption of the whole process. When the proportion of alcohol compounds is in the interval of M% < n ≤ 60%, it can be regarded as that the proportion of alcohol compounds in the alcohol composite solvent is large. At this time, the higher reaction temperature can regulate the proportion of alcohol compounds in the appropriate range (appropriately lower the proportion of alcohol compounds), so as to improve the yield of lithium hydroxide and improve the overall yield of lithium element. M is the proportion of organic solvent corresponding to the extreme value in the alcohol composite solvent-lithium hydroxide yield curve. For example, for an alcohol composite solvent composed of ethanol and water, M is 47.6. When 30%≤n≤47.6%, the reaction temperature of the alkalization lithium precipitation stage is 10-35°C. When 47.6%<n≤60%, the reaction temperature of the alkalization lithium precipitation stage is 50-95°C. The corresponding lithium hydroxide yield can reach more than 40%. See Figure 2 .

[0014] Preferably, when 35%≤n≤M%, the reaction temperature of the alkalization lithium precipitation stage is 10-35°C, and when M%<n≤55%, the reaction temperature of the alkalization lithium precipitation stage is 50-95°C. In this way, the yield of the corresponding lithium hydroxide can reach more than 48%, and the solubility of lithium carbonate corresponding to this region is also low (about 0.3g / 100g alcohol composite solvent), and the total yield of lithium element is high.

[0015] For example, when the alcohol composite solvent is a composition of an alcohol compound and water, when 35%≤n≤47.6%, the reaction temperature of the alkalization lithium precipitation stage is 10-35°C, and when 47.6%<n≤55%, the reaction temperature of the alkalization lithium precipitation stage is 50-95°C. At this time, the maximum yield of the product lithium hydroxide can reach 52.9%, which is a great improvement compared to the maximum yield of 16.6% using only water as a solvent.

[0016] In some embodiments, in step S200, the solution of the countercurrent washing includes a saturated lithium hydroxide solution, the number of countercurrent washings is 3 to 10 times, the temperature of the drying crystallization is 180° C. to 250° C., and the pressure is 0.01 MPa to 0.1 MPa. In this way, the obtained battery-grade lithium hydroxide can be directly sold as a product.

[0017] In some embodiments, in step S300, the precipitating agent includes sodium carbonate and / or potassium carbonate.

[0018] In some embodiments, in step S300, when carbon dioxide is introduced into the first filtrate, the carbonization and lithium precipitation reaction further includes: pyrolyzing the reaction solution at 75° C. to 95° C. for 2 h to 4 h, and then filtering. If a carbonate-containing precipitant is added in step S300, the lithium carbonate precipitate can be directly filtered out after the reaction is completed.

[0019] In some embodiments, in step S100, obtaining a mixed solution of lithium chloride, alkali metal hydroxide and alcohol composite solvent includes: dissolving lithium chloride in water and dissolving alkali in alcohol compound, and then mixing the two; or dissolving lithium chloride in alcohol compound and dissolving alkali in water, and then mixing the two. In this way, alkali and lithium chloride react with each other in liquid-liquid state, the reaction contact area is large, the reaction is rapid, and the product lithium hydroxide precipitates to the bottom with fine and uniform particles.

[0020] In a second aspect, the present application provides battery-grade lithium hydroxide prepared by any one of the preparation methods of the first aspect above.

[0021] In a third aspect, the present application provides the use of battery-grade lithium hydroxide prepared by any one of the preparation methods of the first aspect in a ternary power battery.

[0022] The present application adopts an alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride, so that the solubility of the product lithium hydroxide in the alcohol composite solvent is significantly reduced, and the lowest can be reduced to 1.88g / 100g alcohol composite solvent. According to calculations, the yield of the product lithium hydroxide in the present application can reach more than 40%, and the highest can reach 52.9%. Compared with the yield of 16.4% when only water is used as a solvent, the yield of lithium hydroxide is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a schematic diagram of the solubility change of lithium hydroxide in an alcohol composite solvent in this application;

[0025] Figure 2 This is a schematic diagram of the change in the yield of lithium hydroxide in an alcohol composite solvent in this application;

[0026] Figure 3 This is a schematic diagram of the solubility change of lithium carbonate in alcohol composite solvents in this application;

[0027] Figure 4 This is a schematic diagram of the process flow of the method for preparing battery-grade lithium hydroxide in this application;

[0028] Figure 5 This is a product photo of the lithium hydroxide prepared in Example 1 of this application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0030] In the prior art, alkali solution is reacted with lithium chloride-containing brine to generate dissolved lithium hydroxide and precipitated lithium hydroxide, and the precipitated lithium hydroxide is filtered, washed, and dried to obtain finished lithium hydroxide. Since lithium hydroxide has a large solubility in water, about 12.4g / 100g water, a large solubility will cause the problem of low lithium hydroxide yield. Taking the alkali solution as sodium hydroxide and 100g water dissolution as an example, when the generated sodium chloride saturated precipitate is only lithium hydroxide, the total lithium hydroxide mass generated is 14.83g. At this time, 12.4g of lithium hydroxide is dissolved in 100g water, and the precipitated lithium hydroxide that can be filtered, washed, and dried is only 2.43g, that is, the yield W=2.43 / (2.43+12.4)×100=16.4%, that is, the lithium hydroxide yield of this method is only 16.4%. In addition, the lithium carbonate generated by dissolving part of the lithium hydroxide (lithium hydroxide in the filtrate) after adding the precipitant still has a solubility of 1.32g / 100g water in water. After filtration, the lithium carbonate cannot be completely separated from the dissolved salt, resulting in a reduced lithium recovery rate and the recovered dissolved salt is doped with lithium carbonate impurities and cannot be sold directly. Therefore, the present application provides a method for preparing battery-grade lithium hydroxide to solve the above technical problems.

[0031] Preparation method of battery grade lithium hydroxide

[0032] like Figure 4 As shown, it includes the following steps: S100, obtain a mixed solution of lithium chloride, alkali metal hydroxide and alcohol composite solvent, carry out alkalization lithium precipitation reaction, filter, and obtain lithium hydroxide solid and filtrate. S200, countercurrent wash, dry and crystallize the lithium hydroxide solid to obtain battery-grade lithium hydroxide, wherein the alcohol composite solvent includes alcohol compounds and water. S300, add a carbonate-containing precipitant to the filtrate or pass carbon dioxide to carry out carbonization lithium precipitation reaction, filter, and obtain lithium carbonate solid and a second filtrate. S400, after washing and drying the lithium carbonate solid, the finished lithium carbonate is obtained, and the second filtrate is neutralized with hydrochloric acid aqueous solution (the mass percentage of hydrochloric acid in the hydrochloric acid aqueous solution is 8% to 10%), evaporated and crystallized to obtain chloride (dissolved salt). The present application utilizes the same composite solvent (alcohol composite solvent) as the reaction environment for the alkalization lithium precipitation reaction and the carbonization lithium precipitation reaction in the overall process, which not only improves the yield of the main product lithium hydroxide, but also brings very good effects on the by-products. For example, high-purity lithium carbonate can be obtained, the overall yield of lithium elements can be improved, and high-purity dissolved salts can be obtained.

[0033] In the above step S100, lithium chloride and alkali metal hydroxide can be directly added to an alcohol composite solvent to carry out an alkalization lithium precipitation reaction, or they can be dissolved separately in water and / or an alcohol compound as corresponding solutions and then mixed to carry out an alkalization lithium precipitation reaction. Specifically, in the present application, an alcohol composite solvent can be first configured, and then lithium chloride and alkali are added to the configured alcohol composite solvent. Alternatively, lithium chloride can be dissolved in water (or an organic solvent), and the alkali can be dissolved in an alcohol compound (or water), and then the two can be mixed. Alternatively, lithium chloride and alkali can be dissolved in water at the same time, and then an alcohol compound can be added. Alternatively, lithium chloride and alkali can be dissolved in an alcohol compound at the same time, and then water can be added. The present application does not limit this, and can be specifically selected according to actual process conditions. Among them, a better way is to dissolve lithium chloride in water (or an alcohol compound) and dissolve the alkali in an alcohol compound (or water), and then mix the two. In this way, the alkali and lithium chloride react with each other in a liquid-liquid state, the reaction contact area is large, the reaction is rapid, and the product lithium hydroxide precipitates to the bottom with fine and uniform particles, as shown. Figure 5 shown.

[0034] In some embodiments, the alcohol compound includes at least one of a low-carbon monohydric alcohol, a low-carbon dihydric alcohol or a low-carbon polyhydric alcohol, the low-carbon monohydric alcohol is selected from any one of C1 to C4 monohydric alcohols, the low-carbon dihydric alcohol is selected from any one of C1 to C4 dihydric alcohols, and the low-carbon polyhydric alcohol is selected from any one of C1 to C4 polyhydric alcohols. Low-carbon monohydric alcohols include any one of methanol, ethanol, and isopropanol, low-carbon dihydric alcohols include ethylene glycol and / or propylene glycol, and low-carbon polyhydric alcohols include glycerol and / or trimethylolpropane. Specifically, in some examples, the low-carbon monohydric alcohol includes ethanol. In other examples, the low-carbon monohydric alcohol includes ethanol and may also include methanol and / or isopropanol. The above-mentioned types of low-carbon monohydric alcohols, low-carbon dihydric alcohols and low-carbon trihydric alcohols are more conducive to improving the total yield of lithium hydroxide and the yield of lithium hydroxide.

[0035] In some embodiments, based on the total mass of the alcohol composite solvent, the mass percentage of the alcohol compound is n, 30wt%≤n≤60wt%. In some embodiments, 35wt%≤n≤55wt%. In some embodiments, 40wt%≤n≤55wt%. In some embodiments, 45wt%≤n≤55wt%. The proportion of alcohol compounds is within the above range, which is more conducive to improving the yield of lithium hydroxide while taking into account the overall yield of lithium element. Exemplarily, the mass percentage n of the alcohol compound is 30wt%, 33wt%, 35wt%, 38wt%, 40wt%, 45wt%, 48wt%, 50wt%, 53wt%, 55wt%, 58wt%, 60wt% or a value within the range composed of any two of these values.

[0036] In some embodiments, the mass of the alcohol composite solvent is W, and the sum of the masses of lithium chloride and alkali metal hydroxide is W', satisfying: W:W'=1:(0.1-0.3). In some embodiments, W:W'=1:(0.13-0.26). In some embodiments, W:W'=1:(0.15-0.23). The mass proportion of the alcohol composite solvent in the reaction system is appropriate, which is more conducive to improving the yield of the product lithium hydroxide and the overall yield of the lithium element. Exemplarily, the ratio of W:W' is 1:0.1, 1:0.13, 1:0.15, 1:0.18, 1:0.2, 1:0.23, 1:0.26, 1:0.28, 1:0.3 or a value within the range composed of any two of these values.

[0037] In some embodiments, the mass ratio of lithium chloride to alkali metal hydroxide is 0.7 to 1.16. In some embodiments, the mass ratio of lithium chloride to alkali metal hydroxide is 1.03 to 1.08. The mass ratio of lithium chloride to alkali metal hydroxide is within the above range, which is conducive to further improving the yield of the main product lithium hydroxide. Exemplarily, the mass ratio of lithium chloride to alkali metal hydroxide is 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, 1.03, 1.05, 1.08, 1.1, 1.13, 1.15, 1.16 or a value within the range composed of any two of these values.

[0038] In some embodiments, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 10°C to 99°C, a reaction time of 0.1min to 20min, and a reaction speed of 150r / min to 300r / min. When the conditions of the alkalization lithium precipitation reaction meet the above range, it is more conducive to the alkalization lithium precipitation reaction, and further improves the yield of the main product lithium hydroxide. Exemplarily, the reaction temperature is 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 45°C, 55°C, 65°C, 75°C, 85°C, 95°C, 99°C or a value within the range of any two of these values. Exemplarily, the reaction time is 0.1min, 0.5min, 1min, 2min, 5min, 8min, 10min, 15min, 18min, 20min or a value within the range of any two of these values. Exemplarily, the reaction speed is 150 r / min, 160 r / min, 180 r / min, 200 r / min, 210 r / min, 220 r / min, 260 r / min, 300 r / min or a value within the range formed by any two of these values.

[0039] In some embodiments, the alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide. Sodium hydroxide and / or potassium hydroxide are more conducive to the positive progress of the alkalization lithium precipitation reaction, further improving the yield of the product lithium hydroxide.

[0040] In some embodiments, when 30%≤n≤M%, the reaction temperature of alkalization and lithium precipitation is 10-35°C. When M%<n≤60%, the reaction temperature of alkalization and lithium precipitation is 50-95°C, and the value range of M is 47≤M≤48. In some embodiments, when 35%≤n≤M%, the reaction temperature of the alkalization and lithium precipitation stage is 10-35°C. When M%<n≤55%, the reaction temperature of the alkalization and lithium precipitation stage is 50-95°C. In some embodiments, when the alcohol composite solvent is a composition of an alcohol compound and water, when 30%≤n≤47.6%, the reaction temperature of the alkalization and lithium precipitation stage is 10-35°C, and when 47.6%<n≤60%, the reaction temperature of the alkalization and lithium precipitation stage is 50-95°C. In this way, regulating the mass proportion of alcohol compounds in an appropriate range can not only help to improve the yield of lithium hydroxide, but also take into account the overall yield of lithium elements.

[0041] In some embodiments, in step S200, the solution of the countercurrent washing includes a saturated lithium hydroxide solution, the number of countercurrent washings is 3 to 10 times, the temperature of the drying crystallization is 180°C to 250°C, and the pressure is 0.01MPa to 0.1MPa. Exemplarily, in some embodiments, the number of countercurrent washings is 3 times, 4 times, 5 times, 6 times, 8 times, 10 times, or a value in the range of any two of these values. In some embodiments, the temperature of the drying crystallization is 180°C, 200°C, 210°C, 230°C, 245°C, 250°C, or a value in the range of any two of these values. In some embodiments, the pressure is 0.01MPa, 0.03MPa, 0.05MPa, 0.08MPa, 0.1MPa, or a value in the range of any two of these values.

[0042] In some embodiments, in step S300, the precipitant includes sodium carbonate and / or potassium carbonate, and the molar ratio of the precipitant to the lithium hydroxide dissolved in the filtrate is 1:(2-2.2). Exemplarily, the molar ratio of the precipitant to the lithium hydroxide dissolved in the filtrate is 1:2, 1:2.05, 1:2.1, 1:2.15, 1:2.2, or a value within the range consisting of any two of these values.

[0043] In some embodiments, in step S300, when carbon dioxide is introduced into the filtrate, the carbonization and lithium precipitation reaction further includes: pyrolyzing the reaction solution at 75°C to 95°C for 2h to 4h, and then filtering. This is more conducive to improving the overall yield of lithium elements.

[0044] In some embodiments, in step S400, the drying temperature is 120° C. to 250° C. In this way, finished lithium carbonate that can be directly sold can be obtained.

[0045] The following are possible implementations

[0046] The main purpose of the present invention is to provide a method for producing battery-grade lithium hydroxide using lithium chloride as a raw material, aiming to solve the problems of low lithium hydroxide yield, low purity, low lithium yield and the like in the prior art solutions.

[0047] To achieve the above object, the present invention provides a method for producing battery-grade lithium hydroxide using lithium chloride as a raw material, which comprises the following steps:

[0048] S1, adding lithium chloride and alkali into a composite solvent to perform an alkalization lithium precipitation reaction, and filtering out the lithium hydroxide precipitate after the reaction is completed.

[0049] S2, washing the filtered lithium hydroxide in a countercurrent manner, evaporating and crystallizing to prepare battery-grade lithium hydroxide.

[0050] Furthermore, the following steps are also included:

[0051] S3, adding a carbonate-containing precipitant to the filtrate from which the lithium hydroxide precipitate is filtered out, or introducing carbon dioxide to carbonize and precipitate the lithium. If the reaction of adding a carbonate-containing precipitant is completed, the lithium carbonate precipitate can be filtered out. If carbon dioxide gas is introduced as a precipitant, the solution needs to be pyrolyzed at 75 to 95° C. for 2 to 4 hours before the lithium carbonate precipitate is filtered out.

[0052] S4, washing the filtered lithium carbonate in countercurrent, drying and crystallizing to prepare battery-grade lithium carbonate.

[0053] S5, the filtrate is neutralized by adding hydrochloric acid, evaporated and crystallized, and countercurrent washed to obtain high-purity salt.

[0054] Furthermore, in the above step S1, the composite solvent comprises a composite solvent composed of water and an organic solvent, the organic solvent is an alcohol compound, and the alcohol compound is selected from at least one of a monohydric alcohol, a dihydric alcohol, and a polyhydric alcohol;

[0055] Among them, the role of water is to promote the dissolution of high-purity salt, and alcohol organic matter can reduce the dissolution of lithium hydroxide / lithium carbonate.

[0056] Furthermore, in the above step S1, the mass proportion of the organic solvent in the composite solvent is in the range of 5% to 65%, and the preferred range is 30% to 60%, and the corresponding lithium hydroxide yield can reach more than 40%. The further preferred area is 35% to 55%, and the corresponding lithium hydroxide yield can reach more than 48%, and the corresponding lithium carbonate solubility in this area is also low (about 0.3g / 100g solvent), and the overall yield of lithium element is high.

[0057] Furthermore, in the above step S1, the lithium chloride and the alkali can be added to the composite solvent separately for the alkalinization lithium precipitation reaction, or they can be dissolved separately in water and / or organic matter as corresponding solutions and then mixed for the alkalinization lithium precipitation reaction, wherein the composite solvent acts as a reaction site. For example, in this process, the composite solvent can be first configured, and then the lithium chloride and the alkali are added to the configured composite solvent, or the lithium chloride can be dissolved in water (or an organic solvent), and the alkali can be dissolved in an organic solvent (or water), and then the two can be mixed, or the lithium chloride and the alkali can be dissolved in water at the same time, and then an organic solvent is added, or the lithium chloride and the alkali can be dissolved in an organic solvent at the same time, and then water is added.

[0058] Among them, a better way is to dissolve lithium chloride in water (or an organic solvent), dissolve alkali in an organic solvent (or water), and then mix the two. In this way, the alkali and lithium chloride react with each other in a liquid-liquid state, the reaction contact area is large, the reaction is rapid, and the product lithium hydroxide settles to the bottom with fine and uniform particles.

[0059] Furthermore, in the above step S1, the optimal mass ratio of lithium chloride to alkali is 0.7 to 1.16, wherein the preferred optimal mass ratio is 1.03 to 1.08, within which the lithium chloride and alkali react more fully.

[0060] Furthermore, in the above step S1, the reaction temperature is 10°C to 99°C, and the reaction time is 0.1 min to 20 min. The preferred reaction time is 2 to 10 min, and a shorter reaction time is helpful to improve the utilization rate of the equipment.

[0061] Preferably, in this process, the mass proportion of the organic solvent in the composite solvent is n,

[0062] When 30%≤n≤M%, the reaction temperature in the alkalization lithium precipitation stage is 10-35°C;

[0063] When M%<n≤60%, the reaction temperature of the alkalization lithium precipitation stage is 50~95℃;

[0064] The value range of M is 47≤M≤48.

[0065] When the organic solvent accounts for a small proportion in the composite solvent when the organic solvent accounts for 30% ≤ n ≤ M%, the reaction can be carried out at room temperature to avoid the volatilization of ethanol and reduce the yield of lithium hydroxide. Moreover, the reaction can be carried out quickly at room temperature, and the reaction at room temperature does not require heating or cooling, which helps to reduce the energy consumption of the entire process. When the organic solvent accounts for a large proportion in the composite solvent when the organic solvent accounts for M% < n ≤ 60%, the organic solvent accounts for a large proportion in the composite solvent. At this time, the organic solvent can be volatilized by a higher reaction temperature, reducing the organic solvent ratio n value. Figure 2 and Figure 3, which is beneficial to improve the yield of lithium hydroxide and the overall yield of lithium element. M is the proportion of organic solvent corresponding to the extreme value in the alcohol composite solvent-lithium hydroxide yield curve (horizontal axis). For example, for a mixed solvent composed of ethanol and water, M = 47.6. At this time: when 30% ≤ n ≤ 47.6%, the reaction temperature of the alkalization lithium precipitation stage is 10-35°C; when 47.6% < n ≤ 60%, the reaction temperature of the alkalization lithium precipitation stage is 50-95°C.

[0066] Further preferably, in order to achieve a higher yield of lithium hydroxide and lithium carbonate, the n value and the reaction temperature can be adjusted within the following range:

[0067] 35%≤n≤M%, the reaction temperature in the alkalization lithium precipitation stage is 10~35℃;

[0068] M%<n≤55%, the reaction temperature of the alkalization lithium precipitation stage is 50~95℃;

[0069] The value range of M is 47≤M≤48.

[0070] Furthermore, the alkalization and lithium precipitation process in the above step S1 can be stirred simultaneously, and the stirring speed is 50 to 2000 r / min.

[0071] Furthermore, in the above step S1, the alkali is sodium hydroxide or potassium hydroxide.

[0072] Furthermore, the number of countercurrent washing in the above step S2 is 1 to 10 times, and a saturated lithium hydroxide solution can be used for washing.

[0073] Furthermore, in the above step S2, the temperature of the evaporation crystallization is 40-250° C., and the pressure is 0-0.1 MPa.

[0074] Furthermore, in the above step S3, the precipitant is sodium carbonate or potassium carbonate or carbon dioxide.

[0075] Furthermore, in the above step S3, the optimal molar ratio of the precipitant to the lithium hydroxide dissolved in the solution is 1:(2-2.2).

[0076] Furthermore, the carbonization and lithium precipitation process in the above step S3 can be stirred simultaneously, and the stirring speed is 50 to 2000 r / min.

[0077] Furthermore, the number of countercurrent washing in the above step S4 is 1 to 10 times.

[0078] Furthermore, in the above step S4, the temperature of the drying crystallization is 40 to 250° C., and the pressure is 0 to 0.1 MPa.

[0079] Furthermore, the number of countercurrent washing in the above step S5 is 1 to 10 times.

[0080] Furthermore, in the above step S5, the temperature of evaporation and crystallization is 40-250° C., and the pressure is 0-0.1 MPa. The distillate can be returned to the alkalization and lithium precipitation step and continued to be used after adjusting the ratio.

[0081] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Unless otherwise stated, the parts, percentages and ratios listed are all based on mass.

[0082] Example 1

[0083] <Example when the ethanol content is 47.6%>

[0084] Step 1: Weigh 9.07g of LiCl solid and dissolve it in 47.6g of ethanol solution, weigh 8.56g of sodium hydroxide solid and dissolve it in 52.4g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of ethanol in the alcohol composite solvent is 47.6%, and the aqueous solution containing sodium hydroxide and the ethanol solution containing lithium chloride are mixed at 25°C to perform an alkalization lithium precipitation reaction, the reaction time is 5min, stirring is added to the lithium precipitation reaction, the rotation speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0085] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 2.71 g of lithium hydroxide with a purity of 99.95%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 5.12 g of lithium hydroxide was generated by the reaction, and the lithium hydroxide yield of this group of experiments was W1 = (2.71 × 0.9995) / 5.12 × 100 = 52.9%.

[0086] Step 3: Add 5.33 g of sodium carbonate to the above filtrate to carbonize lithium (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), stir the reaction of carbonizing lithium, and the speed is 200 r / min. After the carbonization of lithium is completed, filter to obtain lithium carbonate solid and the second filtrate.

[0087] Step 4: Wash the lithium carbonate solid in reverse flow for 3 times, and vacuum evaporate and dry at 120°C and normal pressure to obtain 3.4g of lithium carbonate with a purity of 99.87%. Add 23.24g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 15.3g of sodium chloride with a purity of 98%.

[0088] The mass of lithium chloride input this time is 9.07g, and the lithium equivalent is 1.485g. 2.71g of lithium hydroxide with a purity of 99.95% is generated, and the lithium equivalent is 0.777g. 3.4g of lithium carbonate with a purity of 99.87% is generated, and the lithium equivalent is 0.638g. The lithium yield of this group of experiments is Q1=(0.777+0.638) / 1.485×100=95.3%.

[0089] Example 2

[0090] <Example when the ethanol content is 35%>

[0091] Step 1: Weigh 12.96g of LiCl solid and dissolve it in 35g of ethanol solution, weigh 12.22g of sodium hydroxide solid and dissolve it in 65g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of ethanol in the alcohol composite solvent is 35%, and the aqueous solution of sodium hydroxide and the ethanol solution of lithium chloride are mixed at 25°C for alkalization and lithium precipitation. The reaction time is 10min, stirring is added to the lithium precipitation reaction, the rotation speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0092] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 3.51 g of lithium hydroxide with a purity of 99.99%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 7.32 g of lithium hydroxide was generated by the reaction, and the lithium hydroxide yield of this group of experiments was W2 = (3.51 × 0.9999) / 7.32 × 100 = 47.95%.

[0093] Step 3: Add 8.43 g of sodium carbonate to the above filtrate to carbonize lithium (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), stir the reaction of carbonizing lithium, and the speed is 200 r / min. After the carbonization of lithium is completed, filter to obtain lithium carbonate solid and the second filtrate.

[0094] Step 4: Wash the lithium carbonate solid in reverse flow for 3 times, and vacuum evaporate and dry at 120°C and normal pressure to obtain 5.88g of lithium carbonate with a purity of 99.92%. Add 45.18g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 23.47g of sodium chloride with a purity of 98.74%.

[0095] The mass of lithium chloride input this time is 12.96g, the lithium equivalent is 2.12g, the generated lithium hydroxide with a purity of 99.99% is 3.51g, the lithium equivalent is 1.02g, the generated lithium carbonate with a purity of 99.82% is 5.58g, the lithium equivalent is 1.05g, and the lithium yield of this group of experiments is Q2=(1.02+1.05) / 2.12×100=97.64%.

[0096] Example 3

[0097] <Example when the ethanol proportion is 55%>

[0098] Step 1: Weigh 6.99 g of solid LiCl and dissolve it in 55 g of ethanol solution. Weigh 6.6 g of solid sodium hydroxide and dissolve it in 45 g of deionized water. The mass ratio of LiCl to sodium hydroxide is 1.06. The mass ratio of ethanol in the composite binary ethanol aqueous solution is 55%. At 25 °C, mix the aqueous solution of sodium hydroxide and the ethanol solution of lithium chloride for alkali precipitation of lithium. The reaction time is 8 min. Stirring is added during the lithium precipitation reaction, and the rotation speed is 200 r / min. After the lithium precipitation is completed, filter to obtain lithium hydroxide solid and filtrate.

[0099] Step 2: Wash the lithium hydroxide solid 5 times with saturated lithium hydroxide solution in a countercurrent manner. Vacuum evaporate and dry it at 180 °C and 0.01 mpa to obtain 1.96 g of lithium hydroxide with a purity of 99.96%. According to the masses of added lithium chloride and sodium hydroxide, it is calculated that 3.95 g of lithium hydroxide is generated in the reaction. The lithium hydroxide yield in this group of experiments is W3 = (1.96×0.9996) / 3.95×100 = 49.6%.

[0100] Step 3: Add 4.4 g of sodium carbonate to the above filtrate for carbonation precipitation of lithium (the molar ratio of the precipitant to lithium hydroxide in the filtrate is 1:2). Stirring is added during the carbonation precipitation reaction of lithium, and the rotation speed is 200 r / min. After the carbonation precipitation of lithium is completed, filter to obtain lithium carbonate solid and a second filtrate.

[0101] Step 4: Wash the lithium carbonate solid 3 times in a countercurrent manner. Vacuum evaporate and dry it at 120 °C and normal pressure to obtain 2.77 g of lithium carbonate with a purity of 99.89%. After the second filtrate is subjected to an acid-base neutralization reaction with 17.49 g of hydrochloric acid (concentration 8%) and then evaporated to crystallization, 11.70 g of sodium chloride with a purity of 97.46% is obtained.

[0102] The mass of lithium chloride input this time is 6.99 g, and the lithium equivalent is 1.145 g. 1.96 g of lithium hydroxide with a purity of 99.96% is generated, and the lithium equivalent is 0.568 g. 2.77 g of lithium carbonate with a purity of 99.89% is generated, and the lithium equivalent is 0.521 g. The lithium recovery rate Q3 in this group of experiments = (0.568 + 0.521) / 1.145×100 = 95.11%.

[0103] Example 4

[0104] <The reaction temperature of step S100 is high temperature 95 °C>

[0105] Step 1: Weigh 6.99g of LiCl solid and dissolve it in 55g of ethanol solution, weigh 6.6g of sodium hydroxide solid and dissolve it in 45g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of ethanol in the alcohol composite solvent is 55%, and the aqueous solution of sodium hydroxide and the ethanol solution of lithium chloride are mixed at 95°C for alkalization and lithium precipitation. The reaction time is 5min, stirring is added to the lithium precipitation reaction, the rotation speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0106] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 2.05 g of lithium hydroxide with a purity of 99.98%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 3.95 g of lithium hydroxide was generated by the reaction, and the lithium hydroxide yield of this group of experiments was W4 = (2.05 × 0.9998) / 3.95 × 100 = 51.9%.

[0107] Compared with the W4 yield of 49.6% in Example 3, the reason for the increase in lithium hydroxide yield is that ethanol is preferentially evaporated at a high temperature of 95° C., which reduces the proportion of ethanol in the mixed solution.

[0108] Step 3: Add 4.21 g of sodium carbonate to the above filtrate to carbonize lithium (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), and stir the carbonization reaction at a speed of 200 r / min. After the carbonization of lithium is completed, filter to obtain lithium carbonate solid and the second filtrate.

[0109] Step 4: Wash the lithium carbonate solid in reverse flow for 3 times, and vacuum evaporate and dry at 120°C and normal pressure to obtain 2.73g of lithium carbonate with a purity of 99.90%. Add 15.63g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 11.52g of sodium chloride with a purity of 97.96%.

[0110] The mass of lithium chloride input this time is 6.99g, the lithium equivalent is 1.145g, and the generated lithium hydroxide with a purity of 99.96% is 2.05g, the lithium equivalent is 0.594g, the generated lithium carbonate with a purity of 99.90% is 2.73g, and the lithium equivalent is 0.513g. The lithium yield of this group of experiments is Q4=(0.594+0.513) / 1.145×100=96.68%.

[0111] Compared with the Q3 yield of 95.08% in Example 3, the reason for the improvement in lithium yield is that ethanol is preferentially evaporated at a high temperature of 95°C, which reduces the proportion of ethanol in the mixed solution and improves the lithium hydroxide yield, while having little effect on lithium carbonate.

[0112] Example 5

[0113] In both Example 5 and Example 4, alcohol compounds account for a large proportion. The difference between Example 5 and Example 4 is that the temperature of Example 5 during the alkalization and lithium precipitation reaction is 50°C, and the others are the same as Example 4. Compared with Example 3, the yields of lithium hydroxide corresponding to Example 5 and Example 4 are both higher, and the overall yield of lithium element is also better. Lithium hydroxide yield W5 = 51.2%, lithium yield Q5 = 96.68%.

[0114] Example 6

[0115] Similar to Example 1, the main difference is that the mass ratio of ethanol in the composite dibasic ethanol aqueous solution is 30%, specifically as follows:

[0116] Step 1: Weigh 14.65g of LiCl solid and dissolve it in 30g of ethanol solution, weigh 13.82g of sodium hydroxide solid and dissolve it in 70g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of ethanol in the alcohol composite solvent is 30%, and the aqueous solution of sodium hydroxide and the ethanol solution of lithium chloride are mixed at 25°C for alkalization and lithium precipitation. The reaction time is 5min, stirring is added to the lithium precipitation reaction, the rotation speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0117] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 3.66 g of lithium hydroxide with a purity of 99.91%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 8.28 g of lithium hydroxide was generated by the reaction, and the lithium hydroxide yield of this group of experiments was W6 = (3.66 × 0.9991) / 8.28 × 100 = 44.16%.

[0118] Step 3: Add 10.22 g of sodium carbonate to the above filtrate for lithium carbonization precipitation (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), stir the lithium carbonization precipitation reaction at a speed of 200 r / min, and filter after the lithium carbonization precipitation is completed to obtain lithium carbonate solid and the second filtrate.

[0119] Step 4: Wash the lithium carbonate solid in reverse flow for 3 times, and vacuum evaporate and dry at 120°C and normal pressure to obtain 6.33g of lithium carbonate with a purity of 99.76%. Add 68.56g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 28.51g of sodium chloride with a purity of 97.22%.

[0120] The mass of lithium chloride input this time is 14.65g, the lithium equivalent is 2.399g, and the generated lithium hydroxide with a purity of 99.91% is 3.66g, the lithium equivalent is 1.060g, and the generated lithium carbonate with a purity of 99.76% is 6.33g, the lithium equivalent is 1.189g. The lithium yield of this group of experiments is Q6=(1.060+1.189) / 2.399×100=93.75%.

[0121] By comparing this embodiment with Example 1, it can be seen that when the ethanol ratio decreases from 47.6% to 30%, the lithium hydroxide yield decreases from 52.9% to 44.17%, and the lithium yield decreases from 95.3% to 93.73%. The lithium hydroxide yield and lithium yield are not as good as those in Example 1.

[0122] Example 7

[0123] Step 1: Weigh 11.82g of LiCl solid and dissolve it in a mixed solvent consisting of 15.2g of ethanol and 23.4g of methanol, weigh 11.15g of sodium hydroxide solid and dissolve it in 61.4g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of organic solvent in the composite solvent consisting of composite ternary ethanol, methanol and aqueous solution is 38.56%, and the aqueous solution of sodium hydroxide and the ethanol / methanol solution of lithium chloride are mixed at 10°C for alkalization and lithium precipitation, the reaction time is 10min, stirring is added to the lithium precipitation reaction, the rotation speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0124] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 3.32 g of lithium hydroxide with a purity of 99.99%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 6.67 g of lithium hydroxide was generated in the reaction, and the lithium hydroxide yield of this group of experiments was W7 = (3.32 × 0.9999) / 6.67 × 100 = 49.77%.

[0125] Step 3: Add 7.42 g of sodium carbonate to the above filtrate for lithium carbonization precipitation (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), add stirring to the lithium carbonization precipitation reaction at a speed of 200 r / min, and filter after the lithium carbonization precipitation is completed to obtain lithium carbonate solid and the second filtrate.

[0126] Step 4: Wash the lithium carbonate solid in reverse flow for 3 times, and vacuum evaporate and dry at 120°C and normal pressure to obtain 4.87g of lithium carbonate with a purity of 99.79%. Add 36.77g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 20.82g of sodium chloride with a purity of 98.57%.

[0127] The mass of lithium chloride input this time is 11.82g, the lithium equivalent is 1.935g, the generated lithium hydroxide with a purity of 99.99% is 3.32g, the lithium equivalent is 0.964g, the generated lithium carbonate with a purity of 99.79% is 4.87g, the lithium equivalent is 0.915g, and the lithium yield of this group of experiments is Q7=(0.964+0.915) / 1.935×100=97.11%.

[0128] Example 8

[0129] Step 1: Weigh 10.93g of LiCl solid and dissolve it in a mixed solvent consisting of 28.68g of ethanol and 12.69g of ethylene glycol, weigh 10.31g of sodium hydroxide solid and dissolve it in 58.63g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of organic solvent in the composite solvent consisting of composite triethanol, ethylene glycol and aqueous solution is 41.37%, and the aqueous solution of sodium hydroxide and the ethanol / methanol solution of lithium chloride are mixed at 35°C for alkalization and lithium precipitation, stirring is added during the lithium precipitation reaction, the speed is 200r / min, and filtering is performed after the lithium precipitation is completed to obtain lithium hydroxide solid and filtrate.

[0130] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 250°C and 0.01 MPa to obtain 2.96 g of lithium hydroxide with a purity of 99.99%. According to the mass calculation of the added lithium chloride and sodium hydroxide, 6.17 g of lithium hydroxide was generated in the reaction, and the lithium hydroxide yield of this group of experiments was W8 = (2.96 × 0.9999) / 6.17 × 100 = 48%.

[0131] Step 3: Add 7.10 g of sodium carbonate to the above filtrate for lithium carbonization precipitation (the molar ratio of the precipitant to the lithium hydroxide in the filtrate is 1:2), add stirring to the lithium carbonization precipitation reaction at a speed of 200 r / min, and filter after the lithium carbonization precipitation is completed to obtain lithium carbonate solid and the second filtrate.

[0132] Step 4: Wash the lithium carbonate solid in countercurrent for 3 times, and vacuum evaporate and dry at 250°C and normal pressure to obtain 4.65g of lithium carbonate with a purity of 99.91%. Add 38.65g of hydrochloric acid (concentration of 8%) to the second filtrate for acid-base neutralization reaction, and evaporate and crystallize to obtain 19.84g of sodium chloride with a purity of 98.50%.

[0133] The mass of lithium chloride input this time is 10.93g, the lithium equivalent is 1.790g, the generated lithium hydroxide with a purity of 99.99% is 2.96g, the lithium equivalent is 0.859g, the generated lithium carbonate with a purity of 99.91% is 4.65g, the lithium equivalent is 0.874g, and the lithium yield of this group of experiments is Q8=(0.859+0.874) / 1.790×100=96.82%.

[0134] Example 9

[0135] <Example when the proportion of glycerol is 35%)>

[0136] Weigh 10g of LiCl solid and dissolve it in 35g of ethanol solution, weigh 12.22g of sodium hydroxide solid and dissolve it in 65g of deionized water, the mass ratio of LiCl to sodium hydroxide is 0.82, the mass ratio of ethanol in the alcohol composite solvent is 35%, and the aqueous solution containing sodium hydroxide and the ethanol solution containing lithium chloride are mixed at 25°C for alkalization and lithium precipitation reaction, the reaction time is 5min, the lithium precipitation reaction is added with stirring, the speed is 200r / min, and the lithium precipitation is completed and filtered to obtain lithium hydroxide solid and filtrate. The lithium hydroxide solid is countercurrent washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried under 180°C and 0.01mpa. According to the mass calculation of the added lithium chloride and sodium hydroxide, the lithium hydroxide yield of this group of experiments is W9=46.23%. Sodium carbonate is then added to the above filtrate for carbonization and lithium precipitation, and the lithium yield of this group of experiments is Q9=96.11%.

[0137] Example 10

[0138] Weigh 12.96g of LiCl solid and dissolve it in 35g of ethanol solution, weigh 12.22g of potassium hydroxide solid and dissolve it in 65g of deionized water, the mass ratio of LiCl to potassium hydroxide is 1.06, the mass ratio of ethanol in the alcohol composite solvent is 35%, and the aqueous solution containing sodium hydroxide and the ethanol solution containing lithium chloride are mixed at 25°C for alkalization and lithium precipitation reaction, the reaction time is 5min, the lithium precipitation reaction is added with stirring, the speed is 200r / min, and the lithium precipitation is completed and filtered to obtain lithium hydroxide solid and filtrate. The lithium hydroxide solid is countercurrent washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried under 180°C and 0.01mpa. According to the mass calculation of the added lithium chloride and sodium hydroxide, the lithium hydroxide yield of this group of experiments is W10=48.26%. Sodium carbonate is then added to the above filtrate for carbonization and lithium precipitation, and the lithium yield of this group of experiments is Q10=96.81%.

[0139] Comparative Example 1

[0140] <Reaction environment contains only water>

[0141] Step 1: Weigh 26.26g of LiCl solid and dissolve it in 50g of deionized water, weigh 24.77g of sodium hydroxide solid and dissolve it in 50g of deionized water, the mass ratio of LiCl to sodium hydroxide is 1.06, the mass ratio of ethanol in the composite dibasic ethanol aqueous solution is 0%, and the aqueous solution of sodium hydroxide and the aqueous solution of lithium chloride are mixed at 25°C for alkalization and lithium precipitation. Stirring is added during the lithium precipitation reaction at a speed of 200r / min. After the lithium precipitation is completed, filtering is performed to obtain lithium hydroxide solid and filtrate.

[0142] Step 2: The lithium hydroxide solid was counter-washed 5 times with a saturated lithium hydroxide solution, and vacuum evaporated and dried at 180°C and 0.01 MPa to obtain 2.43 g of lithium hydroxide with a purity of 1.43 g. According to the mass calculation of the added lithium chloride and sodium hydroxide, 14.83 g of lithium hydroxide was generated in the reaction, and the lithium hydroxide yield of this group of experiments was W11 = 2.43 / 14.83*100 = 16.4%.

[0143] The raw material parameters, reaction condition parameters and test results in the above Examples 1 to 10 and Ratio 1 can all be found in Table 1. The following table is Table 1. "--" in Table 1 means no relevant parameters.

[0144] Table 1

[0145]

[0146] Comparison between Example 1 and Comparative Example 1 shows that the yield of lithium hydroxide prepared in Example 1 is only 16.4% by using only water as the reaction environment of alkali metal hydroxide and lithium chloride. In Example 1, the yield of lithium hydroxide prepared by using alcohol composite solvent as the reaction environment of alkali metal hydroxide and lithium chloride can reach 52.9%, which is about 36.5% higher than that of Comparative Example 1, and the total yield of lithium element in Example 1 is also as high as 95.3%.

[0147] Embodiment 1 to Embodiment 6 and combination Figure 1 and Figure 2 It can be seen that further regulating the proportion of ethanol in the alcohol composite solvent within a suitable range (e.g., 30% to 60%) is more conducive to the preparation of high-yield lithium hydroxide and high-yield lithium element. In particular, further regulating the proportion of ethanol in the alcohol composite solvent within a preferred range (e.g., 35% to 55%) has a better effect on improving the yield of lithium hydroxide and the yield of lithium element.

[0148] From Examples 7 to 10, it can be seen that adjusting the different types of alcohol compounds is within the scope described in the present application. At the same time, adjusting the different types of alkali metal hydroxides and synergistically regulating the ratio of raw materials and the parameters of the alkalization lithium precipitation reaction are also within the scope of the present application, and it is also possible to prepare high-yield lithium hydroxide and high-yield lithium elements.

[0149] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing battery-grade lithium hydroxide, characterized in that: The preparation method comprises the following steps: S100, obtaining a mixed solution of lithium chloride, alkali metal hydroxide and an alcohol composite solvent, performing an alkali lithium precipitation reaction, filtering, and obtaining lithium hydroxide solid and a filtrate; S200, washing the lithium hydroxide solid in countercurrent, drying and crystallizing to obtain battery-grade lithium hydroxide; Wherein, the alcohol composite solvent comprises an alcohol compound and water; based on the total mass of the alcohol composite solvent, the mass percentage of the alcohol compound is n, 30wt%≤n≤60wt%; S300, adding a carbonate-containing precipitant to the filtrate or introducing carbon dioxide to perform a carbonization lithium precipitation reaction, filtering to obtain lithium carbonate solid and a second filtrate, wherein the filtrate contains the alcohol composite solvent; S400, the lithium carbonate solid is washed and dried to obtain finished lithium carbonate, and the second filtrate is neutralized with hydrochloric acid aqueous solution, evaporated and crystallized to obtain chloride; Wherein, in step S100, obtaining a mixed solution of lithium chloride, alkali metal hydroxide and alcohol composite solvent includes: dissolving lithium chloride in water and dissolving alkali in alcohol compound, and then mixing the two; or dissolving lithium chloride in alcohol compound and dissolving alkali in water, and then mixing the two.

2. The preparation method according to claim 1, characterized in that: The preparation method satisfies at least one of the following conditions: (1) In step S200, the solution of the countercurrent washing includes a saturated lithium hydroxide solution, the number of countercurrent washings is 3 to 10 times, the temperature of the drying crystallization is 180° C. to 250° C., and the pressure is 0.01 MPa to 0.1 MPa; (2) In step S300, the precipitant includes sodium carbonate and / or potassium carbonate; (3) In step S300, when carbon dioxide is introduced into the filtrate, the carbonization and lithium precipitation reaction further includes: pyrolyzing the reaction solution at 75°C to 95°C for 2h to 4h, and then filtering.

3. The preparation method according to claim 1, characterized in that: The alcohol compound includes at least one of a low-carbon monohydric alcohol or a low-carbon polyhydric alcohol; The low-carbon monohydric alcohol is selected from any one of C1 to C4 monohydric alcohols; The low-carbon polyol is selected from any one of C1 to C4 polyols.

4. The preparation method according to claim 3, characterized in that: The low-carbon monohydric alcohol includes any one of methanol, ethanol, and isopropanol; The low-carbon polyol includes any one of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, ethylene glycol and propylene glycol, glycerol and trimethylolpropane.

5. The preparation method according to any one of claims 1 to 4, characterized in that: 35wt%≤n≤55wt%.

6. The preparation method according to claim 1, characterized in that: The alcohol composite solvent is a composition of an alcohol compound and water.

7. The preparation method according to claim 5, characterized in that: In step S100, at least one of the following conditions is met: (1) The mass of the alcohol composite solvent is W, the sum of the masses of the lithium chloride and the alkali metal hydroxide is W′, and the following conditions are satisfied: W:W′=1:(0.1-0.3); (2) The mass ratio of the lithium chloride to the alkali metal hydroxide is 0.7 to 1.16; (3) The conditions of the alkalinization lithium precipitation reaction include: reaction temperature of 10°C to 99°C, reaction time of 0.1min to 20min, and reaction speed of 150r / min to 300r / min; (4) The alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide.

8. The preparation method according to claim 7, characterized in that: In step S100, at least one of the following conditions is met: (1) The mass of the alcohol composite solvent is W, the sum of the masses of the lithium chloride and the alkali metal hydroxide is W′, and the following conditions are satisfied: W:W′=1:(0.13-0.26); (2) The mass ratio of the lithium chloride to the alkali metal hydroxide is 1.03 to 1.08; (3) The conditions of the alkaline lithium precipitation reaction include: a reaction temperature of 25°C to 95°C, a reaction time of 2min to 10min, and a rotation speed of 180r / min to 220r / min.

9. The preparation method according to claim 5, characterized in that: When 30%≤n≤M%, the temperature of the alkalization lithium precipitation reaction is 10-35°C; When M%<n≤60%, the temperature of the alkalinization lithium precipitation reaction is 50~95℃; Among them, the value range of M is 47≤M≤48.

10. The preparation method according to claim 9, characterized in that: When 35%≤n≤M%, the temperature of the alkalization lithium precipitation reaction is 10-35°C; when M%<n≤55%, the temperature of the alkalization lithium precipitation reaction is 50-95°C.

11. The preparation method according to claim 9, characterized in that: When the alcohol composite solvent is a composition of an alcohol compound and water, When 30%≤n≤47.6%, the temperature of the alkalinization lithium precipitation reaction is 10-35°C; When 47.6%<n≤60%, the temperature of the alkalization lithium precipitation reaction is 50-95°C.

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