A method of extracting lithium

Abstract

The application belongs to the field of lithium ion batteries, and specifically discloses a method for extracting lithium. In the method, lithium is selectively extracted and enriched from a lithium-rich solution by using a lithium ion battery cathode material, and the method has the characteristics of simple operation, high lithium extraction efficiency, green environmental protection, large treatment capacity of the lithium-rich solution and small energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and specifically relates to a method for extracting lithium. Background Technology

[0002] With the increasing application of lithium batteries in transportation, medical, and technological fields, their market share will continue to grow. Lithium, as the most crucial metallic raw material in lithium batteries, plays a vital role in the development of new energy. Currently, global lithium resources are mainly concentrated in lepidolite, spodumene, and salt lakes. However, non-renewable lithium resources such as lepidolite and spodumene are becoming increasingly scarce. Therefore, extracting lithium from salt lakes and other lithium-rich resources has become a hot topic for researchers and companies.

[0003] Because lithium batteries have a limited lifespan, they are gradually phased out and retired due to performance degradation as their service life increases. These discarded lithium-ion batteries not only bring enormous environmental pressure but also offer a broad prospect for the recycling of valuable metal resources. Therefore, adopting effective recycling measures and policies to recover lithium can reduce dependence on primary mineral resources and contribute to achieving global carbon neutrality goals and environmental protection, highlighting its economic value and environmental benefits. Furthermore, it helps to better stimulate consumer spending, promote automobile consumption, and cultivate and expand the power battery recycling industry, achieving a win-win situation for both economic and social benefits. Therefore, the recycling of lithium-ion batteries has become a focus of attention for enterprises.

[0004] Among them, retired and scrapped lithium-ion batteries are numerous, and lithium extraction from them has become the most popular method besides lithium extraction from lithium ore and salt lakes. Lithium extraction from waste batteries still requires transferring lithium from the waste battery powder into a solution using wet methods. Methods for extracting lithium from lithium-rich solutions such as salt lakes or wet leaching solutions of recycled battery powder mainly include adsorption, extraction, and electrochemical methods. For example, Chinese patents CN1702043A and CN103121724A both report on the preparation of ion sieves with selective adsorption properties for lithium ion adsorption and extraction, which can be applied to lithium-rich solution environments such as brine to achieve selective lithium extraction. However, the aforementioned ion sieves have disadvantages during use, including large material dissolution losses (solubility loss), small processing capacity of lithium-rich solutions, and relatively small selective adsorption capacity of lithium. In addition, some patent documents propose extraction methods to remove lithium from brine. For example, Chinese patents CN105502551A and CN111945017A use organophosphorus extractants to extract lithium from wastewater. However, the above-mentioned methods require the use of other co-extractants and organic solvents to achieve significant results. Furthermore, pretreatment of the application environment is necessary, leading to limitations in applicability, poor universality, and high overall costs. Based on these issues, some experts have innovatively proposed electrochemical lithium extraction methods. For instance, patents CN107201452A and CN102382984A utilize the special properties of electrode materials and apply external current to the electrodes. Combined with charge transfer characteristics, this allows for the directional movement of lithium ions in the solution, achieving selective extraction. Although these technologies can extract lithium, they still face challenges such as high investment in electrolytic and auxiliary equipment and materials, low processing efficiency, and operational difficulties.

[0005] In summary, there is still an urgent need to develop a process for extracting lithium from lithium-rich solutions that is efficient, simple, and relatively low-cost. Summary of the Invention

[0006] In view of the problems of low efficiency, complex operation and high cost of lithium extraction from lithium-rich solutions in the existing technology, the present invention will provide a method for extracting lithium.

[0007] To achieve the above objectives, the following technical solutions are specifically included:

[0008] A method for extracting lithium includes the following steps:

[0009] (1) The positive electrode material of lithium-ion battery is mixed with a solvent in sequence, ball milled and dried to obtain the positive electrode material;

[0010] (2) The positive electrode material, oxidant and water are sequentially mixed, delithiated, and separated into solid and liquid to obtain delithiated liquid and delithiated residue;

[0011] (3) The delithiation liquid is reacted with a carbonate solution to undergo a precipitation reaction, followed by solid-liquid separation and washing to obtain lithium carbonate;

[0012] (4) The lithium-delithiation residue, lithium-rich solution, reducing agent, alkali and water are sequentially mixed, subjected to lithium extraction reaction and solid-liquid separation to obtain lithium-extraction liquid and lithium-extraction residue.

[0013] In the lithium extraction method of this invention, an oxidant is first used to oxidize and delithigate the lithium-ion battery cathode material, obtaining a delithiated residue with selective adsorption. Then, a reducing agent is used to reduce and intercalate lithium in the lithium-rich solution within the delithiated residue, achieving selective extraction and enrichment of lithium in the lithium-rich solution, thereby achieving the goal of simple and efficient extraction and utilization of lithium resources. The lithium extraction method of this invention is characterized by its simplicity, efficiency, environmental friendliness, large capacity for processing lithium-rich solutions, and low energy consumption.

[0014] In one embodiment, in step (1), the lithium-ion battery cathode material includes lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), and lithium manganese iron phosphate (LiFe2O4). 0.5 Mn 0.5 PO4), lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (LiNi) x Co y Mn z O2, x = 0.5-0.8, y = 0.1-0.2, z = 0.1-0.3, preferably x, y, z are at least one of 0.5, 0.2, 0.3 respectively.

[0015] In the method of the present invention, the lithium-ion battery cathode material can be a new cathode material or a material obtained by recycling cathode materials from waste batteries.

[0016] In one embodiment, in step (1), the solvent includes ethanol.

[0017] In one embodiment, in step (1), the mass ratio of the lithium-ion battery cathode material to the solvent is 1 (1:5).

[0018] In one embodiment, in step (1), the ball milling speed is 100-300 rpm and the ball milling time is 120-300 min.

[0019] In one embodiment, in step (1), the drying temperature is 80-100°C.

[0020] In one embodiment, in step (2), the oxidant includes at least one of sodium persulfate, hydrogen peroxide, chlorine, and ozone.

[0021] The aforementioned oxidant can cause lithium to be extracted from the cathode material, making it a delithiation residue. This delithiation residue has selective adsorption properties, which facilitates the adsorption and insertion of lithium ions in subsequent lithium-rich solutions, thereby achieving selective extraction and enrichment of lithium in lithium-rich solutions.

[0022] In one embodiment, in step (2), the temperature of the delithiation reaction is 40-90°C, preferably 60-90°C, and the time of the delithiation reaction is 60-180 min, preferably 120-180 min, and more preferably 150-180 min.

[0023] In one embodiment, in step (2), the amount of the oxidant is 0.8-2 times the amount of lithium in the cathode material, more preferably 0.8-1.5 times, and more preferably 0.9-1.1 times.

[0024] The amount of oxidant is related to the delithiation efficiency of the cathode material. Under the above-mentioned amount of oxidant, the present invention has a high delithiation efficiency.

[0025] In one embodiment, the specific process of mixing in step (2) is as follows: the positive electrode material and a portion of water are mixed to obtain a pre-delithiation solution; the oxidant is mixed with the remaining water to obtain an oxidant solution; the oxidant solution and the pre-delithiation solution are then mixed; the pH value of the pre-delithiation solution is 4-9, and the mass ratio of the positive electrode material to water in the pre-delithiation solution is 1:(3-5); the volume of the oxidant solution is 3%-5% of the volume of the pre-delithiation solution.

[0026] At the pH value of the pre-delithiation solution mentioned above, it is more conducive to improving the delithiation effect.

[0027] In one embodiment, in step (2), a catalyst is added during the delithiation reaction. The catalyst includes at least one of copper chloride, cobalt chloride, and ferric chloride, and the concentration of metal ions in the catalyst is 0.5-1.0 g / L.

[0028] In one embodiment, in step (3), the delithiation liquid is further concentrated to obtain a lithium precipitation pre-liquid, wherein the lithium concentration in the lithium precipitation pre-liquid is 8-15 g / L.

[0029] The concentrated delithiation solution can improve the efficiency and purity of lithium carbonate precipitation and shorten the precipitation cycle.

[0030] In one embodiment, in step (3), the carbonate concentration in the carbonate solution is 35-60 g / L.

[0031] In one embodiment, in step (3), the carbonate in the carbonate solution includes at least one of sodium carbonate and potassium carbonate.

[0032] In one embodiment, in step (3), the temperature of the precipitation reaction is 80-100°C and the time of the precipitation reaction is 30-120 min.

[0033] In one embodiment, in step (3), the lithium carbonate is further purified. The purification process includes the following steps: carbon dioxide is introduced into the lithium carbonate at a flow rate of 100-500 mL / min for 0.5-2.5 h at 60-80 °C, followed by filtration, washing, and drying.

[0034] The lithium carbonate product and its precursor can be reprocessed into cathode materials through processes such as sintering to achieve the purpose of recycling.

[0035] In one embodiment, in step (4), the reducing agent includes at least one of sodium sulfite, sodium sulfide, hydrogen sulfide, sulfur dioxide, and sodium metabisulfite.

[0036] Using the aforementioned reducing agent, the delithiation residue with selective adsorption can be reduced and lithium-intercalated in a lithium-rich solution, so that lithium in the lithium-rich solution is adsorbed and enriched in the delithiation residue, and finally enriched in the form of lithium extraction residue.

[0037] In one embodiment, in step (4), the amount of the residue after delithiation is 1-3 times the amount of lithium in the lithium-rich solution.

[0038] The amount of residue after delithiation is related to the efficiency of lithium extraction. Under the above-mentioned amount of residue, the goal of efficient lithium extraction can be achieved.

[0039] In one embodiment, in step (4), the amount of the reducing agent is 0.9-1.5 times the amount of lithium in the lithium-rich solution.

[0040] In one embodiment, in step (4), the amount of the alkali is 0.9-1.5 times the amount of lithium in the lithium-rich solution.

[0041] In one embodiment, in step (4), the lithium concentration in the lithium-rich solution is 0.1-1.0 g / L.

[0042] In one embodiment, in step (4), the alkali includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia water.

[0043] In one embodiment, in step (4), the temperature of the lithium extraction reaction is 20-90°C, preferably 50-80°C, and the reaction time is 30-180 min.

[0044] In one embodiment, in step (4), the mixing specifically involves: mixing the lithium-rich solution and the delithiation residue to obtain a pre-lithiation liquid; mixing the reducing agent, alkali, and water to obtain a reducing agent solution; and then mixing the pre-lithiation liquid and the reducing agent solution; the pH value of the pre-lithiation liquid is 4-10, more preferably 5-9, and even more preferably 5-8; and the volume percentage of the reducing agent solution is 3%-5% based on the total volume of the reducing agent solution and the pre-lithiation liquid being 100%.

[0045] In one embodiment, in step (4), the lithium extraction residue can be recycled, and the recycling includes the following recycling steps:

[0046] (5-1) The lithium extraction residue, oxidant and water are sequentially mixed, delithiated, and separated into solid and liquid to obtain delithiated liquid and delithiated residue;

[0047] (5-2) The delithiation liquid is reacted with a carbonate solution to undergo a precipitation reaction. After solid-liquid separation and washing, lithium carbonate is obtained.

[0048] (5-3) The lithium-delithiation residue, lithium-rich solution, reducing agent, alkali and water are sequentially mixed, lithium extraction reaction is performed and solid-liquid separation is performed to obtain lithium-extraction liquid and lithium-extraction residue;

[0049] (5-4) Repeat steps (5-1) to (5-3) in a loop.

[0050] In step (4) of this invention, the lithium extraction residue replaces the cathode material in step (2) for the delithiation reaction, and the lithium precipitation and lithium extraction processes in steps (3) and (4) are carried out to achieve the recycling of the delithiation residue.

[0051] Referring to the lithium extraction rate obtained in step (4), the lithium extraction performance of the lithium extraction residue is examined based on the lithium extraction rate. The lithium extraction rate in step (4) is taken as the original lithium extraction performance of the lithium extraction residue. After the lithium extraction residue has been circulated multiple times, when the lithium extraction performance of the lithium extraction residue is less than 50% of the original lithium extraction performance, the recycling of the lithium extraction residue for lithium extraction is stopped, and the lithium extraction residue is treated by wet recycling. Wet recycling generally includes acid leaching, impurity removal, and other processes. Finally, a solution containing metal ions can be obtained. After further impurity removal and batching, it can be directly used as a nickel cobalt manganese sulfate or iron phosphate solution to synthesize nickel cobalt manganese ternary precursor materials or iron phosphate (FePO4) and other materials to achieve recycling.

[0052] The concentration of lithium in the post-lithiation solution is detected. If the lithium concentration is <0.05 g / L, it can be reused after water treatment to remove impurities and reduce COD. If the lithium concentration in the post-lithiation solution is ≥0.05 g / L, it can be used as a lithium-rich solution for lithium extraction to avoid lithium loss.

[0053] In one embodiment, in step (4), the lithium-rich solution includes at least one of salt lake brine, battery powder wet leaching solution, and lithium-containing wastewater.

[0054] In one embodiment, in step (4), the lithium-rich solution is further subjected to filtration and adsorption for oil removal.

[0055] In one embodiment, in step (4), a catalyst is added during the lithium extraction reaction. The catalyst includes at least one of cobalt chloride and manganese chloride. In the solution system of the lithium extraction reaction, the concentration of metal ions in the catalyst is 0.5-1.0 g / L.

[0056] In the delithiation and lithium extraction reactions of this invention, a catalyst can be added to provide a certain degree of catalytic effect on the reaction.

[0057] Compared with existing technologies, this invention has the following advantages: This invention utilizes lithium-ion battery cathode materials to selectively extract and enrich lithium from lithium-rich solutions, achieving a simple and efficient extraction and utilization of lithium resources. The lithium extraction method of this invention is characterized by simple operation, high lithium extraction efficiency, environmental friendliness, large capacity for processing lithium-rich solutions, and low energy consumption. Attached Figure Description

[0058] Figure 1 A schematic flowchart of the lithium extraction method of the present invention. Detailed Implementation

[0059] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0060] The lithium manganese oxide battery powder used below was purchased from Guangxi Lijin New Materials Co., Ltd., model LJM-05; the lithium-rich solution used below is the leachate from the wet recycling treatment of lithium-containing waste or brine from a salt lake, and its main components are ions of Li, Na, K, Ca, Mg, B, and Si, as well as Cl. - SO4 2- The lithium-rich solution used in the following examples and comparative examples is the same lithium-rich solution, wherein the content of Li is 0.1-1.0 g / L, the content of Na is 50-120 g / L, and the contents of K, Ca and Mg are 3-15 g / L.

[0061] Example 1

[0062] A method for extracting lithium, the flowchart of which is attached. Figure 1 It includes the following steps:

[0063] (1) 100g of lithium manganese oxide battery powder (Li content of 3.84%) was mixed with anhydrous ethanol at a solid-liquid ratio of 1:3, and then ball-milled in a planetary ball mill at a speed of 200rpm for 120min. The mixture was then dried in an oven at 90℃ to obtain the positive electrode material.

[0064] (2) The positive electrode material and pure water are mixed in a reactor at a ratio of 1g positive electrode material to 4mL water to obtain a pre-delithiation solution, and the pH value of the pre-delithiation solution is adjusted to 7.

[0065] Sodium persulfate was dissolved in pure water at 4% of the volume of the liquid before delithiation to obtain a sodium persulfate solution.

[0066] Sodium persulfate solution was pumped into the reactor at a rate of 2.0 mL / min. The delithiation reaction was carried out for 180 min with continuous stirring and at 90 °C. When the reaction was completed, the pH of the delithiated solution was measured to be 2.6. The solution was then filtered and washed to obtain the delithiated solution and the delithiated residue. The delithiation reaction involved the following delithiation reaction: 2LiMn2O4 + Na2S2O8 = 4MnO2 + Li2SO4 + Na2SO4.

[0067] Based on the amount of lithium in the cathode material, the amount of sodium persulfate is 1 times the amount of lithium in the cathode material.

[0068] The lithium content in the delithiation liquid and delithiation residue was detected. The lithium content before and after delithiation was calculated, and the delithiation rate reached 99%, with the dissolution loss of the cathode material <0.5%.

[0069] (3) The delithiation liquid is concentrated and impurities are removed to obtain a lithium precipitation liquid with a lithium element concentration of 10 g / L.

[0070] The lithium pre-precipitation solution was reacted with a sodium carbonate solution with a carbonate concentration of 40 g / L at 90 °C for 60 min. After solid-liquid separation and water washing, lithium carbonate precipitate was obtained.

[0071] Then, carbon dioxide was introduced into the lithium carbonate precipitate at 70℃ and a flow rate of 200 mL / min for 1.5 h. After that, the precipitate was filtered, washed with water, and dried to obtain the lithium carbonate product with a purity of 99.0%.

[0072] This lithium carbonate product and its precursor can be reprocessed into cathode materials through processes such as sintering to achieve the purpose of recycling.

[0073] (4) Take a lithium-rich solution with a lithium element concentration of 0.5 g / L into the reactor, and filter the lithium-rich solution through a sand core filter to remove impurities and suspended matter in the solution. Then, the lithium-rich solution is degreased by activated carbon adsorption. Finally, the pH value of the lithium-rich solution is adjusted to approximately 4.5-9 using liquid alkali.

[0074] Then add the delithiation residue obtained in step (2) in an amount twice the amount of lithium in the lithium-rich solution, and adjust the pH of the solution to 8 to obtain the pre-lithiation solution.

[0075] Sodium sulfite, sodium hydroxide, and water are mixed to obtain a reducing agent solution. The volume ratio of the reducing agent solution is 4%, based on the total volume of the reducing agent solution and the pre-lithiation solution being 100%. The amount of sodium sulfite and sodium hydroxide is 1 times the amount of lithium in the lithium-rich solution.

[0076] The lithium extraction solution was heated at 50℃, and the reducing agent solution was pumped into the lithium extraction solution in the reactor at a rate of 3.0 mL / min. The reaction was carried out continuously with stirring at 50℃ for 90 min. After the reaction was completed, the solution was filtered and washed with water to obtain the lithium extraction solution and lithium extraction residue. The lithium extraction reaction involves the following lithium intercalation reaction: 4MnO2+Li2SO4+Na2SO3+2NaOH=2LiMn2O4+2Na2SO4+H2O;

[0077] The lithium content in the lithium extraction liquid and lithium extraction residue was tested. The lithium extraction rate was 97% and the dissolution loss of the lithium extraction residue was <0.6% after lithium extraction.

[0078] (5) Detect the lithium concentration in the lithium extraction solution. If the lithium concentration is <0.05g / L, it can be reused after water treatment to remove impurities, reduce COD, wash and filter. If the lithium concentration in the lithium extraction solution is ≥0.05g / L, the lithium extraction solution can be used as a lithium-rich solution for lithium extraction to avoid lithium loss.

[0079] (6) Refer to the process in step (2), replace the positive electrode material with the lithium extraction residue obtained in step (4), and carry out a new delithiation reaction with the oxidant, and carry out the lithium precipitation reaction in step (3) and the lithium extraction reaction in step (4) as one cycle of the lithium extraction residue. The lithium extraction residue is cycled multiple times (generally ≥50 times).

[0080] Referring to the lithium extraction rate obtained in step (4), the lithium extraction performance of the lithium extraction residue is examined by the lithium extraction rate. The lithium extraction rate (97%) in the current step (4) is taken as the original lithium extraction performance of the lithium extraction residue in this embodiment. After the lithium extraction residue is circulated multiple times, when the lithium extraction performance of the lithium extraction residue is less than 50% of the original lithium extraction performance, the recycling of the lithium extraction residue for lithium extraction is stopped, and the lithium extraction residue is treated by wet recycling.

[0081] Wet recycling generally includes processes such as acid leaching and impurity removal, ultimately yielding a solution containing metal ions. After further impurity removal and batching, this solution can be directly used as a nickel cobalt manganese sulfate or iron phosphate solution to synthesize nickel cobalt manganese ternary precursor materials or iron phosphate (FePO4) and other materials, thus achieving recycling.

[0082] Example 2

[0083] A method for extracting lithium includes the following steps:

[0084] (1) 100g of lithium manganese oxide powder (Li content of 3.84%) was mixed with anhydrous ethanol at a solid-liquid ratio of 1:3, and then ball-milled in a planetary ball mill at a speed of 200rpm for 120min. The mixture was then dried in an oven at 90℃ to obtain the positive electrode material.

[0085] (2) The positive electrode material and water are mixed in a reactor at a ratio of 1g of positive electrode material to 4mL of water to obtain a pre-delithiation solution, and the pH value of the pre-delithiation solution is adjusted to 6.

[0086] Sodium persulfate and pure water were mixed and dissolved at 4% of the volume of the lithium removal solution to obtain a sodium persulfate solution.

[0087] Sodium persulfate solution was pumped into the reactor at a rate of 2.0 mL / min. The delithiation reaction was carried out for 180 min under continuous stirring and at 80 °C. At the end of the reaction, the pH of the delithiated solution was measured to be 2.75. The solution was then filtered and washed to obtain the delithiated solution and the delithiated residue. The delithiation reaction involved the following delithiation reaction: 2LiMn2O4 + Na2S2O8 = 4MnO2 + Li2SO4 + Na2SO4.

[0088] Based on the amount of lithium in the cathode material, the amount of sodium persulfate is 0.9 times the amount of lithium in the cathode material.

[0089] The lithium content in the delithiation liquid and delithiation residue was detected. The lithium content before and after delithiation was calculated, and the delithiation rate reached 85%, with the dissolution loss of the cathode material <0.4%.

[0090] (3) The delithiation liquid is concentrated and impurities are removed to obtain a lithium precipitation liquid with a lithium element concentration of 10 g / L.

[0091] The lithium pre-precipitation solution was reacted with a sodium carbonate solution with a carbonate concentration of 40 g / L at 90 °C for 60 min. After solid-liquid separation and water washing, lithium carbonate precipitate was obtained.

[0092] Then, carbon dioxide was introduced into the lithium carbonate precipitate at 70℃ and a flow rate of 200 mL / min for 1.5 h. After that, the precipitate was filtered, washed with water, and dried to obtain the lithium carbonate product with a purity of 99.0%.

[0093] This lithium carbonate product and its precursor can be reprocessed into cathode materials through processes such as sintering to achieve the purpose of recycling.

[0094] (4) Take a lithium-rich solution with a lithium element concentration of 0.5 g / L into the reactor, and filter the lithium-rich solution through a sand core filter to remove impurities and suspended matter in the solution. Then, the lithium-rich solution is degreased by activated carbon adsorption. Finally, the pH value of the lithium-rich solution is adjusted to approximately 4.5-9 using liquid alkali.

[0095] Then add the delithiation residue obtained in step (2) in an amount twice the amount of lithium in the lithium-rich solution, and adjust the pH of the solution to 8 to obtain the pre-lithiation solution.

[0096] Sodium sulfite, sodium hydroxide, and water are mixed to obtain a reducing agent solution. The volume ratio of the reducing agent solution is 4%, based on the total volume of the reducing agent solution and the pre-lithiation solution being 100%. The amount of sodium sulfite and sodium hydroxide is 1 times the amount of lithium in the lithium-rich solution.

[0097] The pre-lithiation solution was heated at 50℃, and the mixture was pumped into the pre-lithiation solution in the reactor at a rate of 3.0 mL / min. The reaction was carried out under continuous stirring and at 50℃ for 90 min. After the reaction was completed, the solution was filtered and washed with water to obtain the post-lithiation solution and post-lithiation residue. The lithium extraction reaction involves the following lithium intercalation reaction: 4MnO2+Li2SO4+Na2SO3+2NaOH=2LiMn2O4+2Na2SO4+H2O;

[0098] The lithium content in the lithium extraction liquid and lithium extraction residue was tested. The lithium extraction rate was 90% and the dissolution loss of the lithium extraction residue was <0.5% based on the lithium content before and after lithium extraction.

[0099] (5) Detect the lithium concentration in the lithium extraction solution. If the lithium concentration is <0.05g / L, it can be reused after water treatment to remove impurities, reduce COD, wash and filter. If the lithium concentration in the lithium extraction solution is ≥0.05g / L, the lithium extraction solution can be used as a lithium-rich solution for lithium extraction to avoid lithium loss.

[0100] (6) Refer to the process of step (2), replace the positive electrode material with the lithium extraction residue obtained in step (4), and carry out a new delithiation reaction with the oxidant, and carry out the lithium precipitation reaction in step (3) and the lithium extraction reaction in step (4) as one cycle of the lithium extraction residue, and the lithium extraction residue is cycled multiple times.

[0101] Referring to the lithium extraction rate obtained in step (4), the lithium extraction performance of the lithium extraction residue is examined by the lithium extraction rate. The lithium extraction rate (90%) in the current step (4) is taken as the original lithium extraction performance of the lithium extraction residue in this embodiment. After the lithium extraction residue is circulated multiple times, when the lithium extraction performance of the lithium extraction residue is less than 50% of the original lithium extraction performance, the recycling of the lithium extraction residue for lithium extraction is stopped, and the lithium extraction residue is treated by wet recycling.

[0102] Wet recycling generally includes processes such as acid leaching and impurity removal, ultimately yielding a solution containing metal ions. After further impurity removal and batching, this solution can be directly used as a nickel cobalt manganese sulfate or iron phosphate solution to synthesize nickel cobalt manganese ternary precursor materials or iron phosphate (FePO4) and other materials, thus achieving recycling.

[0103] Example 3

[0104] A method for extracting lithium includes the following steps:

[0105] (1) 100g of lithium manganese oxide powder (Li content of 3.84%) was mixed with anhydrous ethanol at a solid-liquid ratio of 1:3, and then ball-milled in a planetary ball mill at a speed of 200rpm for 120min. The mixture was then dried in an oven at 90℃ to obtain the positive electrode material.

[0106] (2) The positive electrode material and pure water are mixed in a reactor at a ratio of 1g positive electrode material to 4mL water to obtain a pre-delithiation solution, and the pH value of the pre-delithiation solution is adjusted to 6.

[0107] Sodium persulfate and pure water were mixed and dissolved at 4% of the volume of the lithium removal solution to obtain a sodium persulfate solution.

[0108] Sodium persulfate solution was pumped into the reactor at a rate of 2.0 mL / min. The delithiation reaction was carried out for 150 min with continuous stirring and at 80 °C. At the end of the reaction, the pH of the delithiated solution was measured to be 2.45. The solution was then filtered and washed to obtain the delithiated solution and the delithiated residue. The delithiation reaction involved the following delithiation reaction: 2LiMn2O4 + Na2S2O8 = 4MnO2 + Li2SO4 + Na2SO4.

[0109] Based on the amount of lithium in the cathode material, the amount of sodium persulfate is 1.1 times the amount of lithium in the cathode material.

[0110] The lithium content in the delithiation liquid and delithiation residue was detected. The lithium content before and after delithiation was calculated, and the delithiation rate reached 93%, with a cathode material dissolution loss of <0.4%.

[0111] (3) The delithiation liquid is concentrated and impurities are removed to obtain a lithium precipitation liquid with a lithium element concentration of 10 g / L.

[0112] The lithium pre-precipitation solution was reacted with a sodium carbonate solution with a carbonate concentration of 40 g / L at 90 °C for 60 min. After solid-liquid separation and water washing, lithium carbonate precipitate was obtained.

[0113] Then, carbon dioxide was introduced into the lithium carbonate precipitate at 70℃ and a flow rate of 200 mL / min for 1.5 h. After that, the precipitate was filtered, washed with water, and dried to obtain the lithium carbonate product with a purity of 99.2%.

[0114] This lithium carbonate product and its precursor can be reprocessed into cathode materials through processes such as sintering to achieve the purpose of recycling.

[0115] (4) Take a lithium-rich solution with a lithium element concentration of 0.5 g / L into the reactor, and filter the lithium-rich solution through a sand core filter to remove impurities and suspended matter in the solution. Then, the lithium-rich solution is degreased by activated carbon adsorption. Finally, the pH value of the lithium-rich solution is adjusted to approximately 4.5-9 using liquid alkali.

[0116] Then add the delithiation residue obtained in step (2) in an amount twice the amount of lithium in the lithium-rich solution, and adjust the pH of the solution to 8 to obtain the pre-lithiation solution.

[0117] Sodium sulfite, sodium hydroxide, and water are mixed to obtain a reducing agent solution. The volume ratio of the reducing agent solution is 4%, based on the total volume of the reducing agent solution and the pre-lithiation solution being 100%. The amount of sodium hydroxide is 1 times the amount of lithium in the lithium-rich solution, and the amount of sodium sulfite is 1.1 times the amount of lithium in the lithium-rich solution.

[0118] The pre-lithiation solution was heated at 50℃, and the mixture was pumped into the pre-lithiation solution in the reactor at a rate of 3.0 mL / min. The mixture was stirred continuously and the lithium extraction reaction was carried out at 40℃ for 90 min. After the reaction was completed, the solution was filtered and washed with water to obtain the post-lithiation solution and post-lithiation residue. The lithium extraction reaction involves the following lithium intercalation reaction: 4MnO2+Li2SO4+Na2SO3+2NaOH=2LiMn2O4+2Na2SO4+H2O;

[0119] The lithium content in the lithium extraction liquid and lithium extraction residue was tested. The lithium extraction rate was 96% and the dissolution loss of the lithium extraction residue was <0.5% after lithium extraction.

[0120] (5) Detect the lithium concentration in the lithium extraction solution. If the lithium concentration is <0.05g / L, it can be reused after water treatment to remove impurities, reduce COD, wash and filter. If the lithium concentration in the lithium extraction solution is ≥0.05g / L, the lithium extraction solution can be used as a lithium-rich solution for lithium extraction to avoid lithium loss.

[0121] (6) Refer to the process in step (2), replace the positive electrode material with the lithium extraction residue obtained in step (4), and carry out a new delithiation reaction with the oxidant, and carry out the lithium precipitation reaction in step (3) and the lithium extraction reaction in step (4) as one cycle of the lithium extraction residue. The lithium extraction residue is cycled multiple times (generally ≥50 times).

[0122] Referring to the lithium extraction rate obtained in step (4), the lithium extraction performance of the lithium extraction residue is examined by the lithium extraction rate. The lithium extraction rate (96%) in the current step (4) is taken as the original lithium extraction performance of the lithium extraction residue in this embodiment. After the lithium extraction residue is circulated multiple times, when the lithium extraction performance of the lithium extraction residue is less than 50% of the original lithium extraction performance, the recycling of the lithium extraction residue for lithium extraction is stopped, and the lithium extraction residue is treated by wet recycling.

[0123] Wet recycling generally includes processes such as acid leaching and impurity removal, ultimately yielding a solution containing metal ions. After further impurity removal and batching, this solution can be directly used as a nickel cobalt manganese sulfate or iron phosphate solution to synthesize nickel cobalt manganese ternary precursor materials or iron phosphate (FePO4) and other materials, thus achieving recycling.

[0124] Example 4

[0125] The difference between this embodiment and embodiment 1 is that the temperature of the delithiation reaction in step (2) of this embodiment is 80°C, while the other steps are the same.

[0126] Example 5

[0127] The difference between this embodiment and embodiment 1 is that the temperature of the delithiation reaction in step (2) of this embodiment is 40°C, while the other steps are the same.

[0128] Example 6

[0129] The difference between this embodiment and embodiment 1 is that the amount of sodium persulfate in step (2) of this embodiment is 0.8 times the amount of lithium in the positive electrode material, and the other steps are the same.

[0130] Example 7

[0131] The difference between this embodiment and embodiment 1 is that the amount of sodium persulfate in step (2) of this embodiment is twice the amount of lithium in the cathode material, and the other steps are the same.

[0132] Example 8

[0133] The difference between this embodiment and embodiment 1 is that the amount of sodium sulfite (Na2SO3) in step (4) of this embodiment is 0.9 times the amount of lithium in the lithium-rich solution, and the other steps are the same.

[0134] Example 9

[0135] The difference between this embodiment and embodiment 1 is that the amount of sodium sulfite in step (4) of this embodiment is 1.5 times the amount of lithium in the lithium-rich solution, and the other steps are the same.

[0136] Example 10

[0137] The difference between this embodiment and embodiment 1 is that the temperature of the lithium extraction reaction in step (4) of this embodiment is 20°C, while the other steps are the same.

[0138] Example 11

[0139] The difference between this embodiment and embodiment 1 is that the temperature of the lithium extraction reaction in step (4) of this embodiment is 90°C, while the other steps are the same.

[0140] Example 12

[0141] The difference between this embodiment and embodiment 1 is that cobalt chloride was added in step (2) of the delithiation reaction and step (4) of the lithium extraction reaction in this embodiment. After adding zirconium chloride, the concentration of the catalyst in the reaction system, based on its cobalt element concentration, is 0.8 g / L. The other steps are the same.

[0142] Example 13

[0143] The difference between this embodiment and embodiment 1 is that in this embodiment, 100g of lithium iron phosphate powder is used instead of 100g of lithium manganese oxide powder in step (1), and the other steps are the same.

[0144] In this embodiment, the delithiation reaction in step (2) involves the following lithium insertion / extraction reaction: 2LiFePO4+Na2S2O8=2FePO4+Li2SO4+Na2SO4; the lithium extraction reaction in step (4) involves the following lithium insertion / extraction reaction: 2FePO4+Li2SO4+Na2SO3+2NaOH=2LiFePO4+2Na2SO4+H2O.

[0145] Example 14

[0146] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the pH value of the pre-lithiation solution is 4, and the other steps are the same.

[0147] Example 15

[0148] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the pH value of the pre-lithiation solution is 9, and the other steps are the same.

[0149] Example 16

[0150] The difference between this embodiment and embodiment 1 is that in step (4) of this embodiment, the amount of the residue after delithiation is 1.0 times the amount of lithium in the lithium-rich solution, and the other steps are the same.

[0151] Example 17

[0152] The difference between this embodiment and embodiment 1 is that in step (4) of this embodiment, the amount of the residue after delithiation is 3.0 times the amount of lithium in the lithium-rich solution, and the other steps are the same.

[0153] Example 18

[0154] The difference between this embodiment and embodiment 1 is that in step (4) of this embodiment, the pH value of the lithium extraction solution is 4, and the other steps are the same.

[0155] Example 19

[0156] The difference between this embodiment and embodiment 1 is that in step (4) of this embodiment, the pH value of the lithium extraction solution is 10, and the other steps are the same.

[0157] Comparative Example 1

[0158] The difference between this comparative example and Example 1 is that no delithiation reaction was performed in this comparative example, as detailed below:

[0159] (1) 100g of lithium manganese oxide powder (Li content of 3.84%) was mixed with anhydrous ethanol at a solid-liquid ratio of 1:3, and then ball-milled in a planetary ball mill at a speed of 200rpm for 120min. The mixture was then dried in an oven at 90℃ to obtain the positive electrode material.

[0160] (2) Take a lithium-rich solution with a lithium element concentration of 0.5 g / L into the reactor, and filter the lithium-rich solution through a sand core filter to remove impurities and suspended matter in the solution. Then, the lithium-rich solution is subjected to activated carbon adsorption to remove oil. Finally, the pH value of the lithium-rich solution is adjusted to approximately 4.5-9 using liquid alkali.

[0161] Then add the positive electrode material obtained in step (1) in an amount twice the amount of lithium element in the lithium-rich solution, and adjust the pH value to 8 to obtain the lithium extraction solution.

[0162] Sodium sulfite, sodium hydroxide, and water are mixed to obtain a reducing agent solution. The volume ratio of the reducing agent solution is 4%, based on the total volume of the reducing agent solution and the pre-lithiation solution being 100%. The amount of sodium sulfite and sodium hydroxide is 1 times the amount of lithium in the lithium-rich solution.

[0163] The pre-lithiation solution was heated at 50°C, and the mixture was pumped into the pre-lithiation solution in the reactor at a rate of 3.0 mL / min. The mixture was stirred continuously and the lithium extraction reaction was carried out at 50°C for 90 min. After the reaction was completed, the solution was filtered and washed with water to obtain the post-lithiation solution and post-lithiation residue.

[0164] The lithium element involved in this paper was measured by ICP and atomic absorption spectroscopy. The test results of steps (2) to (4) are shown in Table 1. C1, C2 and C3 in Table 1 are explained as follows: C1 is the multiple of the amount of sodium persulfate to the amount of lithium element in the positive electrode material, i.e., C1 = [n(Na2S2O8) / n(positive electrode material Li)]; C2 is the multiple of the amount of sodium sulfite to the amount of lithium element in the lithium-rich solution, i.e., C2 = [n(Na2SO3) / n(lithium-rich solution Li)]; C3 is the multiple of the amount of residue after delithiation to the amount of lithium element in the lithium-rich solution, i.e., C3 = [n(delithiation residue) / n(lithium-rich solution Li)].

[0165] Table 1

[0166]

[0167]

[0168]

[0169] The lithium content in the lithium extraction liquid and lithium extraction residue was detected. Based on the lithium content before and after lithium extraction, the lithium extraction rate of the material in Comparative Example 1 without delithiation by oxidant was 2.5%, and the dissolution loss of the delithiation residue was <0.5%. By comparing Comparative Example 1 and Example 1, it can be proved that the cathode material without delithiation cannot be lithium extracted.

[0170] In the lithium extraction method of the present invention, an oxidant is first used to oxidize and delithiate the lithium battery cathode material to obtain a delithiated residue with selective adsorption. Then, a reducing agent is used to reduce and intercalate lithium in the lithium-rich solution in the delithiated residue, thereby achieving selective extraction and enrichment of lithium in the lithium-rich solution, and thus achieving the purpose of simple and efficient extraction and utilization of lithium resources.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for extracting lithium, characterized in that, Includes the following steps: (1) The positive electrode material of lithium-ion battery is mixed with a solvent in sequence, ball-milled and dried to obtain the positive electrode material; (2) The positive electrode material, oxidant and water are sequentially mixed, delithiated, and separated into solid and liquid to obtain delithiated liquid and delithiated residue; (3) The delithiation liquid is reacted with a carbonate solution to undergo a precipitation reaction, followed by solid-liquid separation and washing to obtain lithium carbonate; (4) The lithium-free residue, lithium-rich solution, reducing agent, alkali and water are sequentially mixed, subjected to lithium extraction reaction and solid-liquid separation to obtain lithium-extraction liquid and lithium-extraction residue; In step (4), the lithium extraction residue can be recycled, and the recycling includes the following recycling steps: (5-1) The lithium extraction residue, oxidant and water are sequentially mixed, subjected to delithiation reaction and solid-liquid separation to obtain delithiation liquid and delithiation residue; (5-2) The delithiation liquid is reacted with a carbonate solution to undergo a precipitation reaction. After solid-liquid separation and washing, lithium carbonate is obtained. (5-3) The lithium-free residue, lithium-rich solution, reducing agent, alkali and water are sequentially mixed, subjected to lithium extraction reaction and solid-liquid separation to obtain lithium-extraction liquid and lithium-extraction residue; (5-4) Repeat steps (5-1) to (5-3) in a loop.

2. The method for extracting lithium as described in claim 1, characterized in that, In step (1), the lithium-ion battery cathode material includes at least one of lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide.

3. The method for extracting lithium as described in claim 1, characterized in that, In step (2), the temperature of the delithiation reaction is 40-90℃ and the time of the delithiation reaction is 60-180min.

4. The method for extracting lithium as described in claim 1, characterized in that, In step (2), the amount of the oxidant is 0.8-2 times the amount of lithium in the cathode material.

5. The method for extracting lithium as described in claim 1, characterized in that, In step (2), the specific mixing process is as follows: the positive electrode material and a portion of water are mixed to obtain a pre-delithiation solution; the oxidant is mixed with the remaining water to obtain an oxidant solution; the oxidant solution and the pre-delithiation solution are then mixed; the pH value of the pre-delithiation solution is 4-9, and the mass ratio of the positive electrode material to water in the pre-delithiation solution is 1:(3-5); the volume of the oxidant solution is 3%-5% of the volume of the pre-delithiation solution.

6. The method for extracting lithium as described in claim 1, characterized in that, Includes at least one of the following: In step (2), a catalyst is added during the delithiation reaction. The catalyst includes at least one of copper chloride, cobalt chloride, and ferric chloride. In the solution system of the delithiation reaction, the concentration of metal ions in the catalyst is 0.5-1.0 g / L. In step (4), a catalyst is added during the lithium extraction reaction. The catalyst includes at least one of cobalt chloride and manganese chloride. In the solution system of the lithium extraction reaction, the concentration of metal ions in the catalyst is 0.5-1.0 g / L.

7. The method for extracting lithium as described in claim 1, characterized in that, In step (4), the amount of the residue after delithiation is 1-3 times the amount of lithium in the lithium-rich solution.

8. The method for extracting lithium as described in claim 1, characterized in that, In step (4), the temperature of the lithium extraction reaction is 20-90℃.

9. The method for extracting lithium as described in claim 1, characterized in that, In step (4), the mixing specifically involves: mixing the lithium-rich solution and the delithiation residue to obtain a pre-lithiation liquid; mixing the reducing agent, alkali, and water to obtain a reducing agent solution; and then mixing the pre-lithiation liquid and the reducing agent solution; the pH value of the pre-lithiation liquid is 4-10; and the volume percentage of the reducing agent solution is 3%-5% based on the total volume of the reducing agent solution and the pre-lithiation liquid being 100%.

10. The method for extracting lithium as described in claim 1, characterized in that, Includes at least one of the following: In step (1), the solvent includes ethanol; In step (1), the mass ratio of the lithium-ion battery cathode material to the solvent is 1 (1:5). In step (1), the rotation speed of the ball mill is 100-300 rpm, and the ball milling time is 120-300 min; In step (2), the oxidant includes at least one of sodium persulfate, hydrogen peroxide, chlorine, and ozone; In step (3), the delithiation liquid is further concentrated to obtain the pre-lithiation liquid, and the concentration of lithium in the pre-lithiation liquid is 8-15 g / L. In step (3), the carbonate concentration in the carbonate solution is 35-60 g / L, and the carbonate in the carbonate solution includes at least one of sodium carbonate and potassium carbonate. In step (3), the temperature of the precipitation reaction is 80-100℃, and the time of the precipitation reaction is 30-120 min; In step (3), the lithium carbonate is further purified. The purification process includes the following steps: carbon dioxide is introduced into the lithium carbonate at a flow rate of 100-500 mL / min for 0.5-2.5 h at 60-80 °C, followed by filtration, washing, and drying. In step (4), the reducing agent includes at least one of sodium sulfite, sodium sulfide, hydrogen sulfide, sulfur dioxide, and sodium metabisulfite; In step (4), the amount of the reducing agent is 0.9-1.5 times the amount of lithium in the lithium-rich solution; In step (4), the amount of the alkali is 0.9-1.5 times the amount of lithium in the lithium-rich solution; In step (4), the lithium concentration in the lithium-rich solution is 0.1-1.0 g / L.

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