Method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate

Abstract

The application relates to the technical field of lithium batteries, in particular to a method for recycling lithium phosphate battery waste to produce battery-grade lithium carbonate, which provides lithium phosphate waste, adds the lithium phosphate waste powder into a lithium sulfate solution, stirs to obtain slurry, adds acid liquor, an additive and an oxidizing agent into the slurry to perform oxidation leaching, once filters the obtained leaching liquor, adds an alkaline adjusting agent into the obtained once-filtered liquor, performs secondary filtration, adds sodium carbonate into the secondary-filtered liquor, performs tertiary filtration, dries the obtained solid, adds water, performs carbonization reaction and twice purification, and finally obtains the end product; the lithium carbonate produced by the method has a purity of 99.8%, the lithium recovery rate reaches more than 98%, the lithium element in the lithium phosphate battery waste is recycled and utilized, the lithium phosphate battery waste is converted into lithium carbonate used for lithium ion battery materials, and the method has remarkable significance for relieving the lack of lithium resources and realizing green and low-carbon transformation.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate. Background Technology

[0002] Currently, the vast majority of new energy vehicles use lithium iron phosphate batteries as their power source. The theoretical lifespan of lithium iron phosphate batteries is only 7-8 years. Such a large-scale consumption generates a huge number of waste lithium batteries, which will accumulate in large quantities. If they are not effectively disposed of, they will cause huge environmental pollution and waste of resources.

[0003] Currently, the recycling processes for waste lithium iron phosphate batteries can be divided into pyrometallurgical recycling and hydrometallurgical recycling. Pyrometallurgical recycling involves disassembling and crushing the batteries, followed by high-temperature incineration. This transforms the metallic elements in the electrode materials into stable metal oxides, which are then separated and recovered. This process is short and produces no wastewater, but it has an unfriendly operating environment and high energy consumption, and is currently only in the laboratory research stage. Hydrometallurgical recycling primarily uses acid leaching to enrich metallic lithium, combined with various impurity removal processes to recover lithium elements. This method has a high recovery rate and good separation properties, but the purity of the resulting product is relatively low. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate.

[0005] The technical solution adopted is as follows:

[0006] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0007] Lithium iron phosphate waste is provided. The waste lithium iron phosphate powder is added to a lithium sulfate solution and stirred to obtain a slurry. Then, acid, additives, and oxidants are added to the slurry for oxidative leaching. The resulting leachate is filtered once. An alkaline regulator is added to the first filtrate for a second filtration. Sodium carbonate is added to the second filtrate for a third filtration. The resulting solid is dried, pulverized, added to water, and subjected to pressurized and sealed heating reaction with carbon dioxide. After filtration, a purification agent is added to the filtrate for a first purification reaction. After filtration, the filtrate is passed through an adsorption column filled with ion exchange resin for a second purification. The purified liquid obtained after the second purification is pyrolyzed. The lithium carbonate obtained from the pyrolysis is washed with boiling pure water and dried to obtain the final product.

[0008] Furthermore, the acid solution is any one or more of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, preferably phosphoric acid.

[0009] Furthermore, the additives include anionic surfactants and tributyl phosphate, wherein the weight ratio of the anionic surfactants to tributyl phosphate is 1-5:1-5.

[0010] Furthermore, the oxidant is air, oxygen, or ozone.

[0011] Furthermore, the alkalinity regulator is any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, calcium carbonate, and magnesium carbonate, preferably sodium hydroxide.

[0012] Furthermore, the pH of the first filtrate after adding an alkaline regulator is 3.5-4.5.

[0013] Furthermore, the impurity remover is lithium oxalate or oxalic acid.

[0014] Furthermore, the ion exchange resin is modified by amination.

[0015] Furthermore, the amination modification method of the ion exchange resin is as follows:

[0016] The sulfonic acid-based ion exchange resin is washed sequentially with water, soaked in NaOH solution, washed with water until neutral, soaked in dilute hydrochloric acid solution, and washed with water until neutral again. This process is repeated 3-5 times until dry. The resin is then swollen in ethanol, pyridine is added, and the mixture is stirred for 6-12 hours. After filtration, the resin is washed with acetone and dried. It is then swollen in dichloroethane, thionyl chloride is added, and the mixture is refluxed for 5-10 hours. After filtration, the resin is washed with acetone and dried. It is then swollen in dichloroethane, amination reagent is added, and the mixture is refluxed for 24-48 hours. After filtration, the resin is washed with acetone, soaked in water for 24-48 hours, and then dried.

[0017] Furthermore, the amination reagent is ethylenediamine, diethylenetriamine, or triethylenetetramine.

[0018] The beneficial effects of this invention are:

[0019] This invention provides a method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate. Anionic surfactants and tributyl phosphate are used as additives to disrupt the aggregation state of lithium, increase the dissolution and diffusion rate of lithium ions, and improve the lithium leaching rate. Carbon dioxide is used to decompose and convert the slightly soluble lithium carbonate into easily soluble lithium bicarbonate, while most impurities do not participate in the reaction, thus achieving the separation of lithium from most insoluble impurities. During the carbonation process, some Ca... 2+ Mg 2+ and Li +Together, they transform into soluble bicarbonate and enter the carbonation solution. During pyrolysis, they transform into magnesium carbonate and calcium carbonate precipitates, which enter the lithium carbonate, causing a decline in lithium carbonate quality. Secondary purification using ion exchange resin adsorption columns can effectively remove impurity ions and improve the purity of lithium carbonate. After amination modification, sulfonic acid-based ion exchange resins can more effectively and quickly capture and adsorb divalent metal ions such as Ca. 2+ Mg 2+ By improving adsorption performance, the lithium carbonate recovered and produced by the method of this invention has a purity of 99.8%, and the lithium recovery rate in lithium iron phosphate battery waste reaches more than 98%. This realizes the recycling and utilization of lithium elements in lithium iron phosphate battery waste, converting them into lithium carbonate for lithium-ion battery materials. This is of great significance for alleviating the shortage of lithium resources and realizing green and low-carbon transformation. Attached Figure Description

[0020] Figure 1 This is a photograph of the lithium carbonate prepared in Example 1 of the present invention. Detailed Implementation

[0021] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0022] Example 1:

[0023] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0024] 2.5 kg of lithium iron phosphate waste (lithium content 2.5 wt%) was added to 12.5 L of lithium sulfate solution with a concentration of 5 g / L. The mixture was stirred at 80 rpm for 30 min to obtain a slurry. Then, 750 mL of phosphoric acid solution with a concentration of 1.8 mol / L, 25 g of sodium dodecylbenzenesulfonate, and 100 g of tributyl phosphate were added to the slurry, and oxygen was introduced at a flow rate of 2.5 L / min for oxidative leaching. After stirring for 2 h, the resulting leachate was filtered once. Sodium hydroxide was added to the first filtrate to adjust the pH to 3.5. A second filtration was then performed, and sodium carbonate was added to the second filtrate to adjust the pH. The mixture was filtered three more times. The resulting solid was dried, pulverized, and added to a high-pressure reactor. 25 times its weight of water was added, and carbon dioxide was introduced to pressurize the reactor to 0.25 MPa. The reactor was then sealed and heated to 55°C for 2 hours. After filtration, oxalic acid was added to the filtrate to bring the pH of the system to 4. The mixture was then heated to 50°C and stirred for 2 hours for the first purification. After the reaction was completed, the mixture was filtered again. The resulting filtrate was passed through an adsorption column filled with ion exchange resin at a rate of 10 ± 0.5 mL / min for the second purification. The purified solution obtained after the second purification was heated to 75°C and pyrolyzed at 500 r / min for 6 hours. The lithium carbonate obtained from the pyrolysis was filtered out, washed with boiling pure water, and dried to obtain the final product.

[0025] The ion exchange resin undergoes amination modification, the specific method of which is as follows:

[0026] 600g of C100E type sulfonic acid ion exchange resin was washed with water, soaked in 0.1mol / L NaOH solution for 4h, washed with water until neutral, soaked in 0.1mol / L dilute hydrochloric acid solution for 4h, washed with water until neutral again, and the above operation was repeated 5 times. After drying, it was added to ethanol to swell for 24h, then 1L of pyridine was added and stirred for 10h, filtered, washed with acetone and dried, added to dichloroethane to swell for 12h, then 1L of sulfoxide was added, heated to reflux and reacted for 10h, filtered, washed with acetone and dried, added to dichloroethane to swell for 12h, then 60g of ethylenediamine was added, heated to reflux and reacted for 24-48h, filtered, washed with acetone, and then soaked in water for 24h and dried.

[0027] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.7%, and the purity of lithium carbonate is ≥99.8%.

[0028] Example 2:

[0029] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0030] 2.5 kg of lithium iron phosphate waste (lithium content 2.5 wt%) was added to 12.5 L of lithium sulfate solution with a concentration of 5 g / L. The mixture was stirred at 80 rpm for 30 min to obtain a slurry. Then, 750 mL of phosphoric acid solution with a concentration of 1.8 mol / L, 25 g of sodium dodecylbenzenesulfonate, and 25 g of tributyl phosphate were added to the slurry, and oxygen was introduced at a flow rate of 2.5 L / min for oxidative leaching. After stirring for 2 h, the resulting leachate was filtered once. Sodium hydroxide was added to the first filtrate to adjust the pH to 4.5. A second filtration was then performed, and sodium carbonate was added to the second filtrate to adjust the pH. The mixture was filtered three more times. The resulting solid was dried, pulverized, and added to a high-pressure reactor. 25 times its weight of water was added, and carbon dioxide was introduced to pressurize the reactor to 0.25 MPa. The reactor was then sealed and heated to 55°C for 2 hours. After filtration, oxalic acid was added to the filtrate to bring the pH of the system to 5. The mixture was then heated to 50°C and stirred for 2 hours for the first purification. After the reaction was completed, the mixture was filtered again. The resulting filtrate was passed through an adsorption column filled with ion exchange resin at a rate of 10 ± 0.5 mL / min for the second purification. The purified solution obtained after the second purification was heated to 75°C and pyrolyzed at 500 r / min for 6 hours. The lithium carbonate obtained from the pyrolysis was filtered out, washed with boiling pure water, and dried to obtain the final product.

[0031] The ion exchange resin was modified by amination, and the specific method was the same as in Example 1.

[0032] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.4%, and the purity of lithium carbonate is ≥99.8%.

[0033] Example 3:

[0034] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0035] 2.5 kg of lithium iron phosphate waste (lithium content 2.5 wt%) was added to 12.5 L of lithium sulfate solution with a concentration of 5 g / L. The mixture was stirred at 80 rpm for 30 min to obtain a slurry. Then, 750 mL of phosphoric acid solution with a concentration of 1.8 mol / L, 25 g of sodium dodecylbenzenesulfonate, and 50 g of tributyl phosphate were added to the slurry, and oxygen was introduced at a flow rate of 2.5 L / min for oxidative leaching. After stirring for 2 h, the leachate was filtered once. Sodium hydroxide was added to the first filtrate to adjust the pH to 3.5. A second filtration was then performed, and sodium carbonate was added to the second filtrate to adjust the pH. 9. After three more filtrations, the resulting solid is dried, pulverized, and added to a high-pressure reactor. 25 times its weight of water is added, carbon dioxide is introduced, the pressure is increased to 0.25 MPa, the reactor is sealed, and heated to 55°C for 2 hours. After filtration, oxalic acid is added to the filtrate to bring the pH of the system to 4. The temperature is raised to 50°C and stirred for 2 hours for the first purification. After the reaction is completed, the filtrate is filtered again. The resulting filtrate is passed through an adsorption column filled with ion exchange resin at a rate of 10 ± 0.5 mL / min for the second purification. The purified solution obtained after the second purification is heated to 75°C and pyrolyzed at 500 r / min for 6 hours. The lithium carbonate obtained from the pyrolysis is filtered out, washed with boiling pure water, and dried to obtain the final product.

[0036] The ion exchange resin was modified by amination, and the specific method was the same as in Example 1.

[0037] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.0%, and the purity of lithium carbonate is ≥99.8%.

[0038] Example 4:

[0039] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0040] 2.5 kg of lithium iron phosphate waste (lithium content 2.5 wt%) was added to 12.5 L of lithium sulfate solution with a concentration of 5 g / L. The mixture was stirred at 80 rpm for 30 min to obtain a slurry. Then, 750 mL of phosphoric acid solution with a concentration of 1.8 mol / L, 50 g of sodium dodecylbenzenesulfonate, and 25 g of tributyl phosphate were added to the slurry, and oxygen was introduced at a flow rate of 2.5 L / min for oxidative leaching. After stirring for 2 h, the resulting leachate was filtered once. Sodium hydroxide was added to the first filtrate to adjust the pH to 4.5. A second filtration was then performed, and sodium carbonate was added to the second filtrate to adjust the pH. 9. After three more filtrations, the resulting solid is dried, pulverized, and added to a high-pressure reactor. 25 times its weight of water is added, carbon dioxide is introduced, and the reactor is pressurized to 0.25 MPa. The reactor is then sealed and heated to 55°C for 2 hours. After filtration, oxalic acid is added to the filtrate to bring the pH of the system to 5. The temperature is raised to 50°C and stirred for 2 hours for the first purification. After the reaction is complete, the reactor is filtered again. The resulting filtrate is passed through an adsorption column filled with ion exchange resin at a rate of 10 ± 0.5 mL / min for the second purification. The purified solution obtained after the second purification is heated to 75°C and pyrolyzed at 500 r / min for 6 hours. The lithium carbonate obtained from the pyrolysis is filtered out, washed with boiling pure water, and dried to obtain the final product.

[0041] The ion exchange resin was modified by amination, and the specific method was the same as in Example 1.

[0042] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.2%, and the purity of lithium carbonate is ≥99.8%.

[0043] Example 5:

[0044] A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate:

[0045] 2.5 kg of lithium iron phosphate waste (lithium content 2.5 wt%) was added to 12.5 L of lithium sulfate solution with a concentration of 5 g / L. The mixture was stirred at 80 rpm for 30 min to obtain a slurry. Then, 750 mL of phosphoric acid solution with a concentration of 1.8 mol / L, 25 g of sodium dodecylbenzenesulfonate, and 50 g of tributyl phosphate were added to the slurry, and oxygen was introduced at a flow rate of 2.5 L / min for oxidative leaching. After stirring for 2 h, the leachate was filtered once. Sodium hydroxide was added to the first filtrate to adjust the pH to 3.5. A second filtration was then performed, and sodium carbonate was added to the second filtrate to adjust the pH. The mixture was filtered three more times. The resulting solid was dried, pulverized, and added to a high-pressure reactor. 25 times its weight of water was added, and carbon dioxide was introduced to pressurize the reactor to 0.25 MPa. The reactor was then sealed and heated to 55°C for 2 hours. After filtration, oxalic acid was added to the filtrate to bring the pH of the system to 4. The mixture was then heated to 50°C and stirred for 2 hours for the first purification. After the reaction was completed, the mixture was filtered again. The resulting filtrate was passed through an adsorption column filled with ion exchange resin at a rate of 10 ± 0.5 mL / min for the second purification. The purified solution obtained after the second purification was heated to 75°C and pyrolyzed at 500 r / min for 6 hours. The lithium carbonate obtained from the pyrolysis was filtered out, washed with boiling pure water, and dried to obtain the final product.

[0046] The ion exchange resin was modified by amination, and the specific method was the same as in Example 1.

[0047] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.1%, and the purity of lithium carbonate is ≥99.8%.

[0048] Comparative Example 1:

[0049] It is basically the same as Example 1, except that sodium dodecylbenzenesulfonate is not added.

[0050] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 97.4%, and the purity of lithium carbonate is ≥99.8%.

[0051] Comparative Example 2:

[0052] It is basically the same as Example 1, except that tributyl phosphate is not added.

[0053] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 96.9%, and the purity of lithium carbonate is ≥99.8%.

[0054] Comparative Example 3:

[0055] It is basically the same as Example 1, except that it does not undergo secondary purification through an ion exchange resin adsorption column.

[0056] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 99.2%, and the purity of lithium carbonate is 97.8%.

[0057] Comparative Example 4:

[0058] It is basically the same as Example 1, except that the ion exchange resin is not modified by amination.

[0059] Calculations show that the lithium recovery rate in lithium iron phosphate battery waste is 98.6%, and the purity of lithium carbonate is 99.2%.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate, characterized in that, The process involves providing lithium iron phosphate waste, adding the waste lithium iron phosphate powder to a lithium sulfate solution, stirring to obtain a slurry, then adding acid, additives, and oxidizing agents to the slurry for oxidative leaching, filtering the resulting leachate once, adding an alkaline regulator to the first filtrate for a second filtration, adding sodium carbonate to the second filtrate for a third filtration, drying the resulting solid, pulverizing it, adding it to water, pressing and heating it with carbon dioxide, filtering it, adding a purification agent to the filtrate for a first purification reaction, filtering it again, passing the resulting filtrate through an adsorption column filled with ion exchange resin for a second purification, pyrolyzing the purified liquid, washing the lithium carbonate obtained from the pyrolysis with boiling pure water, and drying it to obtain the final product. The additives include anionic surfactants and tributyl phosphate, wherein the weight ratio of the anionic surfactants to tributyl phosphate is 1-5:1-5. The ion exchange resin has been modified by amination; The amination modification method of the ion exchange resin is as follows: The sulfonic acid ion exchange resin is washed sequentially with water, soaked in NaOH solution, washed with water until neutral, soaked in dilute hydrochloric acid solution, and washed with water until neutral again. This process is repeated 3-5 times until dry. The resin is then swollen in ethanol, pyridine is added, and the mixture is stirred for 6-12 hours. After filtration, the resin is washed with acetone and dried. It is then swollen in dichloroethane, thionyl chloride is added, and the mixture is refluxed for 5-10 hours. After filtration, the resin is washed with acetone and dried. It is then swollen in dichloroethane, amination reagent is added, and the mixture is refluxed for 24-48 hours. After filtration, the resin is washed with acetone, and then soaked in water for 24-48 hours before drying. The amination reagent is ethylenediamine, diethylenetriamine, or triethylenetetramine.

2. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, The acid solution is any one or more of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid.

3. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 2, characterized in that, The acid solution is phosphoric acid.

4. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, The oxidant is air, oxygen, or ozone.

5. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, The alkalinity regulator is any one or more of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, calcium carbonate, and magnesium carbonate.

6. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, The alkalinity regulator is sodium hydroxide.

7. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, After adding an alkaline regulator, the pH of the first filtrate is 3.5-4.

5.

8. The method for recycling lithium iron phosphate battery waste to produce battery-grade lithium carbonate as described in claim 1, characterized in that, The impurity removal agent is lithium oxalate or oxalic acid.

Images