Method for preparing battery-grade lithium hydroxide and high-purity chloride salt and its application

Abstract

The present application discloses a method for preparing battery-grade lithium hydroxide and high-purity chloride salt and its application, comprising the following steps: obtaining a mixture containing lithium chloride, alkali metal hydroxide and a composite solvent, performing an alkalization lithium precipitation reaction, obtaining a product a and a first filtrate, evaporating and crystallizing the first filtrate to obtain a slag, mixing the slag with an alcohol substance, and performing separation treatment to obtain a product b and a second filtrate, evaporating and crystallizing the second filtrate to obtain a product a′, counter-current washing, drying and crystallizing the product a and the product a′ to obtain battery-grade lithium hydroxide, and washing and drying the product b to obtain chloride salt. The present application reacts lithium chloride and a strong base in a composite solvent to generate a lithium hydroxide product and a chloride salt residue, and the chloride salt residue is dissolved and filtered by an organic solvent to separate lithium hydroxide. The comprehensive yield of lithium hydroxide in this process is more than 99%, and the amount of ethanol required per unit of lithium hydroxide can be as low as 46.92g.

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 high-purity chloride salts and applications thereof. Background Art

[0002] Lithium hydroxide is one of the important lithium compounds, which is widely used in the fields of lithium battery industry, lubricant industry and military industry. In the battery industry, lithium hydroxide is an important basic raw material for the preparation of lithium batteries. In the lubricant industry, adding lithium hydroxide to lubricants can significantly improve the performance of lubricants. In the military industry, lithium hydroxide is widely used as a carbon dioxide absorbent to purify breathing gas in spacecraft and submarines.

[0003] The traditional method for preparing lithium hydroxide is the lithium carbonate causticization method, and the reaction equation is as follows:

[0004] Li2CO3+Ca(OH)2=CaCO3↓+2LiOH

[0005] Lithium carbonate and calcium hydroxide are mixed in a ratio of 1:1.08 and heated for half an hour. After the reaction, calcium carbonate enters the filter residue in the form of precipitation. The calcium carbonate is removed by filtration to obtain a lithium hydroxide mother liquor. The mother liquor is evaporated, crystallized, washed, and dried to obtain a lithium hydroxide product. However, the calcium hydroxide in the lithium hydroxide mother liquor is difficult to remove, and the product has the problem of excessive calcium content.

[0006] The prior art discloses a method for preparing lithium hydroxide, wherein an alkali solution and lithium chloride are reacted in an aqueous solution to prepare lithium hydroxide, and when the lithium hydroxide reaches saturated solubility in the aqueous solution, precipitation begins, and the precipitate is filtered, washed, dried, and crystallized to obtain a lithium hydroxide product. However, in order to ensure the purity of the lithium hydroxide product, the process needs to ensure unsaturated precipitation of the byproduct chloride salt while ensuring saturated precipitation of the lithium hydroxide, thus greatly reducing the lithium hydroxide yield. According to calculations, the lithium hydroxide yield of the process is only about 16.4%. Summary of the invention

[0007] In view of this, the present application provides a method for preparing battery-grade lithium hydroxide and high-purity chloride salt and its application, wherein lithium chloride and a strong base are reacted in a polysolvent (complex solvent), the main product (lithium hydroxide) generated by the reaction has a low solubility in the polysolvent, while the by-product (chloride salt) generated has a high solubility in the polysolvent, and the initial reaction can produce a large amount of lithium hydroxide precipitate in the polysolvent, and the remaining lithium hydroxide can be dissolved and separated by a small amount of organic solvent. The present application can achieve a high yield of lithium hydroxide and significantly reduce the use of organic solvents.

[0008] In a first aspect, the present application provides a method for preparing battery-grade lithium hydroxide and high-purity chloride salt, comprising the following steps:

[0009] S100, mixing lithium chloride, alkali metal hydroxide and a composite solvent, performing an alkalization lithium precipitation reaction, filtering, and obtaining a product a and a first filtrate. The composite solvent comprises an alcohol substance and water, the alcohol substance comprises at least one of a low-carbon monohydric alcohol, a low-carbon dihydric alcohol or a low-carbon polyhydric alcohol, the product a comprises lithium hydroxide, and the first filtrate comprises lithium hydroxide and a chloride salt.

[0010] S200, the first filtrate is evaporated and crystallized to obtain a slag material, the slag material is mixed with an alcohol substance, and separated to obtain a product b and a second filtrate, wherein the slag material includes lithium hydroxide and chloride salt, the product b includes chloride salt, and the second filtrate includes lithium hydroxide.

[0011] S300, the second filtrate is evaporated and crystallized to obtain product a', the product a and the product a' are counter-current washed, dried and crystallized to obtain battery-grade lithium hydroxide. The product a' includes lithium hydroxide.

[0012] S400, the product b is washed and dried to obtain high-purity chloride salt;

[0013] There is no particular order for step S300 and step S400. For example, after obtaining product b and the second filtrate, product b can be processed first (i.e., step S400) and then the second filtrate can be processed (i.e., step S300). Alternatively, the above steps can be performed sequentially. Alternatively, product b and the second filtrate can be processed simultaneously. This application does not limit this.

[0014] In step S100, obtaining a mixture containing lithium chloride, alkali metal hydroxide and a composite solvent includes: dissolving lithium chloride in an alcohol substance, dissolving alkali metal hydroxide in water, and then mixing the two, or dissolving lithium chloride in water, dissolving alkali metal hydroxide in an alcohol substance, and then mixing the two to obtain the blended solution. 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.

[0015] In the present application, lithium chloride and a strong base are reacted in a composite solvent (a mixture of an alcohol substance and water), and the solubility of the generated lithium hydroxide in the composite solvent can be reduced to a minimum of 1.88 g / 100 g, see Figure 2 (Taking the composite binary solvent of water and ethanol as an example), compared with the prior art lithium hydroxide solubility of 12.4g / 100g in water, the significant reduction in the solubility of lithium hydroxide in the composite solvent in this application can significantly increase the yield of battery-grade lithium hydroxide. Figure 3 As shown, Figure 3The invention discloses a method for preparing the lithium hydroxide product of the present invention. The method is as follows: the yield of lithium hydroxide in the first process (alkalization and lithium precipitation reaction) of the present invention is as high as 52.9%. The filtrate (first filtrate) produced by filtration is evaporated and crystallized to produce a chloride salt residue (slag material) containing lithium hydroxide. The chloride salt residue containing lithium hydroxide is added to an organic solvent (alcoholic substance) for dissolution (i.e., the second process). Since lithium hydroxide has a high solubility in organic solvents and chloride salt is insoluble in organic solvents, the separation of lithium hydroxide and chloride salt is achieved by filtration after dissolution. The filtered lithium hydroxide filtrate is evaporated, crystallized, washed, and dried to obtain a lithium hydroxide product again, and the recovery of lithium hydroxide in the chloride salt residue is achieved. The comprehensive yield of lithium hydroxide obtained by the present process (the sum of the yields of the first process and the second process) can reach more than 99% and the product has a high purity. In addition, if lithium chloride and a strong base are reacted only in an organic solvent (such as an alcoholic substance), the generated insoluble chloride salt is filtered out, and then the dissolved lithium hydroxide is evaporated and crystallized to obtain a lithium hydroxide product. However, due to the low solubility of lithium hydroxide in an organic solvent, taking ethanol dissolution as an example, the solubility of lithium hydroxide in ethanol is only (1.25-1.33) g / 100g, and the polarity of ethanol is relatively large, and the solubility of other organic solvents relative to lithium hydroxide is lower, resulting in the whole process consuming a large amount of organic solvent. Therefore, the present application, by carrying out the alkalization and precipitation reaction of the first process of lithium chloride and a strong base in a polyvalent solvent and the separation treatment of the second process in an organic solvent, can not only take into account the high comprehensive yield of lithium hydroxide, but also significantly reduce the usage of the organic solvent (including the total amount of the first process and the second process), reducing by about 70%.

[0016] In some embodiments, 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 is 1 to 4) alcohol substances, especially the above-mentioned types of low-carbon monohydric alcohols, low-carbon dihydric alcohols and low-carbon trihydric alcohols, which is more conducive to taking into account both improving the comprehensive yield of lithium hydroxide and reducing the amount of organic solvents. Taking ethanol organic solvent as an example, such as Figure 4 As shown, the horizontal axis is the proportion of ethanol in the composite solvent of the first process (alkalization and lithium precipitation), and the vertical axis is the mass of ethanol required to generate unit mass (g) of lithium hydroxide in the process of this application. The minimum value is about 47g, which is 80g of ethanol required to generate unit mass (g) of lithium hydroxide using pure organic solvent. The amount of organic solvent used is greatly reduced.

[0017] In some embodiments, based on the total mass of the composite solvent, the mass percentage of the alcohol substance is n, 20wt%≤n≤60wt%. Preferably, 20wt%≤n≤50wt%. Regulating the mass percentage of the alcohol substance within the above range is conducive to taking into account the high yield of lithium hydroxide (including the combined yield of the first process and the second process) and significantly reducing the amount of organic solvent used.

[0018] In some embodiments, the composite solvent is a composite solution of an alcohol substance and water, and when the alcohol substance is ethanol, 35wt%≤n≤48wt%. Regulating the mass proportion of ethanol within the above range is beneficial to taking into account the high yield of lithium hydroxide and further reducing the amount of ethanol used in the entire process (the amount of ethanol required per unit of lithium hydroxide can be as low as 46.92g).

[0019] In some embodiments, in step S100, the mass of the composite solvent is W, and the sum of the masses of the lithium chloride and the alkali metal hydroxide is W', satisfying: W:W'=1:(0.1-0.35). Preferably, W:W'=1:(0.15-0.26). The proportion of the composite solvent in the reaction system is appropriate, which is beneficial to improving the yield of lithium hydroxide in the first process and reducing the use of the organic solvent.

[0020] In some embodiments, in step S100, the mass ratio of the lithium chloride to the alkali metal hydroxide is 0.7 to 1.16. Preferably, the mass ratio of the lithium chloride to the 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 comprehensive yield of battery-grade lithium hydroxide.

[0021] In some embodiments, in step S100, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 5°C to 99°C, a reaction time of 2min to 30min, and a reaction speed of 100r / min to 2200r / min. Preferably, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 5°C to 25°C, a reaction time of 2min to 10min, and a reaction speed of 180r / min to 220r / min. The reaction system containing lithium chloride, alkali metal hydroxide and a composite solvent is more conducive to the alkalization lithium precipitation reaction under the above-mentioned reaction conditions, thereby improving the yield of lithium hydroxide in the first process and reducing the amount of organic solvent used in the second process.

[0022] 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 positive progress of the alkalization lithium precipitation reaction, further improving the yield of the product lithium hydroxide in the first process.

[0023] In some embodiments, in step S300, 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.

[0024] In a second aspect, the present application provides battery-grade lithium hydroxide produced by any of the methods of the first aspect.

[0025] In a third aspect, the present application provides the use of battery-grade lithium hydroxide prepared by any method of the first aspect in a ternary power battery.

[0026] The present application reacts lithium chloride and a strong base in a composite solvent, wherein the lithium hydroxide generated by the reaction has a low solubility in the composite solvent and the chloride salt generated has a high solubility in the composite solvent, and the initial reaction can produce a large amount of lithium hydroxide precipitation in the composite solvent, and the remaining lithium hydroxide (present in the solution) can be dissolved and separated by a small amount of organic solvent after evaporation. According to calculations, the comprehensive yield of lithium hydroxide obtained by the process method can reach more than 99% and the product has a high purity. At the same time, the consumption of organic solvents in the entire process is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 A schematic diagram of the process for preparing battery-grade lithium hydroxide and high-purity chloride salt in this application;

[0029] Figure 2 Schematic diagram of the solubility change of lithium hydroxide in the composite solvent in this application;

[0030] Figure 3 This is a schematic diagram of the yield change of lithium hydroxide in a composite solvent in this application;

[0031] Figure 4 This is a schematic diagram of the mass of ethanol required per unit mass of lithium hydroxide in this application. DETAILED DESCRIPTION

[0032] 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.

[0033] Battery grade lithium hydroxide and high purity chloride salt method

[0034] See also Figure 1 , is a schematic diagram of the process flow for preparing battery-grade lithium hydroxide and high-purity chloride salt in this application, comprising the following steps:

[0035] S100, mixing lithium chloride, alkali metal hydroxide and a composite solvent, performing an alkalization lithium precipitation reaction, filtering, and obtaining a product a and a first filtrate, wherein the composite solvent comprises an alcohol substance and water, and the alcohol substance comprises at least one of a low-carbon monohydric alcohol, a low-carbon dihydric alcohol or a low-carbon polyhydric alcohol.

[0036] S200, the first filtrate is evaporated and crystallized to obtain a slag material, the slag material and an alcohol substance are mixed and separated to obtain a product b and a second filtrate.

[0037] S300, the second filtrate is evaporated and crystallized to obtain product a′, the product a and the product a′ are countercurrently washed, dried and crystallized to obtain battery-grade lithium hydroxide.

[0038] S400, the product b is washed and dried to obtain high-purity chloride salt.

[0039] Step S300 and step S400 are performed in no particular order. Also, in step S100, obtaining a mixture containing lithium chloride, alkali metal hydroxide and a composite solvent includes: dissolving lithium chloride in an alcohol substance, dissolving alkali metal hydroxide in water, and then mixing the two, or dissolving lithium chloride in water, dissolving alkali metal hydroxide in an alcohol substance, and then mixing the two to obtain the blended solution. 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.

[0040] In the present application, lithium hydroxide is reacted with lithium chloride and a strong base in a composite solvent, and the solubility of the generated lithium hydroxide in the composite solvent can be reduced to 1.88g / 100g at the lowest. 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 composite solvent in the present application can significantly improve the yield of battery-grade lithium hydroxide. At the same time, the chloride salt residue (slag material) containing lithium hydroxide is added to an alcohol substance for dissolution, and the lithium hydroxide in the slag material is recovered after filtration. The comprehensive yield of lithium hydroxide obtained by this process method can reach more than 99% and the product has a higher purity. At the same time, the use of organic solvents in the whole process can be significantly reduced by this process method, saving costs and being more conducive to industrial production.

[0041] In some embodiments, 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 taking into account the high comprehensive yield of lithium hydroxide and taking into account the reduction of the use of organic solvents in the entire process.

[0042] In some embodiments, based on the total mass of the composite solvent, the mass percentage of the alcohol substance is n, 20wt%≤n≤60wt%. In some embodiments, 20wt%≤n≤55wt%. In some embodiments, 20wt%≤n≤50wt%. In some embodiments, 25wt%≤n≤50wt%. The mass percentage of alcohol substances in the above range is more conducive to taking into account the high comprehensive yield of lithium hydroxide and reducing the amount of organic solvent used. In particular, regulating the mass percentage of alcohol substances in the preferred range (e.g., 20% to 50%) can further reduce the amount of organic solvent used and take into account the high comprehensive yield of lithium hydroxide. At this time, the mass of organic solvent required to be used per unit of lithium hydroxide is less than 55g, and the comprehensive yield of lithium hydroxide reaches more than 99.5%. Exemplarily, based on the total mass of the composite solvent, the mass percentage n% of the alcohol substance is 20wt%, 25wt%, 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.

[0043] In some embodiments, the composite solvent is a composite solution of an alcohol substance and water, and when the alcohol substance is ethanol, 35wt%≤n≤48wt%. The mass percentage of ethanol in the above range can significantly reduce the amount of ethanol used in the entire process and take into account the high comprehensive yield of lithium hydroxide. At this time, the mass of the organic solvent required for unit lithium hydroxide is less than 50g, for example, it can be 46g to 48g; the comprehensive yield of lithium hydroxide reaches more than 99.8%. Exemplarily, the mass percentage of ethanol is 35wt%, 38wt%, 40wt%, 45wt%, 47.6wt%, 48wt% or a value within the range composed of any two of these values.

[0044] In some embodiments, in step S100, the mass of the composite solvent is W, and the sum of the masses of the lithium chloride and the alkali metal hydroxide is W', satisfying: W:W'=1:(0.1-0.35). In some embodiments, W:W'=1:(0.1-0.30). In some embodiments, W:W'=1:(0.13-0.28). In some embodiments, W:W'=1:(0.15-0.26). The proportion of the composite solvent in the reaction system is appropriate, which is beneficial to improve the yield of lithium hydroxide in the first process and take into account the reduction of the amount of organic solvent used. 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, 1:0.30, 1:0.32, 1:0.35 or a value within the range composed of any two of these values.

[0045] In some embodiments, in step S100, the mass ratio of the lithium chloride to the alkali metal hydroxide is 0.7 to 1.16. In some embodiments, the mass ratio of the lithium chloride to the alkali metal hydroxide is 1.03 to 1.08. The mass ratio of lithium chloride to alkali metal hydroxide is appropriate, which is conducive to the forward reaction and further improves the comprehensive yield of battery-grade 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.

[0046] In some embodiments, in step S100, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 5°C to 99°C, a reaction time of 2min to 30min, and a reaction speed of 100r / min to 2200r / min. Preferably, the conditions of the alkalization lithium precipitation reaction include: a reaction temperature of 5°C to 25°C, a reaction time of 2min to 10min, and a reaction speed of 180r / min to 220r / min. Under the above reaction conditions, it is more conducive to the alkalization lithium precipitation reaction, improves the yield of lithium hydroxide in the first process, and thus reduces the amount of organic solvent used in the second process. Exemplarily, the reaction temperature is 5°C, 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 2 min, 5 min, 8 min, 10 min, 15 min, 18 min, 20 min, 25 min, 30 min or a value in the range consisting of any two of these values. Exemplarily, the reaction speed is 100 r / min, 150 r / min, 160 r / min, 180 r / min, 200 r / min, 210 r / min, 220 r / min, 260 r / min, 300 r / min, 500 r / min, 800 r / min, 1000 r / min, 1500 r / min, 2000 r / min, 2200 r / min or a value in the range consisting of any two of these values.

[0047] 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 in the first process.

[0048] In some embodiments, in step S300, 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. In this way, the obtained battery-grade lithium hydroxide can be sold directly as a product. 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 within 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 within 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 within the range of any two of these values.

[0049] The following are possible implementations

[0050] The main purpose of the present invention is to provide a method for preparing lithium hydroxide with high yield, aiming to solve the problems of low yield and low purity of lithium hydroxide in the prior art.

[0051] To achieve the above object, the present invention provides a method for preparing lithium hydroxide with a high yield, which comprises the following steps:

[0052] S1, adding a strong base and lithium chloride to a composite solvent to perform an alkalization lithium precipitation reaction, filtering to obtain a filtrate and solid lithium hydroxide after the lithium precipitation reaction is completed, and the solid lithium hydroxide is subjected to a countercurrent washing, drying and crystallization process to obtain a portion of high-purity lithium hydroxide (product a).

[0053] S2, evaporating and crystallizing the filtrate (first filtrate) obtained in S1 to obtain chloride salt / lithium hydroxide (slag), and returning the composite solvent to the alkalization lithium precipitation step for recycling.

[0054] S3, adding the chloride salt / lithium hydroxide obtained in S2 to an organic solvent for organic separation, and then filtering to obtain a filtrate (second filtrate) and a chloride salt, and countercurrent washing, drying and crystallization of the chloride salt to obtain a by-product high-purity chloride salt.

[0055] S4, evaporating and crystallizing the filtrate obtained in S3, counter-current washing, drying and crystallizing to obtain a part of the product lithium hydroxide (product a′), and returning the organic solvent produced by evaporation and crystallization to the organic separation step for recycling.

[0056] Furthermore, in the above step S1, the composite solvent comprises a composite solvent composed of an organic solvent and water, wherein the organic solvent is mainly monohydric alcohol, such as methanol, ethanol, etc., and the organic solvent may also be polyhydric alcohol, such as ethylene glycol, etc.

[0057] Furthermore, the content of the organic solvent in the composite solvent in the above step S1 ranges from 5% to 65%, preferably from 30% to 50%, the yield of lithium hydroxide in the alkalization lithium precipitation stage is above 40%, and the amount of organic solvent is saved by more than 10%.

[0058] Furthermore, in the above step S1, the optimal mass ratio of lithium chloride to alkali is 0.7 to 1.16, and the preferred optimal mass ratio is 1.03 to 1.08.

[0059] Furthermore, in the above step S1, the reaction temperature range is 5°C to 99°C, and the reaction time range is 0.1min to 180min. Such process parameters can make the alkalization lithium precipitation reaction more thorough, improve the overall yield of lithium hydroxide and reduce the amount of subsequent organic solvents.

[0060] Furthermore, the alkalization lithium precipitation process in the above step S1 can be stirred synchronously, and the stirring speed is 50r / min to 2000r / min. This process parameter can make the alkalization lithium precipitation reaction more thorough, improve the overall yield of lithium hydroxide and reduce the amount of subsequent organic solvents.

[0061] Furthermore, the strong base in the above step S1 can be sodium hydroxide or potassium hydroxide.

[0062] Furthermore, the solid lithium hydroxide obtained in the above step S1 is countercurrently washed 1 to 10 times, and a saturated lithium hydroxide solution can be used for washing.

[0063] Furthermore, in the above step S2, the temperature range of the evaporation crystallization 1 is 120° C. to 250° C., and the pressure range is 0 MPa to 0.1 MPa.

[0064] Furthermore, in the above step S3, the organic solvent is mainly monohydric alcohol, such as methanol, ethanol, etc., and the organic solvent may also be a polyhydric alcohol such as ethylene glycol. It may be a single organic solvent or a mixture of multiple organic solvents.

[0065] Furthermore, the organic separation process in the above step S3 can be stirred synchronously, and the stirring speed is 50-2000r / min.

[0066] Furthermore, the number of countercurrent washing in the above step S3 is 1 to 10 times.

[0067] Furthermore, in the above step S4, the temperature range of the evaporation crystallization 2 is 120° C. to 250° C., and the pressure range is 0 MPa to 0.1 MPa.

[0068] Furthermore, the number of countercurrent washing in the above step S4 is 1 to 10 times, and a saturated lithium hydroxide solution can be used for washing.

[0069] The present application involves reacting lithium chloride and a strong base in a polysolvent to generate a lithium hydroxide product and a chloride salt residue containing lithium hydroxide. The lithium chloride salt residue containing lithium hydroxide is dissolved and filtered through an organic solvent to separate the lithium hydroxide, thereby recovering the lithium hydroxide in the residue. The comprehensive yield of lithium hydroxide in this process reaches 99.87%.

[0070] Of more direct concern is that the method provided by this process greatly improves the comprehensive yield of lithium hydroxide through the alkalinization lithium precipitation reaction in the first process and the organic solvent separation in the second process, while at the same time can greatly reduce the use of organic solvents (including alcohol solvents in the first process and the second process).

[0071] Process flow chart Figure 1 shown.

[0072] 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.

[0073] Example 1

[0074] <The proportion of ethanol in the composite solvent is 47.6wt%>

[0075] 85.6g of sodium hydroxide was dissolved in 524g of aqueous solution, 90.74g of lithium chloride was dissolved in 476g of ethanol solution, and then the sodium hydroxide aqueous solution was slowly added to the lithium chloride ethanol solution, and the reaction was carried out at 25°C for 20min. The reaction process was simultaneously stirred at 200r / min to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was performed to obtain lithium hydroxide solid and filtrate by filtration, and the lithium hydroxide solid was washed 3 times in reverse flow to obtain 27.10g of lithium hydroxide with a purity of 99.93%. The filtrate was evaporated and crystallized at a temperature of 250°C and a pressure of 0.1MPa to obtain a chloride salt / lithium hydroxide mixture, and the mixture was added to 1930g of ethanol for organic separation, and then a filtrate and sodium chloride solid were obtained by filtration, and the sodium chloride solid was washed 3 times in reverse flow to obtain 124.6g of sodium chloride with a purity of 99.85%. The filtrate was evaporated and crystallized at 180°C to obtain solid lithium hydroxide. The solid lithium hydroxide was countercurrent washed three times and then dried to obtain 24.10 g of lithium hydroxide with a purity of 99.98%.

[0076] Initially, 90.74 g of lithium chloride is added, which is equivalent to 51.28 g of lithium hydroxide equivalent. The lithium hydroxide yield of this process is Q1 = (27.10 × 99.93% + 24.10 × 99.98%) / 51.28 × 100% = 99.80%. In this example, the mass of organic solvent required to generate unit lithium hydroxide is M1 = (476 + 1930) / 51.28 = 46.92 g.

[0077] Example 2

[0078] <The proportion of ethanol in the composite solvent is 35wt%>

[0079] 122g of sodium hydroxide was dissolved in 650g of aqueous solution, 129.5g of lithium chloride was dissolved in 350g of ethanol solution, and then the sodium hydroxide aqueous solution was slowly added to the lithium chloride ethanol solution, and the reaction was carried out at 5°C for 25min. During the reaction, 200r / min stirring was applied simultaneously to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was carried out to obtain lithium hydroxide solid and filtrate by filtration, and the lithium hydroxide solid was countercurrently washed 3 times to obtain 34.97g of lithium hydroxide with a purity of 99.91%. The filtrate was evaporated and crystallized at a temperature of 250°C to obtain a chloride salt / lithium hydroxide mixture, and the mixture was added to a composite organic solution composed of 1550g of methanol and 1550g of ethanol for organic separation, and then the filtrate and sodium chloride solid were obtained by filtration, and the sodium chloride solid was countercurrently washed 3 times to obtain 178.1g of sodium chloride with a purity of 99.82%. The filtrate was evaporated and crystallized at 180°C and 0.1 MPa to obtain solid lithium hydroxide. The solid lithium hydroxide was countercurrent washed three times and then dried to obtain 38.1 g of lithium hydroxide with a purity of 99.99%.

[0080] Initially, 129.5 g of lithium chloride is added, which is equivalent to 73.17 g of lithium hydroxide equivalent. The lithium hydroxide yield of this process is Q2 = (34.97 × 99.91% + 38.1 × 99.99%) / 73.17 × 100% = 99.82%. In this example, the mass of organic solvent required to generate unit lithium hydroxide is M2 = (350 + 1550 + 1550) / 73.17 = 47.15 g.

[0081] Example 3

[0082] <The proportion of ethanol in the composite solvent is 50wt%>

[0083] 69g of sodium hydroxide was dissolved in 500g of aqueous solution, 73.15g of lithium chloride was dissolved in 500g of ethanol solution, and then the sodium hydroxide aqueous solution was slowly added to the lithium chloride ethanol solution, and the reaction was carried out at 35°C for 12min. The reaction process was simultaneously stirred at 200r / min to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was carried out to obtain lithium hydroxide solid and filtrate by filtration, and the lithium hydroxide solid was washed 3 times in reverse flow to obtain 21.38g of lithium hydroxide with a purity of 99.96%. The filtrate was evaporated and crystallized at a temperature of 250°C to obtain a chloride salt / lithium hydroxide mixture, and the mixture was added to 1590g of ethanol organic solution for organic separation, and then the filtrate and sodium chloride solid were obtained by filtration, and the sodium chloride solid was washed 3 times in reverse flow to obtain 100.3g of sodium chloride with a purity of 99.85%. The filtrate was evaporated and crystallized at 180°C and 0.1 MPa to obtain solid lithium hydroxide. The solid lithium hydroxide was countercurrent washed three times and then dried to obtain 19.88 g of lithium hydroxide with a purity of 99.97%.

[0084] Initially, 73.15 g of lithium chloride is added, which is equivalent to 41.31 g of lithium hydroxide. The lithium hydroxide yield of this process is Q3 = (21.38 × 99.96% + 19.88 × 99.97%) / 41.31 × 100% = 99.84%. In this example, the mass of ethanol required to generate unit lithium hydroxide is M3 = (500 + 1590) / 41.31 = 50.60 g.

[0085] Example 4

[0086] <The proportion of ethanol in the composite solvent is 20wt%>

[0087] 167.3g sodium hydroxide was dissolved in 200g ethanol solution, 177.4g lithium chloride was dissolved in 800g aqueous solution, and then the sodium hydroxide aqueous solution was slowly added to the lithium chloride ethanol solution, and the reaction was carried out at 15°C for 22min, and 200r / min stirring was applied synchronously during the reaction process to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was carried out to obtain lithium hydroxide solid and filtrate by filtration, and the lithium hydroxide solid was washed 3 times in reverse flow to obtain 36.70g lithium hydroxide with a purity of 99.89%. The filtrate was evaporated and crystallized at a temperature of 250°C to obtain a chloride salt / lithium hydroxide mixture, and the mixture was added to 5100g ethanol organic solution for organic separation, and then the filtrate and sodium chloride solid were obtained by filtration, and the sodium chloride solid was washed 3 times in reverse flow to obtain 244g sodium chloride with a purity of 99.73%. The filtrate was evaporated and crystallized at 180°C and 0.1 MPa to obtain solid lithium hydroxide. The solid lithium hydroxide was countercurrent washed three times and then dried to obtain 63.16 g of lithium hydroxide with a purity of 99.85%.

[0088] Initially, 177.4 g of lithium chloride is added, which is equivalent to 100.16 g of lithium hydroxide equivalent. The lithium hydroxide yield of this process is Q4 = (36.70 × 99.89% + 63.16 × 99.85%) / 100.16 × 100% = 99.57%. In this example, the mass of ethanol required to generate unit lithium hydroxide is M4 = (200 + 5100) / 100.16 = 52.92 g.

[0089] Example 5

[0090] <The proportion of ethanol in the composite solvent is 60wt%>

[0091] 51.32g of sodium hydroxide was dissolved in 300g of aqueous solution, 54.40g of lithium chloride was dissolved in 600g of ethanol solution, and then the sodium hydroxide aqueous solution was slowly added to the lithium chloride ethanol solution, and the reaction was carried out at 50°C for 10min. The reaction process was simultaneously stirred at 200r / min to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was carried out to obtain lithium hydroxide solid and filtrate by filtration, and the lithium hydroxide solid was washed 3 times in reverse flow to obtain 11.97g of lithium hydroxide with a purity of 99.78%. The filtrate was evaporated and crystallized at a temperature of 250°C to obtain a chloride salt / lithium hydroxide mixture, and the mixture was added to a 1500g ethanol organic solution for organic separation, and then a filtrate and sodium chloride solid were obtained by filtration, and the sodium chloride solid was washed 3 times in reverse flow to obtain 74.5g of sodium chloride with a purity of 99.79%. The filtrate was evaporated and crystallized at 180°C and 0.1 MPa to obtain solid lithium hydroxide. The solid lithium hydroxide was countercurrent washed three times and then dried to obtain 18.62 g of lithium hydroxide with a purity of 99.82%.

[0092] Initially, 54.40 g of lithium chloride is added, which is equivalent to 30.72 g of lithium hydroxide equivalent. The lithium hydroxide yield of this process is Q5 = (11.97 × 99.78% + 18.62 × 99.82%) / 30.72 × 100% = 99.38%. In this example, the mass of ethanol required to generate unit lithium hydroxide is M5 = (600 + 1500) / 30.72 = 68.36 g.

[0093] Comparative Example 1

[0094] <Solvent with only ethanol, Example 1 for comparison>

[0095] 85.6g of sodium hydroxide and 90.74g of lithium chloride were dissolved in 4100g of ethanol solution, and the reaction was carried out at 25°C for 20min. During the reaction, 200r / min stirring was applied simultaneously to carry out alkalization and lithium precipitation reaction. After the reaction was completed, a filtering operation was carried out to obtain lithium hydroxide solid and filtrate. The sodium chloride solid was countercurrently washed 3 times to obtain 124.4g of sodium chloride with a purity of 99.86%. The filtrate was evaporated and crystallized at 180°C to obtain lithium hydroxide solid. The lithium hydroxide solid was countercurrently washed 3 times and then dried to obtain 51.2g of lithium hydroxide with a purity of 99.96%.

[0096] Initially, 90.74 g of lithium chloride is added, which is equivalent to 51.28 g of lithium hydroxide equivalent. The lithium hydroxide yield of this process Q6 = (51.2 × 99.98%) / 51.28 × 100% = 99.82%. In this example, the mass of organic solvent required to generate unit lithium hydroxide is M1 = 4100 / 51.28 = 80 g. From the comparison between this comparative example and Example 1, it can be seen that the mass of organic solvent required to generate unit lithium hydroxide increases by 70.5%.

[0097] The first process in Table 1 refers to the process of alkalization and lithium precipitation reaction, and the second process refers to the process of separating and treating the lithium hydroxide in the slag. The following table is Table 1. The ethanol and methanol in Table 1 both refer to anhydrous ethanol and anhydrous methanol.

[0098] Table 1

[0099]

[0100] Compared with Example 1, Comparative Example 1 uses only ethanol as the reaction environment for alkali metal hydroxide and lithium chloride. Although the yield of lithium hydroxide prepared in Comparative Example 1 can reach 99.82%, the entire process requires the consumption of a large amount of ethanol. In Example 1, lithium chloride and a strong base are reacted in a composite solvent of ethanol and water, and a large amount of lithium hydroxide precipitation can be produced in the composite solvent in the initial reaction, and the remaining lithium hydroxide can be obtained by dissolving and separating with a small amount of organic solvent. Compared with Example 1 and Comparative Example 1, the mass of ethanol required to generate unit lithium hydroxide in Example 1 is reduced by 70%, and the comprehensive yield of lithium hydroxide in Example 1 is also high.

[0101] Embodiment 1 to Embodiment 5 and combination Figure 3 and Figure 4 It can be seen that regulating the mass proportion of ethanol in the composite solvent of ethanol and water within a suitable range (e.g., 20% to 60%) is conducive to taking into account both the high comprehensive yield of lithium hydroxide and reducing the amount of ethanol used in the entire process. In particular, further regulating the mass proportion of ethanol in the composite solvent of ethanol and water within a preferred range (e.g., 35% to 48%) is conducive to further improving the comprehensive yield of lithium hydroxide and reducing the amount of ethanol used.

[0102] 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 and high-purity chloride salt, characterized in that: The method comprises the following steps: S100, obtaining a mixture containing lithium chloride, alkali metal hydroxide and a composite solvent, performing an alkalization lithium precipitation reaction, filtering, and obtaining a product a and a first filtrate; Wherein, the composite solvent comprises alcohol substances and water; S200, the first filtrate is evaporated and crystallized to obtain a slag material, the slag material is mixed with an alcohol substance, and separated to obtain a product b and a second filtrate, wherein the second filtrate includes lithium hydroxide; S300, the second filtrate is evaporated and crystallized to obtain product a′, and the product a and the product a′ are countercurrently washed, dried and crystallized to obtain battery-grade lithium hydroxide; S400, the product b is washed and dried to obtain a high-purity chloride salt; The alcohol substance includes at least one of a low-carbon monohydric alcohol or a low-carbon polyhydric alcohol; Among them, step S300 and step S400 are performed in no particular order; 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; Based on the total mass of the composite solvent, the mass percentage of the alcohol substance is n, 20wt%≤n≤60wt%.

2. The method according to claim 1, 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, and trimethylolpropane.

3. The method according to claim 1 or 2, characterized in that: 20wt%≤n≤50wt%.

4. The method according to claim 3, characterized in that: The composite solvent is a composite solution of alcohol and water; When the alcohol substance is ethanol, 35wt%≤n≤48wt%.

5. The method according to claim 1 or 2, characterized in that: In step S100, at least one of the following conditions is met: (1) The mass of the composite solvent is W, the sum of the masses of the lithium chloride and the alkali metal hydroxide is W′, and the relationship is: W:W′=1:(0.1-0.35); (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 5°C to 99°C, reaction time of 2min to 30min, and reaction speed of 100r / min to 2200r / min; (4) The alkali metal hydroxide includes sodium hydroxide and / or potassium hydroxide.

6. The method according to claim 5, characterized in that At least one of the following conditions is met: (1) Satisfy: W: W′=1:(0.15~0.26); (2) The mass ratio of the lithium chloride to the alkali metal hydroxide is 1.03 to 1.08; (3) The conditions of the alkalinization lithium precipitation reaction include: the reaction temperature is 5°C to 50°C, the reaction time is 5min~30min, reaction speed is 180r / min~220r / min.

7. The method according to claim 1, characterized in that The obtained product contains lithium chloride, The mixture of alkali metal hydroxide and complex solvent comprises: Dissolving lithium chloride in an alcohol compound and dissolving an alkali metal hydroxide in water, and then mixing the two to obtain the mixture; or, The mixture is obtained by dissolving lithium chloride in water and dissolving an alkali metal hydroxide in an alcohol compound, and then mixing the two.

8. The method according to claim 1, characterized in that: In step S300, the solution of the countercurrent washing includes a saturated lithium hydroxide solution, the number of countercurrent washing 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.

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