CN118619314A - A method for preparing battery-grade lithium compounds - Google Patents

Abstract

The invention discloses a method for preparing a battery-grade lithium compound, which belongs to the technical field of lithium compound preparation methods, and comprises the following steps: S1, sulfuric acid acidification reaction of lithium-containing raw materials or adding sulfate roasting, water leaching to obtain leaching slurry; the lithium-containing raw materials are lithium minerals or waste lithium battery materials; S2, calcium oxide or calcium hydroxide is added to the leaching slurry, and filtered after sufficient reaction to obtain filtrate A and filter residue A; S3, a substance for removing calcium ions is added to the filtrate A, and filtered after sufficient reaction to obtain filtrate B and filter residue B; S4, filtrate B is fully contacted with an extractant for extraction, and then separated to obtain a loaded organic phase and a raffinate; S5, the loaded organic phase is reversely extracted to obtain a lithium solution and a blank organic phase; S6, the lithium solution is further processed to obtain a battery-grade lithium compound. The invention basically does not introduce sodium ions, and has the advantages of low energy consumption, simplified process, high product quality, low production cost, high lithium yield, and convenient treatment of by-products.

Description

A method for preparing battery-grade lithium compounds

Technical Field

The invention belongs to the technical field of lithium compound preparation methods and relates to a method for preparing battery-grade lithium compounds.

Background Art

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 increasingly valued. Battery-grade lithium compounds mainly include lithium carbonate, lithium hydroxide and lithium chloride, among which lithium carbonate is the largest, accounting for more than 60% of the total amount of battery-grade lithium compounds.

Lithium minerals and waste lithium batteries are important lithium-containing raw materials. The current common process is to add sulfuric acid to these raw materials for acidification reaction or sulfate roasting, and then leaching to obtain a leachate with lithium sulfate as the main component (lithium ion concentration is about 5-13g/L), and then obtain lithium products through subsequent processes. For example, CN109371227A discloses a sulfuric acid method for extracting lithium from spodumene magnetic materials, in which a saturated sodium hydroxide solution is added to the lithium sulfate solution obtained by sulfuric acid acidification and roasting, the pH is adjusted, and a pure lithium hydroxide solution is obtained after precipitation and filtration; the pure lithium hydroxide solution is evaporated and concentrated to obtain a lithium hydroxide solution with a concentration of 20%, and then a saturated sodium carbonate solution is added to obtain a lithium carbonate precipitate; the lithium carbonate precipitate is filtered and washed, and then vacuum dried to obtain a lithium carbonate product.

CN102311110A discloses a complete set of cyclic preparation methods for producing lithium ferrous phosphate using lithium ore as a lithium source, wherein the lithium ore is calcined, acidified, leached, purified and separated to obtain a primary lithium liquid, the primary lithium liquid is converted and frozen, filtered, washed, evaporated and concentrated to obtain a lithium liquid for synthesis reaction, the lithium liquid for synthesis reaction is subjected to a liquid phase synthesis reaction with a ferrous salt solution and a phosphorus source solution, and calcined to obtain carbon-coated lithium ferrous phosphate. "Conversion and freezing" means that a sodium salt is added to the primary lithium liquid, Li ₂ SO ₄ in the primary lithium liquid reacts with the sodium salt to produce another lithium salt and Na ₂ SO ₄ , the solution is cooled to allow the generated sodium sulfate to crystallize and precipitate, and then removed by solid-liquid separation.

CN115537551A discloses a method for preferentially extracting lithium and manganese from waste lithium battery positive electrode materials. First, sulfation roasting is used to convert lithium and manganese into lithium sulfate and manganese sulfate. The roasted material is leached into a solution by water leaching, and a small amount of nickel sulfate and cobalt sulfate exist in the solution. A certain amount of sodium sulfate is added to the solution to remove nickel and cobalt ions in the solution. After precipitating manganese ions in the solution with calcium hydroxide or calcium oxide, sodium carbonate is added to the solution to synthesize lithium carbonate. Reduction acid leaching is used to separate manganese hydroxide and calcium sulfate, and manganese sulfate is concentrated and crystallized to generate manganese sulfate.

It can be seen that although the specific technical solutions have their own characteristics, the existing technology generally needs to add sodium hydroxide and/or sodium salt (mainly sodium carbonate) to introduce a large amount of sodium ions into the reaction system after obtaining the leachate with lithium sulfate as the main component. This leads to at least three adverse consequences: on the one hand, a large amount of low-value sodium sulfate by-product is difficult to digest (China's annual demand for sodium sulfate is only about 15 million tons. The sodium sulfate by-product of China's lithium salt industry is close to 1 million tons, and the sodium sulfate by-product of China's lithium battery industry is close to 2 million tons, and both are still increasing rapidly), which constitutes environmental pressure; on the other hand, in order to separate the sodium sulfate, high-energy consumption methods such as evaporation concentration or freezing crystallization are required; on the other hand, the by-product sodium sulfate carries lithium, resulting in lithium loss.

In addition, many existing technologies produce industrial-grade lithium compounds. Compared with industrial-grade lithium compounds, battery-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 the existing technology requires the addition of corresponding impurity removal measures to ensure sufficient removal, further increasing production costs.

Summary of the invention

The purpose of the present invention is to provide a method for preparing battery-grade lithium compounds. After lithium minerals or waste lithium battery materials are subjected to sulfuric acid acidification reaction or sulfate roasting, and water leaching to obtain a leaching slurry with lithium sulfate as the main component, calcium oxide or calcium hydroxide is added to provide hydroxide, lithium is enriched by extraction and lithium is separated from other monovalent metal ions, and after obtaining a lithium extract, corresponding material stripping and subsequent process flow are adopted according to the type of the final lithium compound; the entire process flow basically does not introduce sodium ions, thereby avoiding the generation of low-value sodium sulfate by-products, the high energy consumption operation process of separating sodium sulfate, and the lithium loss caused by the entrainment of lithium in the by-product sodium sulfate, and the raffinate can be directly circulated for leaching slurry to reduce Water consumption; lithium enrichment is achieved through extraction and stripping, avoiding the high energy consumption lithium sulfate concentration process; the raw materials that need to be added are mainly extractants (the extractants can be recycled with little loss) and cheap calcium oxide or calcium hydroxide, carbon dioxide (even industrial tail gas can be used), etc., cheap calcium oxide or calcium hydroxide and carbon dioxide are used to replace expensive sodium carbonate to prepare lithium carbonate, and cheap calcium oxide or calcium hydroxide is used to replace expensive sodium hydroxide to prepare lithium hydroxide. The by-product obtained is mainly calcium sulfate with a large application scale (China's annual demand for calcium sulfate is about 150 million tons); compared with the prior art, it has the advantages of low energy consumption, simplified process, low production cost, high product quality, high lithium yield, and convenient treatment of by-products. The purpose of the present invention is achieved through the following specific technical solutions.

A method for preparing a battery-grade lithium compound comprises the following steps:

S1: The lithium-containing raw material is subjected to sulfuric acid acidification reaction or sulfate roasting, and then water-leached to obtain a leaching slurry; the lithium-containing raw material is a lithium mineral or waste lithium battery material. The main active ingredient of the leaching slurry is lithium sulfate.

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

S3 Add calcium ion removal substances to the filtrate A, filter after sufficient reaction, and obtain filtrate B and filter residue B. This step is to remove the calcium ions introduced by adding calcium oxide or calcium hydroxide, and the calcium ions after calcium sulfate is slightly dissolved in water, forming an insoluble calcium precipitate.

S4: The filtrate B is fully contacted with the extractant for extraction, and then separated to obtain a loaded organic phase and a raffinate.

S5 reversely extracts the loaded organic phase to obtain a lithium solution and a blank organic phase. Through the extraction and reverse extraction process, the separation of lithium ions and monovalent metal ions (sodium and potassium) is achieved, and the enrichment of lithium ions is also achieved.

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

Furthermore, the amount of calcium oxide or calcium hydroxide added is controlled so that the pH value of the filtrate A is 12.0-14.0. Within this pH value range, most of the lithium sulfate can be converted into lithium hydroxide, avoiding the use of sodium hydroxide which is more expensive than calcium oxide or calcium hydroxide.

In some specific technical solutions, step S2 is decomposed into two steps:

S2-1 Adding an appropriate amount of calcium oxide or calcium hydroxide to the leaching slurry to neutralize the excess acid in the leaching slurry, filtering after the neutralization reaction is completed to obtain a filtrate A' and a filter residue A';

S2-2 Add calcium oxide or calcium hydroxide to the filtrate A', filter after sufficient reaction, and obtain filtrate A and filter residue A.

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

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

Furthermore, in order to fully recover the filter residue A' and a small amount of lithium entrained in the filter residue A, the filter residue A' is added with water and stirred into a slurry, the slurry is filtered to obtain a residue and a washing liquid, the residue (mainly lithium mineral slag or waste lithium battery material slag) is discharged, and the residue after sufficient washing hardly entrains lithium; the washing liquid is then used to wash the filter residue A, the washed filter residue A (mainly calcium sulfate slag) is discharged, and the washing liquid after washing is returned to step S1 for water immersion.

By decomposing step S2 into two steps, the lithium mineral slag or waste lithium battery material slag is separated from the calcium sulfate slag as much as possible. In addition, the pH value of the filtrate A' after the neutralization reaction is low, and the pH value of the washing liquid after washing the filter residue A' is low. Correspondingly, the pH value of the discharged slag is also low. Since the higher the pH value of the slag, the more extractant is taken away, the extractant taken away by the discharged slag after the raffinate is circulated and leached can be as little as possible.

Furthermore, the substance for removing calcium ions in step S3 is selected from one or more of carbonate, an aqueous solution of carbonate, oxalate, an aqueous solution of oxalate, phosphate, and an aqueous solution of phosphate.

Since calcium sulfate is slightly soluble in water, by adding calcium ion removing substances, the calcium sulfate dissolved in water is converted into calcium carbonate, calcium oxalate or calcium phosphate which are insoluble in water (the solubility product of calcium sulfate is 9.1×10 ^-6 , the solubility product of calcium carbonate is 3.36×10 ^-9 , the solubility product of calcium oxalate is 4×10 ^-9 , and the solubility product of calcium phosphate is 2.0×10 ^-29 ), thus removing most of the calcium ions.

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

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

Furthermore, since the technical solution of the present invention does not introduce additional sodium ions, the raffinate obtained in step S4 can be returned to step S1 for water immersion to achieve recycling. Furthermore, when the concentration of monovalent metal ions in the raffinate reaches a set value after multiple cycles, the raffinate is deoiled and concentrated and evaporated to crystallize the solute; the concentrated evaporation is preferably MVR evaporation.

Furthermore, the blank organic phase obtained in step S5 is returned to step S4 for extraction, so that the extractant can be recycled.

Further, the lithium compound is lithium carbonate, and step S5 adds carbonic acid to strip the loaded organic phase to obtain a lithium bicarbonate solution and a blank organic phase; step S6 removes oil from the lithium bicarbonate solution and deeply removes calcium and magnesium, pyrolyzes to obtain lithium carbonate slurry and carbon dioxide, and the lithium carbonate slurry is solid-liquid separated to obtain lithium carbonate precipitation and mother liquor, and the lithium carbonate precipitation is dried to obtain a battery-grade lithium carbonate product. Further, the stripping process of step S5 is to mix carbon dioxide and water to form a carbonic acid solution and then form a liquid-liquid two-phase extraction with the loaded organic phase, or to continuously pass carbon dioxide and water into the loaded organic phase to form a gas-liquid-liquid three-phase extraction. Further, the carbon dioxide obtained in step S6 returns to step S5 for stripping, and the mother liquor returns to step S3 as a solution for removing calcium ions and/or returns to step S5. Since lithium carbonate is slightly soluble in water, the main component of the mother liquor is dissolved lithium carbonate, and the lithium ion concentration in the mother liquor is about 2g/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 generate lithium bicarbonate, so that the lithium in the mother liquor can be fully recovered.

Furthermore, the lithium compound is lithium carbonate, and step S5 uses lithium bicarbonate solution to strip the organic phase to obtain lithium carbonate and a blank organic phase. Furthermore, water and carbon dioxide are added to the obtained lithium carbonate to obtain a lithium bicarbonate solution after reaction, and the lithium bicarbonate solution is deoiled and deeply decalcified and magnesium is removed, and pyrolysis is performed to obtain lithium carbonate slurry and carbon dioxide, and the lithium carbonate slurry is solid-liquid separated to obtain lithium carbonate precipitate and mother liquor, and the lithium carbonate precipitate is dried to obtain a battery-grade lithium carbonate product.

Furthermore, the lithium compound is lithium hydroxide, sulfuric acid is added to strip the loaded organic phase in step S5 to obtain a lithium sulfate solution and a blank organic phase; step S6 removes oil from the lithium sulfate solution and deeply removes calcium and magnesium, and bipolar membrane electrolysis is performed to obtain a lithium hydroxide solution and sulfuric acid, and the lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product. Furthermore, the sulfuric acid obtained in step S6 is returned to step S5 for stripping, so that the sulfuric acid can be recycled.

Furthermore, the lithium compound is lithium hydroxide, and hydrochloric acid is added to strip the loaded organic phase in step S5 to obtain a lithium chloride solution and a blank organic phase; and in step S6, the lithium chloride solution is deoiled and calcium and magnesium are deeply removed, and bipolar membrane electrolysis is performed to obtain a lithium hydroxide solution and hydrochloric acid, and the lithium hydroxide solution is evaporated to obtain a battery-grade lithium hydroxide product. Furthermore, the hydrochloric acid obtained in step S6 is returned to step S5 for stripping, so that the hydrochloric acid can be recycled.

Furthermore, the lithium compound is lithium chloride, and step S5 adds hydrochloric acid to strip the loaded organic phase to obtain a lithium chloride solution and a blank organic phase; step S6 removes oil from the lithium chloride solution and deeply removes calcium and magnesium, and evaporates to obtain a battery-grade lithium chloride product.

Furthermore, in step S4, before extraction, the filtrate B is deeply decalcified and magnesiumized. The deep decalcification and magnesiumization before extraction can avoid the transfer of calcium ions and magnesium ions into the organic phase during the extraction process.

Furthermore, the lithium ion concentration in the leached slurry in step S1 is 0.5-4 g/L. When the lithium ion concentration in the leached slurry is 0.5-4 g/L, calcium oxide or calcium hydroxide can provide most of the hydroxide to provide the driving force for extracting lithium, thereby saving costs.

In some specific technical schemes, 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 immersion to achieve recycling. When the potassium ion concentration in the raffinate reaches a set value after multiple cycles, the raffinate is deoiled and concentrated and evaporated to crystallize the solute to obtain a potassium sulfate product. In the prior art, in the process of preparing lithium compounds using lepidolite as a raw material, a large amount of sodium ions are introduced, and the final by-product is a mixture of potassium sulfate and sodium sulfate. Due to the high separation cost of the two, the mixture can only be treated as a low-value double salt; however, in the present invention, since no sodium ions are introduced, the main component of the raffinate is potassium sulfate, and a high-value potassium sulfate product can be obtained in the end.

Furthermore, the deep removal of calcium and magnesium in the present invention is to adsorb calcium and magnesium with adsorption resin.

The traditional process for preparing lithium carbonate and lithium hydroxide is as follows:

Taking calcium oxide as an example, the reaction of preparing lithium carbonate and lithium hydroxide in this technical process can be simplified as follows:

The present invention has the following beneficial technical effects:

Basically, no sodium ions are introduced into the whole process flow, thereby avoiding the production of a large amount of low-value sodium sulfate by-product, the high energy consumption operation process of separating sodium sulfate, and the lithium loss caused by the entrainment of lithium in the by-product sodium sulfate. The lithium sulfate in the leaching solution is also converted into a product out of the system, and the raffinate can be directly recycled for leaching slurry to reduce water consumption. The enrichment of lithium through extraction and stripping can eliminate the high energy consumption lithium sulfate concentration process. The raw materials that need to be added are mainly extractants (the extractants can be recycled with little loss) and inexpensive calcium oxide or calcium hydroxide, carbon dioxide (even industrial tail gas can be used), etc. Cheap calcium oxide or calcium hydroxide and carbon dioxide are used to replace expensive sodium carbonate to prepare lithium carbonate, and cheap calcium oxide and calcium hydroxide are used to replace expensive sodium hydroxide to prepare lithium hydroxide. The by-product obtained is mainly calcium sulfate with a large application scale. Compared with the existing technology, it has the advantages of low energy consumption, simplified process, low production cost, high product quality, high lithium yield, and convenient treatment of by-products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the process flow of Example 1.

FIG. 2 is a schematic diagram of the process flow of Example 2.

FIG3 is a schematic diagram of the process flow of Example 3.

FIG. 4 is a schematic diagram of the process flow of Example 4.

FIG5 is a schematic diagram of the process flow of Example 5.

DETAILED DESCRIPTION

The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings of the specification. Obviously, the described implementation is only a part of the implementation of the present invention, not all of the implementations. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

In the description of the present invention, it is necessary to understand that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance, quantity or position.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Example 1

A method for preparing battery-grade lithium carbonate, the process flow is shown in Figure 1, and includes the following steps.

S1: The clinker obtained by acidifying and roasting the spodumene ore with sulfuric acid is leached with water to obtain a leaching slurry. The main active ingredient of the leaching slurry is lithium sulfate, and the lithium ion concentration is 1.5g/L.

S2-1 Add calcium oxide to the leaching slurry, adjust the pH value of the leaching slurry to 6, and filter to obtain filtrate A' and filter residue A'. This step is mainly to neutralize the excess sulfuric acid in the leaching slurry. In order to fully recover the small amount of lithium entrained in the filter residue A', the filter residue A' is added with water and stirred into 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.

S2-2 adds calcium oxide to the filtrate A', adjusts the pH value to 13.3, and filters after sufficient reaction to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide into the system, and removes iron ions, ferrous ions and most magnesium ions. The main effective component of filtrate A is lithium hydroxide, and also includes soluble impurities formed after water immersion; the main component of filter residue A is calcium sulfate, and there may be excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A, the filter residue A is washed with the washing liquid of S2-1, and the washing liquid after washing is returned to step S1 for leaching.

S3: Add lithium oxalate to the filtrate A, and filter after sufficient reaction to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the calcium sulfate dissolved in water is converted into calcium oxalate which is insoluble in water, and most of the calcium ions are removed. In order to fully recover the small amount of lithium entrained in the filter residue B, the filter residue B is returned to step S1 for water leaching.

S4 The filtrate B is deeply decalcified and magnesiumized by using an adsorption resin, and then fully contacted with the extractant for extraction, and the loaded organic phase and the raffinate are separated. Cyanex923 and LIX54 are mixed to form a composite extractant, and the volume ratio of Cyanex923 to LIX54 is controlled to be 2:1, sulfonated kerosene is used as a diluent, and the volume percentage of the composite extractant in the extraction system is 25%.

Through the extraction process, the separation of lithium ions and monovalent metal ions (mainly sodium and potassium) is achieved. The raffinate is returned to step S1 for water immersion. When the sodium and potassium ion concentrations in the raffinate reach the set value, the raffinate is deoiled and concentrated and evaporated to crystallize sodium sulfate and potassium sulfate; the evaporated water is returned to step S2-1 and used to add water to the filter residue A' and stir it into a slurry.

S5: The loaded organic phase is back-extracted with a lithium bicarbonate solution to obtain lithium carbonate and a blank organic phase, and the blank organic phase is returned to step S4 for extraction. The obtained lithium carbonate is added to water and carbon dioxide for reaction to obtain a lithium bicarbonate solution (so that the lithium ion concentration in the lithium bicarbonate solution reaches about 8 g/L), and a portion of the obtained lithium bicarbonate solution enters S6, and a portion is used for back-extraction of the loaded organic phase.

S6 separates the lithium bicarbonate solution from the oil and removes the oil to deeply remove calcium and magnesium, and pyrolyzes to obtain lithium carbonate slurry and carbon dioxide. The carbon dioxide returns to step S5 to add lithium carbonate to water and carbon dioxide to react to obtain lithium bicarbonate solution. The solid-liquid separation of the lithium carbonate slurry obtains 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. Lithium carbonate reacts with carbon dioxide and water to form lithium bicarbonate, so that the lithium in the mother liquor can be fully recovered. The lithium carbonate precipitate is dried to obtain lithium carbonate solid, which is then crushed and packaged by air flow to form a lithium carbonate product, which meets the requirements of the industry standard "YS/T582-2023 Battery Grade Lithium Carbonate". After the pyrolysis device has been running for a period of time, in order to clean the scaling formed by lithium carbonate in the device, carbon dioxide is introduced into the device to convert lithium carbonate into soluble lithium bicarbonate.

Example 2

A method for preparing battery-grade lithium hydroxide, the process flow is shown in Figure 2, and includes the following steps.

S1 passes oxygen and sulfuric acid through the waste lithium iron phosphate material for acidification reaction, and then leaches with water to obtain a leaching slurry. The main active ingredient of the leaching slurry is lithium sulfate, and the lithium ion concentration is 4g/L.

S2-1 Add calcium hydroxide to the leaching slurry, adjust the pH value of the leaching slurry to 5, and filter to obtain filtrate A' and filter residue A'. This step is mainly to neutralize the excess sulfuric acid in the leaching slurry. In order to fully recover the small amount of lithium entrained in the filter residue A', the filter residue A' is added with water and stirred into a slurry. The slurry is filtered to obtain residue and washing liquid. The residue (iron phosphate residue) is discharged, and the washing liquid is used to wash the filter residue A obtained in S2-2.

S2-2 adds calcium hydroxide to the filtrate A', adjusts the pH value to 13.4, and filters after sufficient reaction to obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide into the system, and removes iron ions, ferrous ions and most of magnesium ions. The main effective component of filtrate A is lithium hydroxide, and also includes soluble impurities formed after water immersion; the main component of filter residue A is calcium sulfate residue, and there may be excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A, the filter residue A is washed with the washing liquid of S2-1, and the washing liquid after washing is returned to step S1 for leaching.

S3: Sodium phosphate is added to the filtrate A, and after sufficient reaction, it is filtered to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, the calcium sulfate dissolved in water is converted into calcium phosphate which is insoluble in water, and most of the calcium ions are removed. In order to fully recover the small amount of lithium entrained in the filter residue B, the filter residue B is returned to step S1 for water leaching.

S4 The filtrate B is deeply decalcified and magnesiumized by using an adsorption resin, and then fully contacted with the extractant for extraction, and the loaded organic phase and the raffinate are separated. TOPO and LIX54 are mixed to form a composite extractant, and the volume ratio of TOPO to LIX54 is controlled to be 1:1, sulfonated kerosene is used as a diluent, and the volume percentage of the composite extractant in the extraction system is 25%.

Through the extraction process, the separation of lithium ions and monovalent metal ions (mainly sodium) is achieved. The raffinate is returned to step S1 for water immersion. When the sodium ion concentration in the raffinate reaches the set value, the raffinate is deoiled and concentrated and evaporated to crystallize sodium sulfate; the evaporated water is returned to step S2-1 and used to add water to the filter residue A' and stir it into slurry.

S5 adds hydrochloric acid to strip the loaded organic phase to obtain 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 during stripping is controlled so that the lithium ion concentration in the lithium chloride solution after stripping reaches 40 g/L or more.

S6 removes oil from the lithium chloride solution and deeply removes calcium and magnesium, and performs bipolar membrane electrolysis to obtain lithium hydroxide solution and hydrochloric acid. The hydrochloric acid is returned to step S5 for stripping, and the lithium hydroxide solution is evaporated to obtain a lithium hydroxide product, which meets the requirements of the industry standard "YS/T 1568-2022 Battery Grade Anhydrous Lithium Hydroxide". The mother liquor obtained by evaporating the lithium hydroxide solution can be returned to step S3.

Example 3

A method for preparing battery-grade lithium carbonate, the process flow is shown in Figure 3, and includes the following steps.

S1 The clinker obtained by roasting lepidolite with potassium sulfate and calcium sulfate is leached with water to obtain a leaching slurry. The main active ingredient of the leaching slurry is lithium sulfate, and the lithium ion concentration is 0.5g/L.

S2-1 Calcium oxide is added to the leaching slurry, the pH value of the leaching slurry is adjusted to 8.5, and the filtrate A' and the filter residue A' are obtained by filtration. In order to fully recover the small amount of lithium entrained in the filter residue A', the filter residue A' is added with water and stirred into slurry, and the slurry is filtered to obtain residue and washing liquid, and the washing liquid is returned to step S1 for water leaching, and the residue is discharged.

S2-2 Add calcium oxide to the filtrate A', adjust the pH value to 12.7, filter after sufficient reaction, and obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide into the system, and removes iron ions, ferrous ions and most of magnesium ions. The main component of filtrate A is lithium hydroxide, and also includes soluble impurities formed after water immersion; the main component of filter residue A is calcium sulfate, and there may be 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.

S3: Add the mother liquor obtained in step S6 to the filtrate A, and filter after sufficient reaction to obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, calcium sulfate dissolved in water is converted into calcium carbonate insoluble in water by adding the mother liquor obtained in step S6, and most of the calcium ions are removed. In order to fully recover a small amount of lithium entrained in the filter residue B, the filter residue B is returned to step S1 for water leaching.

S4 The filtrate B is deeply decalcified and magnesiumized by adsorption resin, and then fully contacted with the extractant for extraction, and the loaded organic phase and the raffinate are separated. Cyanex923 and LIX54 are mixed to form a composite extractant, and the volume ratio of Cyanex923 to LIX54 is controlled to be 2:1, sulfonated kerosene is used as a diluent, and the volume percentage of the composite extractant in the extraction system is 15%.

Through the extraction process, the separation of lithium ions and monovalent metal ions (mainly potassium) is achieved. The raffinate is directly returned to step S1 for water immersion. When the potassium ion concentration in the raffinate reaches the set value, the raffinate is deoiled and concentrated and evaporated to crystallize potassium sulfate; the evaporated water is returned to step S2-1 and used to add water to the filter residue A' and stir it into a slurry.

S5 adds carbonic acid to strip the loaded organic phase to obtain a lithium bicarbonate solution and a blank organic phase. During the stripping process, carbon dioxide and water are continuously introduced to form a gas-liquid-liquid three-phase stripping with the loaded 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 during stripping is controlled so that the lithium ion concentration in the lithium bicarbonate solution after stripping reaches about 8 g/L.

S6 removes the oil from the lithium bicarbonate solution and deeply removes calcium and magnesium, and pyrolyzes to obtain lithium carbonate slurry and carbon dioxide, and the carbon dioxide returns to step S5 for stripping (not shown in Figure 3). After the pyrolysis device has been running for a period of time, in order to clean the scale formed by lithium carbonate in the device, carbon dioxide is introduced into the device to convert lithium carbonate into soluble lithium bicarbonate, as shown by the dotted line in Figure 3. The lithium carbonate slurry is separated into lithium carbonate precipitate and mother liquor by solid-liquid separation. Since lithium carbonate is slightly soluble in water, the main component of the mother liquor is dissolved lithium carbonate. Part of the mother liquor returns to step S3 as an aqueous solution of carbonate, and part returns to step S5. Lithium carbonate reacts with carbon dioxide and water to form lithium bicarbonate, so that the lithium in the mother liquor can be fully recovered. The lithium carbonate precipitate is dried to obtain lithium carbonate solid, which is then crushed and packaged by air flow to form a lithium carbonate product, which meets the requirements of the industry standard "YS/T 582-2023 Battery Grade Lithium Carbonate".

Example 4

A method for preparing battery-grade lithium hydroxide, the process flow is shown in Figure 4, and includes the following steps.

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

S2-1 Calcium oxide is added to the leached slurry, the pH value of the leached slurry is adjusted to 7.0, and the filtrate A' and the filter residue A' are obtained by filtering. This step is mainly to neutralize the excess sulfuric acid in the leached slurry. In order to fully recover the small amount of lithium entrained in the filter residue A', the filter residue A' is added to water and stirred into a slurry, and the slurry is filtered to obtain residue and washing liquid, and the washing liquid is returned to step S1 for water leaching, and the residue is discharged.

S2-2 Add calcium oxide to the filtrate A', adjust the pH value to 13.0, filter after sufficient reaction, and obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide into the system, and removes iron ions, ferrous ions and most of magnesium ions. The main component of filtrate A is lithium hydroxide, and also includes soluble impurities formed after water immersion; the main component of filter residue A is calcium sulfate, and there may be excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A and use 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.

S3: Add sodium carbonate solution to filtrate A, filter after sufficient reaction, and obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, calcium sulfate dissolved in water is converted into calcium carbonate insoluble in water by adding sodium carbonate solution, and most of calcium ions are removed. Since the concentration of calcium ions formed by the dissolution of calcium sulfate is very low, little sodium carbonate needs to be added, and little sodium sulfate is generated. In order to fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water immersion. This operation can also make calcium carbonate play a role in neutralizing sulfuric acid.

S4 The filtrate B is deeply removed of calcium and magnesium by adsorption resin, and then fully contacted with the extractant for extraction, and then separated to obtain the loaded organic phase and the raffinate. TOPO and LIX860 are mixed to form a composite extractant, the volume ratio of TOPO to LIX860 is controlled to be 1:1, n-dodecane is used as the diluent, and the volume percentage of the composite extractant in the extraction system is 25%.

Through the extraction process, the separation of lithium ions and monovalent metal ions (sodium and potassium) is achieved. The raffinate is directly returned to step S1 for water immersion. When the concentration of monovalent metal ions in the raffinate reaches the set value after multiple cycles, the raffinate is deoiled and concentrated and evaporated by MVR to crystallize the solute (mainly sodium sulfate and potassium sulfate). The evaporated water is returned to step S2-1 and used to add water to the filter residue A' and stir it into slurry.

S5 adds sulfuric acid to strip the loaded organic phase to obtain a lithium sulfate 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 during stripping is controlled so that the lithium ion concentration in the lithium sulfate solution after stripping reaches more than 25 g/L.

S6 removes oil from the lithium sulfate solution and deeply removes calcium and magnesium, and performs bipolar membrane electrolysis to obtain lithium hydroxide solution and sulfuric acid. The sulfuric acid is returned to step S5 for stripping, and the lithium hydroxide solution is evaporated to obtain a lithium hydroxide product, which meets the requirements of the industry standard "YS/T 1568-2022 Battery Grade Anhydrous Lithium Hydroxide". The mother liquor obtained by evaporating the lithium hydroxide solution can be returned to step S3.

Example 5

A method for preparing battery-grade lithium chloride, the process flow is shown in Figure 5, and includes the following steps.

S1 After the waste lithium iron phosphate material is added with hydrogen peroxide and sulfuric acid for acidification reaction, it is leached in water to obtain the leaching slurry. The main active ingredient of the leaching slurry is lithium sulfate, and the lithium ion concentration is 1.0g/L.

S2-1 Calcium oxide is added to the leached slurry, the pH value of the leached slurry is adjusted to 6.5, and the filtrate A' and the filter residue A' are obtained by filtering. This step is mainly to neutralize the excess sulfuric acid in the leached slurry. In order to fully recover the small amount of lithium entrained in the filter residue A', the filter residue A' is added to water and stirred into a slurry, and the slurry is filtered to obtain residue and washing liquid, and the washing liquid is returned to step S1 for water leaching, and the residue is discharged.

S2-2 Add calcium oxide to the filtrate A', adjust the pH value to 13.5, filter after sufficient reaction, and obtain filtrate A and filter residue A. This step mainly converts lithium sulfate into lithium hydroxide, introduces hydroxide into the system, and removes iron ions, ferrous ions and most of magnesium ions. The main component of filtrate A is lithium hydroxide, and also includes soluble impurities formed after water immersion; the main component of filter residue A is calcium sulfate, and there may be excess calcium oxide or calcium hydroxide. In order to fully recover the small amount of lithium entrained in filter residue A and use 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.

S3: Add sodium carbonate solution to filtrate A, filter after sufficient reaction, and obtain filtrate B and filter residue B. Since calcium sulfate is slightly soluble in water, calcium sulfate dissolved in water is converted into calcium carbonate insoluble in water by adding sodium carbonate solution, and most of calcium ions are removed. Since the concentration of calcium ions formed by the dissolution of calcium sulfate is very low, little sodium carbonate needs to be added, and little sodium sulfate is generated. In order to fully recover the small amount of lithium entrained in filter residue B, filter residue B is returned to step S1 for water immersion. This operation can also make calcium carbonate play a role in neutralizing sulfuric acid.

S4 The filtrate B is deeply removed of calcium and magnesium by adsorption resin, and then fully contacted with the extractant for extraction, and the loaded organic phase and the raffinate are separated. TBP and LIX84 are mixed to form a composite extractant, and the volume ratio of TBP to LIX84 is controlled to be 0.2:1, sulfonated kerosene is used as a diluent, and the volume percentage of the composite extractant in the extraction system is 20%.

Through the extraction process, the separation of lithium ions and monovalent metal ions (sodium and potassium) is achieved. The raffinate is directly returned to step S1 for water immersion. When the concentration of monovalent metal ions in the raffinate reaches the set value after multiple cycles, the raffinate is deoiled and concentrated and evaporated by MVR to crystallize the solute. The evaporated water is returned to step S2 for adding water to the filter residue A' and stirring.

S5 adds hydrochloric acid to strip the loaded organic phase to obtain 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 during stripping is controlled so that the lithium ion concentration in the lithium chloride solution after stripping reaches 50 g/L or more.

S6 removes oil from the lithium chloride solution and deeply removes calcium and magnesium, and evaporates to obtain a lithium chloride product, which meets the requirements of the industry standard "YS/T744-2010 Battery Grade Anhydrous Lithium Chloride". The mother liquor obtained by evaporating the lithium chloride solution can be returned to step S3.

Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.

Claims (26)

1. A method for preparing a battery-grade lithium compound, characterized in that it comprises the following steps: S1. acidifying the lithium-containing raw material with sulfuric acid or roasting it with sulfate, and then leaching it with water to obtain a leaching slurry; the lithium-containing raw material is a lithium mineral or waste lithium battery material; S2: adding calcium oxide or calcium hydroxide to the leaching slurry, filtering after sufficient reaction to obtain filtrate A and filter residue A; S3: adding a substance for removing calcium ions to the filtrate A, filtering after sufficient reaction to obtain a filtrate B and a filter residue B; S4 fully contacting the filtrate B with the extractant for extraction, and then separating to obtain a loaded organic phase and a raffinate; S5 extracts the loaded 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 controls the amount of calcium oxide or calcium hydroxide added so that the pH value of filtrate A is 12.0-14.0. 3. The method according to claim 1, characterized in that step S2 is decomposed into two steps: S2-1 Adding an appropriate amount of calcium oxide or calcium hydroxide to the leaching slurry to neutralize the excess acid in the leaching slurry, filtering after the neutralization reaction is completed to obtain a filtrate A' and a filter residue A'; S2-2 Add calcium oxide or calcium hydroxide to the filtrate A', filter after sufficient reaction, and obtain filtrate A and filter residue A. 4. The method according to claim 3, characterized in that step S2-1 controls the amount of calcium oxide or calcium hydroxide added so that the pH value of the filtrate A' is 4.0 to 11.9, preferably 6.5 to 7.5. 5. The method according to claim 3, characterized in that, in step S2-2, the amount of calcium oxide or calcium hydroxide added is controlled so that the pH value of the filtrate A is 12.0-14.0. 6. The method according to claim 3 is characterized in that the filter residue A' is added with water and stirred into slurry, the slurry is filtered to obtain residue and washing liquid, and the residue is discharged; the washing liquid is used to wash the filter residue A, the washed filter residue A is discharged, and the washing liquid after washing is returned to step S1 for water immersion. 7. The method according to claim 1 or 3, characterized in that the substance for removing calcium ions 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. 8. The method according to claim 1 or 3, characterized in that the filter residue B obtained in step S3 is returned to step S1 for water immersion. 9. The method according to claim 1 or 3, characterized in that the extractant in step S4 is a composite extractant, comprising a neutral extractant and a chelating extractant, and the extraction system further comprises a diluent; the neutral extractant comprises one or a combination of tributyl phosphate, dimethylheptyl methyl phosphate, trioctylphosphine oxide, trioctyl/hexylphosphine oxide and N,N-di-(1-methylheptyl)acetamide, and the chelating extractant comprises one or a combination of 2-hydroxy-5-nonylacetophenone oxime, dodecylphenyl-methyl-β-diketone, and 2-hydroxy-5-nonylbenzaldehyde oxime. 10. The method according to claim 1 or 3, characterized in that the raffinate obtained in step S4 is returned to step S1 for water immersion to achieve recycling. 11. The method according to claim 10, characterized in that when the concentration of monovalent metal ions in the raffinate reaches a set value after multiple cycles, the raffinate is deoiled and concentrated and evaporated to allow the solute to crystallize out; the concentrated evaporation is preferably MVR evaporation. 12. The method according to claim 1 or 3, characterized in that the blank organic phase obtained in step S5 is returned to step S4 for extraction. 13. The method according to claim 1 or 3, characterized in that the lithium compound is lithium carbonate, step S5 adds carbonic acid to strip the loaded organic phase to obtain a lithium bicarbonate solution and a blank organic phase; step S6 removes oil from the lithium bicarbonate solution and deeply removes calcium and magnesium, pyrolyzes to obtain lithium carbonate slurry and carbon dioxide, separates the lithium carbonate slurry into solid and liquid to obtain a lithium carbonate precipitate and a mother liquor, and dries the lithium carbonate precipitate to obtain a battery-grade lithium carbonate product. 14. The method according to claim 13, characterized in that the stripping process in step S5 is to mix carbon dioxide and water to form a carbonate solution and then form a liquid-liquid two-phase extraction with the loaded organic phase, or to continuously introduce carbon dioxide and water into the loaded organic phase to form a gas-liquid-liquid three-phase extraction. 15. The method according to claim 13, characterized in that the carbon dioxide obtained in step S6 is returned to step S5 for stripping, and the mother liquor is returned to step S3 as a substance for removing calcium ions and/or returned to step S5. 16. The method according to claim 1 or 3, characterized in that the lithium compound is lithium carbonate, and step S5 is to strip the organic phase with a lithium bicarbonate solution to obtain lithium carbonate and a blank organic phase. 17. The method according to claim 16, characterized in that water and carbon dioxide are added to the obtained lithium carbonate to obtain a lithium bicarbonate solution after the reaction, the lithium bicarbonate solution is deoiled and deeply decalcified and magnesium is removed, and pyrolysis is performed to obtain a lithium carbonate slurry and carbon dioxide, the lithium carbonate slurry is solid-liquid separated to obtain a lithium carbonate precipitate and a mother liquor, and the lithium carbonate precipitate is dried to obtain a battery-grade lithium carbonate product. 18. The method according to claim 1 or 3, characterized in that the lithium compound is lithium hydroxide, step S5 adds sulfuric acid to strip the loaded organic phase to obtain a lithium sulfate solution and a blank organic phase; step S6 removes oil from the lithium sulfate solution and deeply removes calcium and magnesium, performs bipolar membrane electrolysis to obtain a lithium hydroxide solution and sulfuric acid, and evaporates the lithium hydroxide solution to obtain a battery-grade lithium hydroxide product. 19. The method according to claim 18, characterized in that the sulfuric acid obtained in step S6 is returned to step S5 for stripping. 20. The method according to claim 1 or 3, characterized in that the lithium compound is lithium hydroxide, and step S5 adds hydrochloric acid to strip the loaded organic phase to obtain a lithium chloride solution and a blank organic phase; step S6 removes oil from the lithium chloride solution and deeply removes calcium and magnesium, performs bipolar membrane electrolysis to obtain a lithium hydroxide solution and hydrochloric acid, and evaporates the lithium hydroxide solution to obtain a battery-grade lithium hydroxide product. 21. The method according to claim 20, characterized in that the hydrochloric acid obtained in step S6 is returned to step S5 for stripping. 22. The method according to claim 1 or 3, characterized in that the lithium compound is lithium chloride, and step S5 adds hydrochloric acid to strip the loaded organic phase to obtain a lithium chloride solution and a blank organic phase; step S6 removes oil from the lithium chloride solution and deeply removes calcium and magnesium, and evaporates to obtain a battery-grade lithium chloride product. 23. The method according to claim 1 or 3, characterized in that in step S4, before extraction, the filtrate B is deeply decalcified and magnesium removed. 24. The method according to claim 1 or 3, characterized in that the lithium ion concentration in the leaching slurry in step S1 is 0.5-4 g/L. 25. The method according to claim 1 or 3, characterized in that, in step S1, the lithium-containing raw material 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 immersion to achieve recycling, and when the potassium ion concentration in the raffinate reaches a set value after multiple cycles, the raffinate is deoiled and then concentrated and evaporated to crystallize the solute to obtain a potassium sulfate product. 26. The method according to claim 13 or 17 or 18 or 20 or 22 or 23, characterized in that the deep removal of calcium and magnesium is performed by adsorbing calcium and magnesium with an adsorption resin.