A method for preparing battery-grade lithium compounds

Abstract

This invention discloses a method for preparing battery-grade lithium compounds, belonging to the technical field of lithium compound preparation methods. The method includes the following steps: S1, acidifying a lithium-containing raw material with sulfuric acid or calcining it with sulfate, followed by water leaching to obtain a leaching slurry; the lithium-containing raw material is lithium mineral or waste lithium battery material; S2, adding calcium oxide or calcium hydroxide to the leaching slurry, reacting fully, and then filtering to obtain filtrate A and filter residue A; S3, adding a calcium ion-removing substance to filtrate A, reacting fully, and then filtering to obtain filtrate B and filter residue B; S4, fully contacting filtrate B with an extractant for extraction, and then separating to obtain a loaded organic phase and raffinate; S5, back-extracting the loaded organic phase to obtain a lithium solution and a blank organic phase; S6, further processing the lithium solution to obtain battery-grade lithium compounds. This invention essentially does not introduce sodium ions and has advantages such as low energy consumption, simplified process, high product quality, low production cost, high lithium yield, and convenient handling of by-products.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium compound preparation methods, and relates to a method for preparing battery-grade lithium compounds. Background Technology

[0002] With the widespread application of lithium batteries in electronic products (mobile phones, laptops, cameras, etc.), electric vehicles, and energy storage systems, battery-grade lithium compounds are receiving increasing attention. Battery-grade lithium compounds mainly include lithium carbonate, lithium hydroxide, and lithium chloride, with lithium carbonate being the most widely used, accounting for more than 60% of the total battery-grade lithium compounds.

[0003] Lithium minerals and spent lithium batteries are important lithium-containing raw materials. The current common process involves acidifying these raw materials with sulfuric acid or roasting them with sulfates, followed by water leaching to obtain a leachate with lithium sulfate as the main component (lithium ion concentration around 5-13 g / L). Subsequent processes then yield the lithium product. For example, CN109371227A discloses a sulfuric acid process for lithium extraction from spodumene magnetic materials. In this process, a saturated sodium hydroxide solution is added to the lithium sulfate solution obtained from sulfuric acid acidification and roasting to adjust the pH. After precipitation and filtration, a pure lithium hydroxide solution is obtained. The pure lithium hydroxide solution is then evaporated and concentrated to a 20% concentration, followed by the addition of a saturated sodium carbonate solution to precipitate lithium carbonate. After filtration and washing, the lithium carbonate precipitate is vacuum dried to obtain the lithium carbonate product.

[0004] CN102311110A discloses a complete cyclic preparation method for producing lithium iron phosphate using lithium ore as the lithium source. The method involves calcining, acidifying, leaching, and purifying the lithium ore to obtain a primary lithium solution. This primary lithium solution is then subjected to conversion freezing, filtration, washing, and evaporation concentration to obtain a lithium solution for the synthesis reaction. This lithium solution is then subjected to a liquid-phase synthesis reaction with a ferrous salt solution and a phosphorus source solution, followed by calcination to obtain carbon-coated lithium iron phosphate. "Conversion freezing" refers to the addition of sodium salt to the primary lithium solution. The Li₂SO₄ in the primary lithium solution reacts with the sodium salt to produce another lithium salt and Na₂SO₄. The solution is then cooled to allow the generated sodium sulfate to crystallize out and be removed through solid-liquid separation.

[0005] CN115537551A discloses a method for preferentially extracting lithium and manganese from waste lithium battery cathode materials. First, sulfation roasting is used to convert all lithium and manganese into lithium sulfate and manganese sulfate, respectively. After roasting, the lithium and manganese are leached into a solution using water leaching. At this point, a small amount of nickel sulfate and cobalt sulfate are present in the solution. A certain amount of sodium sulfate is added to the solution to remove nickel and cobalt ions. After precipitating manganese ions in the solution using calcium hydroxide or calcium oxide, sodium carbonate is added to the solution to synthesize lithium carbonate. The separation of manganese hydroxide and calcium sulfate is achieved through reducing acid leaching. The manganese sulfate is then concentrated and crystallized to form manganese sulfate.

[0006] It can be seen that although the specific technical solutions have their own characteristics, existing technologies generally require the addition of sodium hydroxide and / or sodium salts (mainly sodium carbonate) after obtaining a leachate with lithium sulfate as the main component, introducing a large amount of sodium ions into the reaction system. This leads to at least three adverse consequences: Firstly, it generates a large amount of low-value sodium sulfate byproducts that are difficult to dispose of (China's annual demand for sodium sulfate is only about 15 million tons. The sodium sulfate byproducts of China's lithium salt industry are already close to 1 million tons, and the sodium sulfate byproducts of China's lithium battery industry are already close to 2 million tons, and both are still increasing rapidly), posing an environmental burden; secondly, in order to separate sodium sulfate, high-energy-consuming methods such as evaporation concentration or freeze crystallization are required; and thirdly, the byproduct sodium sulfate carries lithium, resulting in lithium loss.

[0007] In addition, many existing technologies produce industrial-grade lithium compounds. Battery-grade lithium compounds, compared to industrial-grade lithium compounds, have higher requirements for the content of impurities such as sodium, potassium, calcium, and magnesium. The large amount of sodium ions introduced by existing technologies requires additional impurity removal methods to ensure sufficient removal, which further increases production costs. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing battery-grade lithium compounds. After reacting lithium minerals or waste lithium battery materials with sulfuric acid or roasting sulfates, and then leaching with water to obtain a leaching slurry with lithium sulfate as the main component, calcium oxide or calcium hydroxide is added to provide hydroxide ions. Lithium is enriched and separated from other monovalent metal ions through extraction. After obtaining the lithium extract, appropriate back-extraction and subsequent processes are employed based on the type of the final lithium compound. The entire process essentially does not introduce sodium ions, thus avoiding the generation of low-value sodium sulfate byproducts, the high-energy-consuming operation of separating sodium sulfate, and lithium loss due to lithium entrainment in the sodium sulfate byproduct. The raffinate can be directly recycled for use in the leaching slurry, reducing... Water consumption is reduced; lithium enrichment is achieved through extraction and back-extraction, avoiding the energy-intensive lithium sulfate concentration process; the main raw materials required are extractant (which is recyclable with minimal loss) and inexpensive calcium oxide or calcium hydroxide, carbon dioxide (or even industrial waste gas), etc. Inexpensive calcium oxide or calcium hydroxide and carbon dioxide replace expensive sodium carbonate in lithium carbonate production, and inexpensive calcium oxide or calcium hydroxide replaces expensive sodium hydroxide in lithium hydroxide production. The main byproduct is calcium sulfate, which has a large-scale application (China's annual demand for calcium sulfate is approximately 150 million tons). Compared with existing technologies, this invention has advantages such as low energy consumption, simplified process, low production cost, high product quality, high lithium yield, and convenient byproduct handling. The objective of this invention is achieved through the following specific technical solutions.

[0009] A method for preparing battery-grade lithium compounds includes the following steps:

[0010] S1 involves acidifying the lithium-containing raw material with sulfuric acid or roasting it with sulfate, followed by water leaching to obtain a leaching slurry; the lithium-containing raw material is lithium mineral or waste lithium battery material. The main active component of the leaching slurry is lithium sulfate.

[0011] S2. Calcium oxide or calcium hydroxide is added to the leachate slurry. After sufficient reaction, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly neutralizes excess acid in the leachate slurry with calcium oxide or calcium hydroxide, converts lithium sulfate to lithium hydroxide, introduces hydroxide ions into the system to provide the driving force for extraction, and removes ferric ions, ferrous ions, and most magnesium ions. The main component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching; the main components of filter residue A are lithium mineral slag or waste lithium battery material slag and / or calcium sulfate, and may also contain excess calcium oxide or calcium hydroxide.

[0012] S3. Add a calcium ion remover to filtrate A, allow it to react completely, and then filter to obtain filtrate B and residue B. This step removes the calcium ions introduced by the addition of calcium oxide or calcium hydroxide, as well as the calcium ions from calcium sulfate that are slightly soluble in water, forming an insoluble calcium precipitate.

[0013] S4 involves fully contacting filtrate B with the extractant for extraction, followed by separation to obtain the loaded organic phase and raffinate.

[0014] S5 involves back-extraction of the supported organic phase to obtain a lithium solution and a blank organic phase. Through the extraction and back-extraction process, lithium ions are separated from monovalent metal ions (sodium, potassium), while lithium ions are also enriched.

[0015] S6 further processes the lithium solution to obtain battery-grade lithium compounds.

[0016] Furthermore, by controlling the amount of calcium oxide or calcium hydroxide added, the pH of filtrate A can be adjusted to 12.0-14.0. Within this pH range, most of the lithium sulfate can be converted into lithium hydroxide, thus avoiding the use of sodium hydroxide, which is more expensive than calcium oxide or calcium hydroxide.

[0017] In some specific technical solutions, step S2 is broken down into two steps:

[0018] S2-1 Add an appropriate amount of calcium oxide or calcium hydroxide to the leaching slurry to neutralize the excess acid in the leaching slurry. After the neutralization reaction is completed, filter to obtain filtrate A' and filter residue A'.

[0019] S2-2 Add calcium oxide or calcium hydroxide to filtrate A', and after the reaction is complete, filter to obtain filtrate A and filter residue A.

[0020] Furthermore, in step S2-1, the amount of calcium oxide or calcium hydroxide added is controlled so that the pH value of the filtrate A' is 4.0~11.9, preferably 6.5~7.5. Within the above pH range, excess acid in the leaching slurry can be neutralized, and excessive calcium sulfate slag can be avoided during the neutralization process, thus separating lithium mineral slag or waste lithium battery material slag from calcium sulfate slag as much as possible.

[0021] Furthermore, in step S2-2, the amount of calcium oxide or calcium hydroxide added is controlled so that the pH value of filtrate A is 12.0~14.0.

[0022] Furthermore, in order to fully recover the filter residue A' and the small amount of lithium entrained in the filter residue A, the filter residue A' is added to water and stirred into a slurry. The slurry is filtered to obtain residue and washing liquid. The residue (mainly lithium mineral slag or waste lithium battery material slag) is discharged. The residue after thorough washing is almost free of lithium. The washing liquid is used to wash the filter residue A again. The washed filter residue A (mainly calcium sulfate slag) is discharged. The washing liquid is returned to step S1 for water immersion.

[0023] By breaking down step S2 into two steps, lithium mineral slag or waste lithium battery material slag is separated from calcium sulfate slag as much as possible. In addition, the pH value of the filtrate A' after the neutralization reaction is low, the pH value of the washing liquid after washing the filter residue A' is low, and correspondingly, the pH value of the discharged residue is also low. Since the higher the pH value of the residue, the more extractant is carried away, the less extractant is carried away by the discharged residue after the raffinate is circulated and leached.

[0024] Furthermore, the calcium ion-removing substance mentioned in step S3 is selected from one or more of carbonates, aqueous solutions of carbonates, oxalates, aqueous solutions of oxalates, phosphates, and aqueous solutions of phosphates.

[0025] Since calcium sulfate is slightly soluble in water, by adding substances that remove calcium ions, the water-soluble calcium sulfate can be converted into water-insoluble calcium carbonate, calcium oxalate, or calcium phosphate (the solubility product of calcium sulfate is 9.1 × 10⁻⁶). -6 The solubility product of calcium carbonate is 3.36 × 10⁻⁶. -9 The solubility product of calcium oxalate is 4 × 10⁻⁶. -9 The solubility product of calcium phosphate is 2.0 × 10⁻⁶. -29 ), removing most of the calcium ions.

[0026] Furthermore, in order to fully recover the small amount of lithium entrained in filter residue B and to utilize the calcium precipitate in filter residue B to neutralize sulfuric acid, the filter residue B obtained in step S3 is returned to step S1 for leaching.

[0027] Furthermore, the extractant in step S4 is a composite extractant, comprising a neutral extractant and a chelating extractant, and the extraction system also includes a diluent; the neutral extractant comprises one or a combination of several of the following: tributyl phosphate (TBP), dimethylheptyl methyl phosphate (P350), trioctylphosphine oxide (TOPO), trioctyl / hexylphosphine oxide (Cyanex923), and N,N-di-(1-methylheptyl)acetamide (N503); the chelating extractant comprises one or a combination of several of the following: 2-hydroxy-5-nonylacetophenone oxime (LIX84), dodecylphenyl-methyl-β-dione (LIX54), and 2-hydroxy-5-nonylbenzaldehyde oxime (LIX860).

[0028] Furthermore, since the technical solution of the present invention does not introduce sodium ions additionally, the raffinate obtained in step S4 can be returned to step S1 for water leaching, achieving recycling. Even further, after multiple cycles, when the concentration of monovalent metal ions in the raffinate reaches a set value, the raffinate is de-oiled and concentrated by evaporation to allow the solute to crystallize out; the concentration and evaporation are preferably MVR evaporation.

[0029] Furthermore, the blank organic phase obtained in step S5 is returned to step S4 for extraction, allowing the extractant to be recycled.

[0030] Furthermore, the lithium compound is lithium carbonate. In step S5, carbonic acid is added to the supported organic phase for back-extraction, yielding a lithium bicarbonate solution and a blank organic phase. In step S6, the lithium bicarbonate solution is de-oiled and then further de-calcified and magnesium-removed. Pyrolysis yields a lithium carbonate slurry and carbon dioxide. The lithium carbonate slurry undergoes solid-liquid separation to obtain lithium carbonate precipitate and mother liquor. The lithium carbonate precipitate is dried to obtain battery-grade lithium carbonate product. Further still, the back-extraction process in step S5 involves mixing carbon dioxide and water to form a carbonic acid solution, which is then used for liquid-liquid two-way back-extraction with the supported organic phase. Alternatively, carbon dioxide and water are continuously introduced to form a gas-liquid-liquid three-way back-extraction with the supported organic phase. Further still, the carbon dioxide obtained in step S6 is returned to step S5 for back-extraction, and the mother liquor is returned to step S3 as a solution for calcium ion removal and / or returned to step S5. Since lithium carbonate is slightly soluble in water, the main component of the mother liquor is dissolved lithium carbonate, with a lithium ion concentration of approximately 2 g / L. The mother liquor can be returned to step S3 as an aqueous solution of carbonate; or it can be returned to step S5, where lithium carbonate reacts with carbon dioxide and water to produce lithium bicarbonate, thus fully recovering the lithium in the mother liquor.

[0031] Furthermore, the lithium compound is lithium carbonate. In step S5, the organic phase is back-extracted with a lithium bicarbonate solution to obtain lithium carbonate and a blank organic phase. Further still, the obtained lithium carbonate is added to water and carbon dioxide, and after reaction, a lithium bicarbonate solution is obtained. The lithium bicarbonate solution is then deoiled and further decalcified to remove calcium and magnesium. Pyrolysis yields a lithium carbonate slurry and carbon dioxide. Solid-liquid separation of the lithium carbonate slurry yields a lithium carbonate precipitate and mother liquor. The lithium carbonate precipitate is dried to obtain a battery-grade lithium carbonate product.

[0032] Furthermore, the lithium compound is lithium hydroxide. In step S5, sulfuric acid is added for back-extraction of the supported organic phase to obtain a lithium sulfate solution and a blank organic phase. In step S6, the lithium sulfate solution is de-oiled and then further de-calcified and demagnesized. Bipolar membrane electrolysis is then performed to obtain a lithium hydroxide solution and sulfuric acid. The lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product. Even further, the sulfuric acid obtained in step S6 is returned to step S5 for back-extraction, allowing the sulfuric acid to be recycled.

[0033] Furthermore, the lithium compound is lithium hydroxide. In step S5, hydrochloric acid is added for back-extraction of the supported organic phase to obtain a lithium chloride solution and a blank organic phase. In step S6, the lithium chloride solution is de-oiled and then further de-calcified and demagnesized. Bipolar membrane electrolysis is then performed to obtain a lithium hydroxide solution and hydrochloric acid. The lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product. Even further, the hydrochloric acid obtained in step S6 is returned to step S5 for back-extraction, allowing the hydrochloric acid to be recycled.

[0034] Furthermore, the lithium compound is lithium chloride. In step S5, hydrochloric acid is added to back-extract the supported organic phase to obtain a lithium chloride solution and a blank organic phase. In step S6, the lithium chloride solution is de-oiled and then further de-calcified and demagnesized, and then evaporated to obtain a battery-grade lithium chloride product.

[0035] Furthermore, in step S4, before extraction, the filtrate B is thoroughly decalcified to remove calcium and magnesium. This thorough decalcification before extraction can prevent calcium and magnesium ions from being transferred into the organic phase during the extraction process.

[0036] Furthermore, in step S1, the lithium ion concentration in the leaching slurry is 0.5~4 g / L. When the lithium ion concentration in the leaching slurry is 0.5~4 g / L, calcium oxide or calcium hydroxide can provide most of the hydroxide ions to provide the driving force for lithium extraction, thereby saving costs.

[0037] In some specific technical solutions, the lithium-containing raw material in step S1 is lepidolite, and the sulfate is one or both of potassium sulfate and calcium sulfate. The raffinate obtained in step S4 is returned to step S1 for water leaching to achieve recycling. After multiple cycles, the potassium ion concentration in the raffinate reaches a set value. The raffinate is then deoiled, concentrated, and evaporated to allow the solute to crystallize and precipitate, yielding potassium sulfate product. In the prior art, during the preparation of lithium compounds from lepidolite, a large amount of sodium ions are introduced, resulting in a mixture of potassium sulfate and sodium sulfate as byproducts. Due to the high cost of separating these two, this mixture can only be treated as a low-value double salt. However, in this invention, since no sodium ions are introduced, the main component of the raffinate is potassium sulfate, ultimately yielding a high-value potassium sulfate product.

[0038] Furthermore, the deep calcium and magnesium removal method described in this invention uses an adsorption resin to adsorb calcium and magnesium.

[0039] The traditional process for preparing lithium carbonate and lithium hydroxide involves the following reaction:

[0040]

[0041] Taking calcium oxide as an example, the reaction for preparing lithium carbonate and lithium hydroxide in this technology can be simplified as follows:

[0042]

[0043] The present invention has the following beneficial technical effects:

[0044] The entire process essentially avoids the introduction of sodium ions, thus preventing the generation of large amounts of low-value sodium sulfate byproducts, the energy-intensive process of separating sodium sulfate, and lithium loss due to lithium entrainment in the sodium sulfate byproduct. The lithium sulfate in the leaching solution is also removed from the system as a product, and the raffinate can be directly recycled for use in the leaching slurry, reducing water consumption. Enriching lithium through extraction and back-extraction eliminates the energy-intensive lithium sulfate concentration process. The main raw materials required are an extractant (which is recyclable with minimal loss) and inexpensive calcium oxide or calcium hydroxide, carbon dioxide (or even industrial waste gas). Inexpensive calcium oxide or calcium hydroxide and carbon dioxide can replace expensive sodium carbonate in lithium carbonate production, and inexpensive calcium oxide and calcium hydroxide can replace expensive sodium hydroxide in lithium hydroxide production. The main byproduct is calcium sulfate, which has a large market application. Compared to existing technologies, this process offers advantages such as low energy consumption, simplified process, low production cost, high product quality, high lithium yield, and convenient byproduct handling. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the process flow of Example 1.

[0046] Figure 2 This is a schematic diagram of the process flow for Example 2.

[0047] Figure 3 This is a schematic diagram of the process flow for Example 3.

[0048] Figure 4 This is a schematic diagram of the process flow for Example 4.

[0049] Figure 5 This is a schematic diagram of the process flow for Example 5. Detailed Implementation

[0050] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, quantity, or position.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Example 1

[0053] A method for preparing battery-grade lithium carbonate, the process flow is as follows: Figure 1 As shown, it includes the following steps.

[0054] S1 involves leaching the clinker obtained from sulfuric acid roasting of spodumene ore with water to produce a leaching slurry. The main active component of the leaching slurry is lithium sulfate, with a lithium ion concentration of 1.5 g / L.

[0055] S2-1 Calcium oxide is added to the leaching slurry to adjust the pH to 6, and the slurry is filtered to obtain filtrate A' and filter residue A'. This step mainly neutralizes the excess sulfuric acid in the leaching slurry. To fully recover the small amount of lithium entrained in filter residue A', filter residue A' is added to water and stirred to form a slurry. The slurry is filtered to obtain residue and washing liquid. The residue (lithium ore slag) is discharged, and the washing liquid is used to wash the filter residue A obtained in S2-2.

[0056] In step S2-2, calcium oxide is added to filtrate A' to adjust the pH to 13.3. After sufficient reaction, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide ions into the system, and removes ferric ions, ferrous ions, and most magnesium ions. The main effective component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching. The main component of filter residue A is calcium sulfate, and it may also contain excess calcium oxide or calcium hydroxide. To fully recover the small amount of lithium entrained in filter residue A, filter residue A is washed with the washing solution from step S2-1. The washing solution is then returned to step S1 for leaching.

[0057] S3. Lithium oxalate is added to filtrate A, and after sufficient reaction, the mixture is filtered to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the dissolved calcium sulfate is converted into water-insoluble calcium oxalate, removing most of the calcium ions. To fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water leaching.

[0058] S4. Filtrate B is subjected to deep calcium and magnesium removal using an adsorption resin, followed by thorough extraction with an extractant to separate the loaded organic phase and raffinate. A composite extractant is formed by mixing Cyanex923 and LIX54, with the volume ratio of Cyanex923 to LIX54 controlled at 2:1. Sulfonated kerosene is used as a diluent, and the composite extractant accounts for 25% of the volume of the extraction system.

[0059] The extraction process separates lithium ions from monovalent metal ions (mainly sodium and potassium). The raffinate is returned to step S1 for water leaching. When the sodium and potassium ion concentrations in the raffinate reach a set value, the raffinate is de-oiled, concentrated, and evaporated to crystallize sodium sulfate and potassium sulfate. The evaporated water is returned to step S2-1 to be used to add filter residue A' to water and stir into a slurry.

[0060] In step S5, the supported organic phase is back-extracted using a lithium bicarbonate solution to obtain lithium carbonate and a blank organic phase. The blank organic phase is then returned to step S4 for extraction. The obtained lithium carbonate is reacted with water and carbon dioxide to obtain a lithium bicarbonate solution (to achieve a lithium ion concentration of approximately 8 g / L). Part of the obtained lithium bicarbonate solution is sent to step S6, and the rest is used for back-extraction of the supported organic phase.

[0061] Step S6 separates the lithium bicarbonate solution from the oil, removes the oil, and then performs deep calcium and magnesium removal. Pyrolysis yields a lithium carbonate slurry and carbon dioxide. The carbon dioxide is returned to step S5 to react with water and carbon dioxide to obtain a lithium bicarbonate solution. Solid-liquid separation of the lithium carbonate slurry yields lithium carbonate precipitate and mother liquor. Since lithium carbonate is slightly soluble in water, the mother liquor mainly consists of dissolved lithium carbonate. The lithium carbonate reacts with carbon dioxide and water to form lithium bicarbonate, allowing for full recovery of lithium from the mother liquor. The lithium carbonate precipitate is dried to obtain solid lithium carbonate, which is then pulverized and packaged to form lithium carbonate products that meet the requirements of the industry standard YS / T582-2023 Battery Grade Lithium Carbonate. After the pyrolysis unit has been running for a period of time, carbon dioxide is introduced into the unit to clean the scale formed by lithium carbonate, converting the lithium carbonate into soluble lithium bicarbonate. Example 2

[0062] A method for preparing battery-grade lithium hydroxide, the process flow is as follows: Figure 2 As shown, it includes the following steps.

[0063] S1 involves passing oxygen and sulfuric acid through waste lithium iron phosphate material, followed by water leaching to obtain a leachate slurry. The main active component of the leachate slurry is lithium sulfate, with a lithium ion concentration of 4 g / L.

[0064] S2-1 Calcium hydroxide is added to the leach slurry to adjust the pH to 5, and the slurry is filtered to obtain filtrate A' and filter residue A'. This step mainly neutralizes the excess sulfuric acid in the leach slurry. To fully recover the small amount of lithium entrained in filter residue A', filter residue A' is added to water and stirred to form a slurry. The slurry is filtered to obtain residue and washing liquid. The residue (ferric phosphate residue) is discharged, and the washing liquid is used to wash the filter residue A obtained in S2-2.

[0065] In step S2-2, calcium hydroxide is added to filtrate A' to adjust the pH to 13.4. After the reaction is complete, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide ions into the system, and removes ferric ions, ferrous ions, and most magnesium ions. The main effective component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching. The main component of filter residue A is calcium sulfate residue, and it may also contain excess calcium oxide or calcium hydroxide. To fully recover the small amount of lithium entrained in filter residue A, filter residue A is washed with the washing solution from step S2-1. The washing solution is then returned to step S1 for leaching.

[0066] S3. Add sodium phosphate to filtrate A, allow it to react completely, and then filter to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the dissolved calcium sulfate is converted into water-insoluble calcium phosphate, removing most of the calcium ions. To fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water leaching.

[0067] S4. Filtrate B is subjected to deep calcium and magnesium removal using an adsorption resin, followed by thorough extraction with an extractant to separate the loaded organic phase and raffinate. TOPO and LIX54 are mixed to form a composite extractant, with the volume ratio of TOPO to LIX54 controlled at 1:1. Sulfonated kerosene is used as a diluent, and the composite extractant accounts for 25% of the volume percentage of the extraction system.

[0068] The extraction process achieves the separation of lithium ions from monovalent metal ions (mainly sodium). The raffinate is returned to step S1 for water leaching. When the sodium ion concentration in the raffinate reaches a set value, the raffinate is de-oiled, concentrated, and evaporated to crystallize sodium sulfate; the evaporated water is returned to step S2-1 to be used to add filter residue A' to water and stir into a slurry.

[0069] In step S5, hydrochloric acid is added for back-extraction of the supported organic phase, yielding a lithium chloride solution and a blank organic phase. The blank organic phase is returned to step S4 for extraction, and the volume ratio of the aqueous phase to the organic phase is controlled during back-extraction to ensure that the lithium ion concentration in the lithium chloride solution after back-extraction reaches above 40 g / L.

[0070] S6 removes oil from the lithium chloride solution and then further removes calcium and magnesium. Bipolar membrane electrolysis yields lithium hydroxide solution and hydrochloric acid. The hydrochloric acid is returned to step S5 for back-extraction. The lithium hydroxide solution is evaporated to obtain lithium hydroxide product, which meets the requirements of industry standard "YS / T 1568-2022 Battery Grade Anhydrous Lithium Hydroxide". The mother liquor obtained from the evaporation of lithium hydroxide solution can be returned to step S3. Example 3

[0071] A method for preparing battery-grade lithium carbonate, the process flow is as follows: Figure 3 As shown, it includes the following steps.

[0072] S1 is a leaching slurry obtained by roasting lepidolite with potassium sulfate and calcium sulfate and then leaching the resulting clinker with water. The main active component of the leaching slurry is lithium sulfate, with a lithium ion concentration of 0.5 g / L.

[0073] S2-1 Add calcium oxide to the leaching slurry to adjust the pH of the leaching slurry to 8.5, and filter to obtain filtrate A' and filter residue A'. In order to fully recover the small amount of lithium entrained in filter residue A', add water to filter residue A' and stir to form a slurry. Filter the slurry to obtain residue and washing liquid. The washing liquid is returned to step S1 for water leaching, and the residue is discharged.

[0074] In step S2-2, calcium oxide is added to filtrate A' to adjust the pH to 12.7. After sufficient reaction, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide ions into the system, and removes ferric ions, ferrous ions, and most of the magnesium ions. The main component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching. The main component of filter residue A is calcium sulfate, and it may also contain excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A and utilize the excess calcium oxide or calcium hydroxide in filter residue A, filter residue A is returned to step S1 for leaching.

[0075] S3. Add the mother liquor obtained in step S6 to filtrate A, and after sufficient reaction, filter to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the addition of the mother liquor obtained in step S6 converts the water-soluble calcium sulfate into water-insoluble calcium carbonate, removing most of the calcium ions. To fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water leaching.

[0076] S4. Filtrate B is subjected to deep calcium and magnesium removal using an adsorption resin, followed by thorough extraction with an extractant to separate the loaded organic phase and raffinate. A composite extractant is formed by mixing Cyanex923 and LIX54, with the volume ratio of Cyanex923 to LIX54 controlled at 2:1. Sulfonated kerosene is used as a diluent, and the composite extractant accounts for 15% of the volume of the extraction system.

[0077] The extraction process achieves the separation of lithium ions from monovalent metal ions (mainly potassium). The raffinate is directly returned to step S1 for water leaching. When the potassium ion concentration in the raffinate reaches a set value, the raffinate is de-oiled, concentrated, and evaporated to crystallize potassium sulfate; the evaporated water is returned to step S2-1 to be used to add filter residue A' to water and stir into a slurry.

[0078] In step S5, carbonic acid is added to the supported organic phase for back-extraction, resulting in a lithium bicarbonate solution and a blank organic phase. During the back-extraction process, carbon dioxide and water are continuously introduced to form a gas-liquid-liquid three-dimensional back-extraction with the supported organic phase. The blank organic phase is returned to step S4 for extraction. The volume ratio of the aqueous phase to the organic phase is controlled during back-extraction to ensure that the lithium ion concentration in the lithium bicarbonate solution after back-extraction reaches approximately 8 g / L.

[0079] S6 removes oil from the lithium bicarbonate solution and then further removes calcium and magnesium. Pyrolysis yields a lithium carbonate slurry and carbon dioxide. The carbon dioxide is returned to step S5 for back-extraction. Figure 3 (Not shown). After the pyrolysis unit has been running for a period of time, in order to clean the scale formed by lithium carbonate inside the unit, carbon dioxide is introduced into the unit to convert lithium carbonate into soluble lithium bicarbonate, such as... Figure 3 As shown by the dashed line, the lithium carbonate slurry undergoes solid-liquid separation to obtain lithium carbonate precipitate and mother liquor. Since lithium carbonate is slightly soluble in water, the main component of the mother liquor is dissolved lithium carbonate. Part of the mother liquor is returned to step S3 as an aqueous solution of carbonates, and part is returned to step S5, where lithium carbonate reacts with carbon dioxide and water to form lithium bicarbonate, thus fully recovering the lithium from the mother liquor. The lithium carbonate precipitate is dried to obtain solid lithium carbonate, which is then subjected to air jet milling and packaging to form lithium carbonate products that meet the requirements of the industry standard YS / T 582-2023 Battery Grade Lithium Carbonate. Example 4

[0080] A method for preparing battery-grade lithium hydroxide, the process flow is as follows: Figure 4 As shown, it includes the following steps.

[0081] S1. The clinker obtained by sulfuric acid roasting of spodumene ore is leached with water to obtain a leaching slurry. The main active component of the leaching slurry is lithium sulfate, with a lithium ion concentration of 3 g / L. During the initial leaching, the sodium ion concentration is approximately 1 g / L, and the potassium ion concentration is approximately 0.5 g / L.

[0082] S2-1 Calcium oxide is added to the leach slurry to adjust the pH to 7.0. The slurry is then filtered to obtain filtrate A' and filter residue A'. This step primarily neutralizes excess sulfuric acid in the leach slurry. To fully recover the small amount of lithium entrained in filter residue A', water is added to filter residue A' and stirred to form a slurry. The slurry is filtered to obtain residue and washing liquid. The washing liquid is returned to step S1 for water leaching, and the residue is discharged.

[0083] In step S2-2, calcium oxide is added to filtrate A' to adjust the pH to 13.0. After sufficient reaction, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide ions into the system, and removes ferric ions, ferrous ions, and most magnesium ions. The main component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching. The main component of filter residue A is calcium sulfate, and it may also contain excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A and to utilize the excess calcium oxide or calcium hydroxide in filter residue A to neutralize sulfuric acid, filter residue A is returned to step S1 for leaching.

[0084] In step S3, sodium carbonate solution is added to filtrate A. After the reaction is complete, the mixture is filtered to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the addition of sodium carbonate solution converts the water-soluble calcium sulfate into water-insoluble calcium carbonate, removing most of the calcium ions. Because the concentration of calcium ions formed by the dissolution of calcium sulfate is very low, very little sodium carbonate is needed, and very little sodium sulfate is generated. To fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water leaching. This operation also allows the calcium carbonate to neutralize the sulfuric acid.

[0085] S4. Filtrate B is subjected to deep removal of calcium and magnesium using adsorption resin, followed by thorough extraction with an extractant. The loaded organic phase and raffinate are then separated. TOPO and LIX860 are mixed to form a composite extractant, with the volume ratio of TOPO to LIX860 controlled at 1:1. Dodecane is used as a diluent, and the composite extractant accounts for 25% of the volume percentage of the extraction system.

[0086] The extraction process achieves the separation of lithium ions from monovalent metal ions (sodium and potassium). The raffinate is directly returned to step S1 for water leaching. After multiple cycles, when the concentration of monovalent metal ions in the raffinate reaches the set value, the raffinate is de-oiled and concentrated and evaporated using MVR (Medium-Volume Resiner) to crystallize the solutes (mainly sodium sulfate and potassium sulfate). The evaporated water is returned to step S2-1 to be used to add filter residue A' to water and stir into a slurry.

[0087] In step S5, sulfuric acid is added for back-extraction of the supported organic phase to obtain a lithium sulfate solution and a blank organic phase. The blank organic phase is returned to step S4 for extraction. The volume ratio of the aqueous phase to the organic phase is controlled during back-extraction to ensure that the lithium ion concentration in the lithium sulfate solution after back-extraction reaches above 25 g / L.

[0088] S6 removes oil from the lithium sulfate solution and then further removes calcium and magnesium. Bipolar membrane electrolysis yields lithium hydroxide solution and sulfuric acid. The sulfuric acid is returned to step S5 for back-extraction. The lithium hydroxide solution is evaporated to obtain lithium hydroxide product, which meets the requirements of industry standard "YS / T 1568-2022 Battery Grade Anhydrous Lithium Hydroxide". The mother liquor obtained from the evaporation of lithium hydroxide solution can be returned to step S3. Example 5

[0089] A method for preparing battery-grade lithium chloride, the process flow is as follows: Figure 5 As shown, it includes the following steps.

[0090] S1 involves reacting waste lithium iron phosphate material with hydrogen peroxide and sulfuric acid, followed by water leaching to obtain a leachate slurry. The main active component of the leachate slurry is lithium sulfate, with a lithium ion concentration of 1.0 g / L.

[0091] S2-1 Calcium oxide is added to the leach slurry to adjust the pH to 6.5, and the slurry is filtered to obtain filtrate A' and filter residue A'. This step mainly neutralizes the excess sulfuric acid in the leach slurry. To fully recover the small amount of lithium entrained in filter residue A', filter residue A' is added to water and stirred to form a slurry. The slurry is filtered to obtain residue and washing liquid. The washing liquid is returned to step S1 for water leaching, and the residue is discharged.

[0092] In step S2-2, calcium oxide is added to filtrate A' to adjust the pH to 13.5. After sufficient reaction, the mixture is filtered to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide ions into the system, and removes ferric ions, ferrous ions, and most magnesium ions. The main component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching. The main component of filter residue A is calcium sulfate, and it may also contain excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A and to utilize the excess calcium oxide or calcium hydroxide in filter residue A to neutralize sulfuric acid, filter residue A is returned to step S1 for leaching.

[0093] In step S3, sodium carbonate solution is added to filtrate A. After sufficient reaction, the mixture is filtered to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the addition of sodium carbonate solution converts the dissolved calcium sulfate into sparingly soluble calcium carbonate, removing most of the calcium ions. Because the concentration of calcium ions formed by the dissolution of calcium sulfate is very low, very little sodium carbonate is needed, and very little sodium sulfate is generated. To fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water leaching. This operation also allows the calcium carbonate to neutralize the sulfuric acid.

[0094] S4. Filtrate B is subjected to deep removal of calcium and magnesium using an adsorption resin, followed by thorough extraction with an extractant, resulting in the separation of the loaded organic phase and raffinate. TBP and LIX84 are mixed to form a composite extractant, with the volume ratio of TBP to LIX84 controlled at 0.2:1. Sulfonated kerosene is used as a diluent, and the composite extractant constitutes 20% of the extraction system by volume.

[0095] The extraction process achieves the separation of lithium ions from monovalent metal ions (sodium and potassium). The raffinate is directly returned to step S1 for water leaching. After multiple cycles, when the concentration of monovalent metal ions in the raffinate reaches the set value, the raffinate is de-oiled and concentrated and evaporated using MVR (Medium-Voltage Reduction) to crystallize the solute. The evaporated water is returned to step S2 for adding water and stirring the filter residue A'.

[0096] In step S5, hydrochloric acid is added for back-extraction of the supported organic phase, yielding a lithium chloride solution and a blank organic phase. The blank organic phase is returned to step S4 for extraction, and the volume ratio of the aqueous phase to the organic phase is controlled during back-extraction to ensure that the lithium ion concentration in the lithium chloride solution after back-extraction reaches above 50 g / L.

[0097] S6 removes oil from the lithium chloride solution and then further removes calcium and magnesium. The resulting lithium chloride product is then evaporated and meets the requirements of the industry standard "YS / T744-2010 Battery Grade Anhydrous Lithium Chloride". The mother liquor obtained from the evaporation of the lithium chloride solution can be returned to step S3.

[0098] Although embodiments of the present invention have been shown and described above, it is understood that these embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention without departing from its principles and spirit. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing battery-grade lithium compounds, characterized in that, Includes the following steps: S1 involves acidifying the lithium-containing raw material with sulfuric acid or roasting it with sulfate, followed by water leaching to obtain a leachate slurry; the lithium-containing raw material is lithium mineral or waste lithium battery material. S2-1 Add an appropriate amount of calcium oxide or calcium hydroxide to the leachate to neutralize the excess acid in the leachate. After the neutralization reaction is complete, filter to obtain filtrate A' and filter residue A'. Control the amount of calcium oxide or calcium hydroxide added so that the pH value of filtrate A' is 4.0~11.

9. S2-2 Add calcium oxide or calcium hydroxide to filtrate A', and after the reaction is complete, filter to obtain filtrate A and filter residue A; control the amount of calcium oxide or calcium hydroxide added so that the pH value of filtrate A is 12.7~13.5; the main component of filtrate A is lithium hydroxide, and it also includes soluble impurities formed after water leaching; S3 Add a substance to remove calcium ions to filtrate A, react fully, and then filter to obtain filtrate B and filter residue B; S4. The filtrate B is fully contacted with the extractant for extraction, and then the loaded organic phase and raffinate are separated. S5 involves back-extraction of the supported organic phase to obtain a lithium solution and a blank organic phase; S6 further processes the lithium solution to obtain battery-grade lithium compounds.

2. The method according to claim 1, characterized in that, Step S2-1 controls the amount of calcium oxide or calcium hydroxide added so that the pH of filtrate A' is 6.5~7.

5.

3. The method according to claim 1, characterized in that, Add filter residue A' to water and stir to form a slurry. Filter the slurry to obtain residue and washing liquid. Discharge the residue. Wash filter residue A with the washing liquid. Discharge the washed filter residue A. Return the washing liquid to step S1 for water immersion.

4. The method according to claim 1, characterized in that, The calcium ion-removing substance mentioned in step S3 is selected from one or more of the following: carbonate, aqueous solution of carbonate, oxalate, aqueous solution of oxalate, phosphate, and aqueous solution of phosphate.

5. The method according to claim 1, characterized in that, Return the filter residue B obtained in step S3 to step S1 for water immersion.

6. The method according to claim 1, characterized in that, The extractant in step S4 is a composite extractant, comprising a neutral extractant and a chelating extractant. The extraction system also includes a diluent. The neutral extractant comprises one or more of the following: tributyl phosphate, dimethylheptyl methyl phosphate, trioctylphosphine oxide, trioctyl / hexylphosphine oxide, and N,N-di-(1-methylheptyl)acetamide. The chelating extractant comprises one or more of the following: 2-hydroxy-5-nonylacetophenone oxime, dodecylphenyl-methyl-β-dione, and 2-hydroxy-5-nonylbenzaldehyde oxime.

7. The method according to claim 1, characterized in that, The raffinate obtained in step S4 is returned to step S1 for water immersion to achieve recycling.

8. The method according to claim 7, characterized in that, After multiple cycles, when the concentration of monovalent metal ions in the raffinate reaches the set value, the raffinate is de-oiled, concentrated, and evaporated to allow the solute to crystallize and precipitate.

9. The method according to claim 8, characterized in that, The concentration evaporation is MVR evaporation.

10. The method according to claim 1, characterized in that, The blank organic phase obtained in step S5 is returned to step S4 for extraction.

11. The method according to claim 1, characterized in that, The lithium compound is lithium carbonate. In step S5, carbonic acid is added to back-extract the supported organic phase to obtain a lithium bicarbonate solution and a blank organic phase. In step S6, the lithium bicarbonate solution is de-oiled and then deeply de-calcified and magnesium-removed. Pyrolysis is performed to obtain lithium carbonate slurry and carbon dioxide. The lithium carbonate slurry is separated into solid and liquid phases to obtain lithium carbonate precipitate and mother liquor. The lithium carbonate precipitate is dried to obtain battery-grade lithium carbonate product.

12. The method according to claim 11, characterized in that Step S5 back-extraction process involves mixing carbon dioxide and water to form a carbonic acid solution, which is then used to form a liquid-liquid two-way back-extraction with the supported organic phase, or continuously introducing carbon dioxide and water to form a gas-liquid-liquid three-way back-extraction with the supported organic phase.

13. The method according to claim 11, characterized in that, The carbon dioxide obtained in step S6 is returned to step S5 for back-extraction, and the mother liquor is returned to step S3 as a substance for removing calcium ions and / or returned to step S5.

14. The method according to claim 1, characterized in that, The lithium compound is lithium carbonate. In step S5, the organic phase is back-extracted with a lithium bicarbonate solution to obtain lithium carbonate and a blank organic phase.

15. The method according to claim 14, characterized in that, The obtained lithium carbonate is added to water and carbon dioxide, and after reaction, a lithium bicarbonate solution is obtained. The lithium bicarbonate solution is deoiled and then subjected to further calcium and magnesium removal. Pyrolysis is performed to obtain lithium carbonate slurry and carbon dioxide. Solid-liquid separation of the lithium carbonate slurry is performed to obtain lithium carbonate precipitate and mother liquor. The lithium carbonate precipitate is dried to obtain battery-grade lithium carbonate product.

16. The method according to claim 1, characterized in that, The lithium compound is lithium hydroxide. In step S5, sulfuric acid is added to back-extract the supported organic phase to obtain a lithium sulfate solution and a blank organic phase. In step S6, the lithium sulfate solution is de-oiled and then deeply de-calcified and demagnesified. Bipolar membrane electrolysis is used to obtain a lithium hydroxide solution and sulfuric acid. The lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product.

17. The method according to claim 16, characterized in that, The sulfuric acid obtained in step S6 is returned to step S5 for back-extraction.

18. The method according to claim 1, characterized in that, The lithium compound is lithium hydroxide. In step S5, hydrochloric acid is added to back-extract the supported organic phase to obtain a lithium chloride solution and a blank organic phase. In step S6, the lithium chloride solution is de-oiled and then deeply de-calcified and demagnesized. Bipolar membrane electrolysis is used to obtain a lithium hydroxide solution and hydrochloric acid. The lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product.

19. The method according to claim 18, characterized in that, The hydrochloric acid obtained in step S6 is returned to step S5 for back-extraction.

20. The method according to claim 1, characterized in that, The lithium compound is lithium chloride. In step S5, hydrochloric acid is added to back-extract the supported organic phase to obtain a lithium chloride solution and a blank organic phase. In step S6, the lithium chloride solution is de-oiled and then further de-calcified and demagnesified, and evaporated to obtain a battery-grade lithium chloride product.

21. The method according to claim 1, characterized in that, Step S4 involves thoroughly removing calcium and magnesium from filtrate B before extraction.

22. The method according to claim 1, characterized in that, In step S1, the lithium ion concentration in the leaching slurry is 0.5~4 g / L.

23. The method according to claim 1, characterized in that, The lithium-containing raw material in step S1 is lepidolite, and the sulfate is one or both of potassium sulfate and calcium sulfate. The raffinate obtained in step S4 is returned to step S1 for water leaching to achieve recycling. After multiple cycles, the potassium ion concentration in the raffinate reaches the set value. The raffinate is then de-oiled, concentrated, and evaporated to allow the solute to crystallize and precipitate, thus obtaining the potassium sulfate product.

24. The method according to claim 11, 15, 16, 18, 20, or 21, characterized in that, The deep removal of calcium and magnesium involves adsorbing calcium and magnesium using an adsorption resin.

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