Method for Recovering Lithium from Lithium Batteries

Abstract

The present application discloses a method for recovering lithium from lithium batteries. The method for recovering lithium from lithium batteries comprises the following steps: obtaining the mixed powder of the positive and negative electrodes of the lithium battery to be recovered; performing low-acid leaching on the mixed powder of the positive and negative electrodes to obtain a low-acid leaching solution and a low-acid leaching residue; adding iron powder to the low-acid leaching solution to obtain a solution after copper removal and a copper metal product; performing oxidation treatment on the solution after copper removal to obtain an oxidized solid product and a first filtrate; performing pulping and neutralization precipitation on the oxidized solid product to obtain an iron-aluminum slag and a first lithium-containing solution; recovering a lithium carbonate product from the first lithium-containing solution. The present application solves the technical problem of the low recovery rate of recovering lithium from lithium batteries in the prior art.

Description

Technical Field

[0001] This application relates to the technical field of recycling of waste lithium - ion batteries, and particularly to a method for recovering lithium from lithium batteries. Background Art

[0002] With the rapid development of the new - energy vehicle industry, China has become the world's largest producer and seller of new - energy vehicles. The production and sales volume of power batteries have also been increasing year by year, and the recycling and utilization of power batteries are extremely urgent. China is the world's largest producer of lithium - ion batteries, and the lithium - ion battery industry has become one of the high - tech industries strongly supported by the state. However, the treatment of waste products and production waste materials in the lithium - ion battery industry has become a difficult problem that needs to be solved urgently for the clean production of the lithium - ion battery industry. Waste lithium - ion batteries belong to typical solid wastes. Their resource utilization can not only solve the environmental problems caused by waste lithium - ion batteries, but also alleviate the shortage of strategic metal resources in China and promote the sustainable development of China's battery industry.

[0003] Currently, the main method for recycling the cathode materials of waste lithium - ion batteries is the hydrometallurgical process of sulfuric acid leaching. However, in the sulfuric acid leaching method, lithium is leached synchronously with metals such as aluminum, copper, iron, nickel, cobalt, and manganese. After the separation and recovery process of metals such as nickel, cobalt, and manganese, the enrichment and recovery of lithium can be carried out. However, during the separation and recovery process of metals such as nickel, cobalt, and manganese, a part of lithium is lost, resulting in a low recovery rate of lithium recovery. Summary of the Invention

[0004] The main purpose of this application is to provide a method for recovering lithium from lithium batteries, aiming to solve the technical problem of the low recovery rate of lithium recovery from lithium batteries in the existing technology.

[0005] To achieve the above purpose, this application provides a method for recovering lithium from lithium batteries. The method for recovering lithium from lithium batteries includes the following steps:

[0006] Obtain the mixed powder of the positive and negative electrodes of the lithium battery to be recycled;

[0007] Perform low - acid leaching on the mixed powder of the positive and negative electrodes to obtain a low - acid leaching solution and low - acid leaching residue;

[0008] Add iron powder to the low - acid leaching solution to obtain a solution after copper removal and copper metal products;

[0009] Perform oxidation treatment on the solution after copper removal to obtain oxidation solid products and a first filtrate;

[0010] Perform pulping and neutralization precipitation on the oxidation solid products to obtain iron - aluminum slag and a first lithium - containing solution;

[0011] Recover lithium carbonate products from the first lithium - containing solution.

[0012] Optionally, the step of subjecting the positive and negative electrode mixed powder to low-acid leaching to obtain a low-acid leaching solution and a low-acid leaching residue includes:

[0013] Adding a first sulfuric acid solution and a reducing agent to the positive and negative electrode mixed powder, so that the positive and negative electrode mixed powder is leached for 3-10 hours under the condition of a pH value of 1.5-2.5 to obtain a low-acid leaching solution and a low-acid leaching residue.

[0014] Optionally, the reducing agent includes sulfur dioxide and / or hydrogen peroxide, and the addition amount of the reducing agent is 1.2-2.5 times the total molar amount of cobalt and manganese in the positive and negative electrode mixed powder.

[0015] Optionally, the oxidized solid product includes jarosite, and the step of subjecting the solution after copper removal to oxidation treatment to obtain an oxidized solid product and a first filtrate includes:

[0016] Adjust the pH value of the solution after copper removal to 1.5-2.0, adjust the temperature to 80-95 °C, add hydrogen peroxide for oxidation treatment, and carry out oxidation treatment for 3-8 hours to obtain jarosite and a first filtrate.

[0017] Optionally, the step of slurrying and neutralizing and precipitating the oxidized solid product to obtain an iron-aluminum slag and a first lithium-containing solution includes:

[0018] Slurry the oxidized solid product, and adjust the pH value to 0.5-1.0, adjust the temperature to 80-90 °C to obtain a high-iron hot solution;

[0019] Add the high-iron hot solution and a neutralizing agent to a precipitation tank for neutralizing precipitation, control the reaction temperature of the neutralizing precipitation to be 75-85 °C, the reaction pH value to be 2.0-3.8, and control the concentration of ferric iron in the mixed solution in the precipitation tank to be less than or equal to 1 g / L to obtain an iron-aluminum slag and a first lithium-containing solution.

[0020] Optionally, the reaction temperature of the neutralizing precipitation is 85-85 °C, and the reaction pH value is 2.5-3.5.

[0021] Optionally, the neutralizing agent includes sodium carbonate and / or nickel carbonate.

[0022] Optionally, after the step of subjecting the positive and negative electrode mixed powder to low-acid leaching to obtain a low-acid leaching solution and a low-acid leaching residue, it further includes:

[0023] Add a second sulfuric acid solution with a concentration of 250-300 g / L to the low-acid leaching residue, carry out high-acid leaching for 3-5 hours, then add a reducing agent, and continue leaching for 1-3 hours to obtain a graphite slag and a high-acid leaching solution;

[0024] After adjusting the pH value of the high-acid leaching solution, it is returned to the low-acid leaching process for low-acid leaching of the positive and negative mixed powder.

[0025] Optionally, the step of recovering lithium carbonate product from the first lithium-containing solution includes:

[0026] Adjust the pH value of the first lithium-containing solution to 9.5 - 10.5 to obtain a first filter residue and a second lithium-containing solution;

[0027] Add a sodium carbonate solution to the second lithium-containing solution, and after solid-liquid separation, obtain a lithium carbonate product.

[0028] Optionally, after the step of oxidizing the post-copper-removal solution to obtain an oxidized solid product and a first filtrate, the following steps are further included:

[0029] Adjust the pH value of the first filtrate to 3.5 - 4.5 to obtain a second filter residue and a second filtrate;

[0030] Return the second filter residue to the low-acid leaching process for low-acid leaching together with the positive and negative mixed powder.

[0031] The present application provides a method for recovering lithium from lithium batteries. By obtaining the positive and negative mixed powder of the lithium battery to be recycled and performing low-acid leaching on the positive and negative mixed powder to obtain a low-acid leaching solution and a low-acid leaching residue, the leaching of lithium and metals such as nickel, cobalt, and manganese is realized. Then, by adding iron powder to the low-acid leaching solution, a post-copper-removal solution and a copper metal product are obtained, realizing the replacement of iron and copper. Then, by oxidizing the post-copper-removal solution to obtain an oxidized solid product and a first filtrate, the separation of lithium and metals such as nickel, cobalt, and manganese is realized. Then, by slurrying and neutralizing and precipitating the oxidized solid product, an iron-aluminum slag and a first lithium-containing solution are obtained, realizing the separation of iron and lithium. Then, by recovering the lithium carbonate product from the first lithium-containing solution, the recovery of lithium in the lithium battery is realized. Compared with the method of recovering lithium by sulfuric acid leaching, after lithium and metals such as aluminum, copper, iron, nickel, cobalt, and manganese are simultaneously leached in the present application, by making lithium form an oxidized solid product with iron and precipitate out of the solution, the separation of lithium and metals such as nickel, cobalt, and manganese is realized, effectively avoiding the loss of lithium in the separation and recovery process of metals such as nickel, cobalt, and manganese, improving the recovery rate of lithium recovered from lithium batteries, and overcoming the technical problem of the low recovery rate of lithium recovered from lithium batteries in the prior art. Description of the Drawings

[0032] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0033] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic flow chart of an embodiment of the method for recovering lithium from lithium batteries in the present application;

[0035] Figure 2 It is a schematic flow chart of an implementable manner of the method for recovering lithium from lithium batteries in the present application.

[0036] The realization of the purpose, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0037] To make the above objects, features and advantages of the present invention more obvious and understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] With the rapid development of the new energy vehicle industry, China has become the world's largest producer and seller of new energy vehicles. The production and sales volume of power batteries have also been increasing year by year, and the recycling and utilization of power batteries are imminent. China is the world's largest producer of lithium-ion batteries. The lithium-ion battery industry has become one of the high-tech industries strongly supported by the state. However, the treatment of waste products and production waste materials in the lithium-ion battery industry has become a difficult problem that needs to be solved urgently for the clean production of the lithium-ion battery industry. Waste lithium-ion batteries belong to typical solid waste. Their resource utilization can not only solve the environmental problems caused by waste lithium-ion batteries, but also alleviate the shortage of strategic metal resources in China and promote the sustainable development of China's battery industry.

[0039] At present, the main method for recycling the cathode materials of waste lithium-ion batteries is the hydrometallurgical process of sulfuric acid leaching. However, the recovery effect of the sulfuric acid leaching method is poor. Since the sulfuric acid leaching method has no selectivity, lithium and metals such as aluminum, copper, iron, nickel, cobalt, and manganese in the cathode material are leached synchronously. After losing a part of lithium in the processes of separating and recovering metals such as nickel, cobalt, and manganese, lithium can be enriched and recovered, resulting in a low recovery rate of lithium. Further, since a small amount of lithium will enter the nickel, cobalt, and manganese salt products and the by-product sodium sulfate, the quality of other products except lithium will also be reduced.

[0040] In addition, the reduction roasting method can also be used to treat the positive and negative powder materials of waste lithium-ion batteries. After treatment, the powder materials are leached by an aqueous solution to obtain nickel-cobalt-manganese slag and a lithium-rich solution, realizing the separation of lithium from other metals. However, on the one hand, due to the need for high-temperature roasting operations in the reduction roasting method, it is necessary to increase the investment in roasting equipment and roasting costs. On the other hand, there is still the problem of low lithium leaching rate.

[0041] An embodiment of the present application provides a method for recovering lithium from a lithium battery. In an embodiment of the method for recovering lithium from a lithium battery in the present application, with reference to Figure 1 , the method for recovering lithium from a lithium battery includes:

[0042] Step S10, obtaining the positive and negative mixed powder of the lithium battery to be recycled;

[0043] In this embodiment, it should be noted that the lithium battery to be recycled refers to a discarded ternary lithium battery that can be recycled for resources.

[0044] Specifically, after collecting the lithium battery to be recycled, the lithium battery to be recycled can be subjected to treatments such as crushing, sorting, pyrolysis, screening, etc. to obtain the positive and negative mixed powder of the lithium battery to be recycled, and the positive and negative mixed powder is obtained for resource recovery.

[0045] Step S20, performing low-acid leaching on the positive and negative mixed powder to obtain a low-acid leaching solution and low-acid leaching residue;

[0046] In this embodiment, specifically, a low-concentration acid solution, such as low-concentration hydrochloric acid, low-concentration nitric acid, low-concentration sulfuric acid, etc., is added to the positive and negative mixed powder to extract lithium in the positive and negative mixed powder. At the same time of extracting lithium, metals such as aluminum, copper, iron, nickel, cobalt, and manganese in the positive and negative mixed powder will also be leached out at any time. Therefore, after lithium in the positive and negative mixed powder is fully leached, through solid-liquid separation, a low-acid leaching solution containing lithium and metals such as aluminum, copper, iron, nickel, cobalt, and manganese, and low-acid leaching residue can be obtained. Among them, the specific concentration of the low-concentration acid solution, the type of the acid solution, and the leaching time of the leaching can all be determined through experiments so that lithium in the positive and negative mixed powder can be fully leached into the low-concentration acid solution. Full leaching means that the leaching rate of lithium is higher than a preset leaching rate threshold, and the preset leaching rate threshold can be determined according to big data and actual situations. This embodiment does not limit this. Nickel, cobalt, manganese and other metals that are not fully leached remain in the low-acid leaching residue.

[0047] Optionally, the step of performing low-acid leaching on the positive and negative mixed powder to obtain a low-acid leaching solution and low-acid leaching residue includes:

[0048] Add a first sulfuric acid solution and a reducing agent to the positive and negative electrode mixed powder so that the positive and negative electrode mixed powder is leached for 3 - 10 hours under the condition of a pH value of 1.5 - 2.5 to obtain a low - acid leaching solution and a low - acid leaching residue.

[0049] In this embodiment, specifically, add a low - concentration first sulfuric acid solution and a reducing agent to the positive and negative electrode mixed powder to extract lithium in the positive and negative electrode mixed powder, so that the positive and negative electrode mixed powder is leached for 3 - 10 hours under the condition of a pH value of 1.5 - 2.5, such as 3 hours, 5 hours, 8 hours, 10 hours, etc., thereby enabling the lithium in the positive and negative electrode mixed powder to be fully leached into the first sulfuric acid solution, obtaining a low - acid leaching solution containing lithium and metals such as aluminum, copper, iron, nickel, cobalt, manganese, etc., and a low - acid leaching residue. Among them, the concentration of the first sulfuric acid solution should enable the positive and negative electrode mixed powder to be leached under the condition of a pH value of 1.5 - 2.5, which can be specifically determined according to actual needs and actual test results, etc. The reducing agent can be sulfur dioxide, hydrogen peroxide, and / or ascorbic acid, etc. The reducing agent is used to increase the leaching rate of cobalt and manganese in the positive and negative electrode mixed powder. The addition amount of the reducing agent can be determined according to the estimated total amount of the metals to be reduced in the positive and negative electrode mixed powder. The metals to be reduced refer to the metals in the positive and negative electrode mixed powder that are difficult to be fully leached by acid leaching, such as cobalt, manganese, etc. Therefore, the leaching rate of each metal to be reduced can be increased by adding a reducing agent. The estimated total amount of the metals to be reduced can be determined according to experience, big data, or actual test results, etc., and this embodiment does not limit this.

[0050] In an implementable manner, the addition amount of the first sulfuric acid solution can be 2 - 4 times the mass of the positive and negative electrode mixed powder, such as 2 times, 3 times, 4 times, etc.

[0051] Optionally, the reducing agent includes sulfur dioxide and / or hydrogen peroxide, and the addition amount of the reducing agent is 1.2 - 2.5 times the total molar amount of cobalt and manganese in the positive and negative electrode mixed powder.

[0052] In this embodiment, the reducing agent includes sulfur dioxide and / or hydrogen peroxide. The addition amount of the reducing agent is determined according to the total molar amount of cobalt and manganese in the positive and negative electrode mixed powder. The addition amount of the reducing agent is 1.2 - 2.5 times the total molar amount of cobalt and manganese in the positive and negative electrode mixed powder, such as 1.2 times, 1.5 times, 2 times, 2.5 times, etc.

[0053] Optionally, after the step of performing low - acid leaching on the positive and negative electrode mixed powder to obtain a low - acid leaching solution and a low - acid leaching residue, the following steps are further included:

[0054] Step A10: Add a second sulfuric acid solution with a concentration of 250 - 300 g / L to the low-acid leaching residue. After high-acid leaching for 3 - 5 hours, add a reducing agent and continue leaching for 1 - 3 hours to obtain graphite residue and a high-acid leaching solution.

[0055] Step A20: After adjusting the pH value of the high-acid leaching solution, return it to the low-acid leaching process for low-acid leaching of the positive and negative electrode mixed powder.

[0056] In this embodiment, specifically, low-acid leaching has a good extraction effect on lithium, but there may still be many valuable but difficult-to-extract metals remaining in the low-acid leaching residue, such as nickel, cobalt, manganese, etc. Therefore, the obtained low-acid leaching residue can be further extracted. Add a second sulfuric acid solution with a concentration of 250 - 300 g / L to the low-acid leaching residue. After high-acid leaching for 3 - 5 hours (such as 3 hours, 4 hours, 5 hours, etc.), add a reducing agent and continue leaching for 1 - 3 hours (such as 1 hour, 2 hours, 3 hours, etc.) to obtain graphite residue and a high-acid leaching solution. The high-acid leaching solution may contain valuable but difficult-to-extract metals such as nickel, cobalt, manganese, etc. Therefore, the high-acid leaching solution can be returned to the low-acid leaching process. Adjust the pH value of the high-acid leaching solution to the pH value range required for low-acid leaching. After mixing with the low-concentration acid solution used for leaching the positive and negative electrode mixed powder in the low-acid leaching process, they can be used together for low-acid leaching of the positive and negative electrode mixed powder.

[0057] Step S30: Add iron powder to the low-acid leaching solution to obtain a copper-removed solution and a copper metal product.

[0058] In this embodiment, specifically, add sufficient iron powder to the low-acid leaching solution to displace the copper ions in the low-acid leaching solution. The displaced copper ions precipitate in the form of sponge copper. After solid-liquid separation, the sponge copper can be post-treated to obtain a copper metal product. The liquid after solid-liquid separation is the copper-removed solution. Among them, the addition amount of the iron powder should be able to fully react with the copper ions for displacement. To ensure the full progress of the displacement reaction, an excessive amount of iron powder exceeding the theoretical value can be added. The excessive iron powder can be recycled later, and a relatively low recovery cost can still be ensured.

[0059] Step S40: Perform oxidation treatment on the copper-removed solution to obtain an oxidized solid product and a first filtrate.

[0060] In this embodiment, specifically, by means of introducing air, oxygen, or adding an oxidizing agent, etc., oxidize the divalent iron in the copper-removed solution to trivalent iron so that the trivalent iron can fully react and combine with the lithium ions and sulfate ions in the copper-removed solution to form an oxidized solid product. After solid-liquid separation, the oxidized solid product and the first filtrate can be obtained.

[0061] Optionally, the oxidized solid product includes jarosite. The step of oxidizing the solution after copper removal to obtain the oxidized solid product and the first filtrate includes:

[0062] Adjust the pH value of the solution after copper removal to 1.5 - 2.0, adjust the temperature to 80 - 95 °C, add hydrogen peroxide for oxidation treatment for 3 - 8 hours to obtain jarosite and the first filtrate.

[0063] In this embodiment, specifically, after adjusting the pH value of the solution after copper removal to 1.5 - 2.0, heat it to adjust the temperature of the solution after copper removal to 80 - 95 °C, add hydrogen peroxide to oxidize divalent iron in the solution after copper removal for 3 - 8 hours, such as 3 hours, 5 hours, 8 hours, etc. After the oxidation treatment, the divalent iron in the solution after copper removal is oxidized to trivalent iron, and the trivalent iron fully reacts and combines with lithium ions and sulfate ions in the solution after copper removal to form jarosite and precipitate. After solid - liquid separation, jarosite and the first filtrate can be obtained.

[0064] Optionally, after the step of oxidizing the solution after copper removal to obtain the oxidized solid product and the first filtrate, the following steps are further included:

[0065] Step B10: Adjust the pH value of the first filtrate to 3.5 - 4.5 to obtain the second filter residue and the second filtrate;

[0066] Step B20: Add the second filter residue to the low - acid leaching process and perform low - acid leaching together with the positive and negative electrode mixed powder.

[0067] In this embodiment, specifically, add neutralizing agents such as nickel carbonate and / or nickel hydroxide to the first filtrate to adjust the pH value of the first filtrate to 3.5 - 4.5, so that iron and aluminum precipitate from the first filtrate. After solid - liquid separation, the second filter residue and the second filtrate are obtained. The second filtrate mainly contains metals such as nickel, cobalt, and manganese, which can be further separated and recovered. The separation and recovery of nickel, cobalt, manganese, etc. are similar to the prior art and will not be elaborated here. The second filter residue mainly contains iron and aluminum, as well as a small amount of valuable metals such as residual nickel, cobalt, and manganese. Therefore, the second filter residue can be added to the low - acid leaching process and perform low - acid leaching together with the positive and negative electrode mixed powder, which can reduce resource loss during the process and improve the recovery rate of various resources.

[0068] Step S50: Pulverize and perform neutralization precipitation on the oxidized solid product to obtain iron - aluminum slag and the first lithium - containing solution;

[0069] In this embodiment, specifically, after the obtained oxidized solid product is slurried, by adjusting the pH value, iron and aluminum are precipitated from the solution. After sufficient reaction, solid-liquid separation, washing and other treatments are carried out to obtain iron-aluminum slag and a first lithium-containing solution.

[0070] Optionally, the steps of slurrying and neutralizing and precipitating the oxidized solid product to obtain iron-aluminum slag and a first lithium-containing solution include:

[0071] Step S51, slurry the oxidized solid product, adjust the pH value to 0.5 - 1.0, and adjust the temperature to 80 - 90 °C to obtain a high-iron hot solution;

[0072] Step S52, add the high-iron hot solution and a neutralizing agent to a precipitation tank for neutralizing precipitation. Control the reaction temperature of the neutralizing precipitation to be 75 - 85 °C, the reaction pH value to be 2.0 - 3.8, and control the concentration of ferric iron in the mixed solution in the precipitation tank to be less than or equal to 1 g / L to obtain iron-aluminum slag and a first lithium-containing solution.

[0073] In this embodiment, specifically, after the oxide solid product is slurried, a third sulfuric acid solution with a pH value of 0.5 - 1.0 is added for sufficient dissolution. After dissolution, it is heated to 80 - 90 °C to obtain a high-iron hot solution, where the high-iron hot solution refers to a hot solution containing ferric iron; then the high-iron hot solution and a neutralizing agent are added to a precipitation tank at a preset speed, control the reaction temperature to be 75 - 85 °C, the reaction pH value to be 2.0 - 3.8, and goethite continuously precipitates as the high-iron hot solution is added. After precipitation is completed, solid-liquid separation and washing are carried out. The filter residue is the iron-aluminum slag, and the filtrate is the first lithium-containing solution. Among them, the neutralizing agent includes sodium carbonate, nickel carbonate, nickel hydroxide, etc. The preset speed should make the concentration of ferric iron in the mixed solution in the precipitation tank less than or equal to 1 g / L to ensure the formation of stable goethite crystal nuclei, and it can be specifically determined according to actual test results, etc.

[0074] Optionally, the reaction temperature of the neutralizing precipitation is 85 - 85 °C, and the reaction pH value is 2.5 - 3.5.

[0075] Optionally, the neutralizing agent includes sodium carbonate and / or nickel carbonate.

[0076] In an implementable manner, after the steps of slurrying and neutralizing and precipitating the oxidized solid product to obtain iron-aluminum slag and a first lithium-containing solution, it further includes:

[0077] Recycling the iron-aluminum slag to the iron powder.

[0078] In this embodiment, specifically, the iron-aluminum slag is recycled into the iron powder. After being mixed with the iron powder, it is used to displace copper in the low-acid leaching solution, so as to realize the recycling of the iron powder and reduce the cost of recovering lithium from lithium batteries.

[0079] Step S60: Recover lithium carbonate products from the first lithium-containing solution.

[0080] In this embodiment, specifically, after performing post-treatments such as purification on the first lithium-containing solution, or without performing post-treatments, carbonates are added to generate lithium carbonate precipitate. After solid-liquid separation, washing the precipitate and other post-treatments, lithium carbonate products are obtained.

[0081] Optionally, the step of recovering lithium carbonate products from the first lithium-containing solution includes:

[0082] Step S61: Adjust the pH value of the first lithium-containing solution to 9.5 - 10.5 to obtain a first filter residue and a second lithium-containing solution;

[0083] Step S62: Add sodium carbonate solution to the second lithium-containing solution. After solid-liquid separation, lithium carbonate products are obtained.

[0084] In this embodiment, specifically, liquid alkali or other alkaline solutions are added to the first lithium-containing solution to adjust the pH value of the first lithium-containing solution to 9.5 - 10.5, so that impurity metal ions such as nickel, cobalt, manganese, iron, and aluminum precipitate. After solid-liquid separation, a second lithium-containing solution and a first filter residue are obtained. Sodium carbonate solution is added to the second lithium-containing solution to generate lithium carbonate precipitate. After solid-liquid separation, washing the precipitate and other post-treatments, lithium carbonate products are obtained.

[0085] In an implementable manner, the concentration of the sodium carbonate solution can be 250 - 350 g / L, such as 250 g / L, 300 g / L, 350 g / L, etc.

[0086] Optionally, after the step of adjusting the pH value of the first lithium-containing solution to 9.5 - 10.5 to obtain a first filter residue and a second lithium-containing solution, the following is further included:

[0087] Return the first filter residue to the low-acid leaching process and perform low-acid leaching together with the positive and negative electrode mixed powder.

[0088] In this embodiment, specifically, the first filter residue contains impurity metals such as nickel, cobalt, manganese, iron, and aluminum. Therefore, the first filter residue can be added to the low-acid leaching process and perform low-acid leaching together with the positive and negative electrode mixed powder, which can reduce resource losses during the process and improve the recovery rate of various resources.

[0089] In an implementable manner, refer to Figure 2, the method for recovering lithium from lithium batteries comprises the following steps:

[0090] Obtain the battery black powder of the lithium battery, that is, the mixed powder of the positive and negative electrodes of the lithium battery, and perform low-acid leaching on the battery black powder in the presence of a reducing agent. The filter residue after pressure filtration is further subjected to high-acid leaching, and after pressure filtration, primary washing, and secondary washing, graphite slag and high-acid leaching filtrate are obtained. The filtrate after pressure filtration is subjected to iron powder replacement to obtain copper powder and the solution after copper precipitation. The pH value of the solution after copper precipitation is adjusted once to enable iron and lithium to combine to form a precipitate, while metal impurities such as nickel, cobalt, and manganese remain dissolved in the solution, and the separation of the iron-lithium reactant and metal impurities can be achieved by pressure filtration. After pressure filtration, the solution containing metal impurities is adjusted twice to enable iron and aluminum to form a precipitate and precipitate out. The filter residue after filtration can be processed and returned to the low-acid leaching process to extract nickel, cobalt, and manganese again. A large amount of nickel, cobalt, and manganese are contained in the filtrate after filtration, and can be separated and recovered by means such as extraction. The iron-lithium reactant after pressure filtration is a solid. After pulping, it is dissolved with acid, and the iron and aluminum in the iron-lithium reactant are separated from lithium by adjusting the pH value and reducing ferric iron, and an iron-aluminum slag precipitate is formed. The iron-aluminum slag precipitate can be recycled after being mixed with iron powder, while lithium ions remain in the solution. At this time, there may still be a small amount of residual impurity metals in the lithium-containing solution, and the impurity metals can be removed by precipitation by adjusting the pH value to alkaline. The purity of lithium ions in the filtrate after impurity removal by precipitation is relatively high, and lithium carbonate products can be obtained by adding carbonate.

[0091] In this embodiment, by obtaining the mixed powder of the positive and negative electrodes of the lithium battery to be recycled, performing low-acid leaching on the mixed powder of the positive and negative electrodes to obtain a low-acid leaching solution and a low-acid leaching residue, the leaching of lithium and metals such as nickel, cobalt, and manganese is realized. Then, by adding iron powder to the low-acid leaching solution, a solution after copper removal and a copper metal product are obtained, realizing the replacement of iron and copper. Then, by performing oxidation treatment on the solution after copper removal, an oxidized solid product and a first filtrate are obtained, realizing the separation of lithium and metals such as nickel, cobalt, and manganese. Then, by performing pulping and neutralization precipitation on the oxidized solid product, an iron-aluminum slag and a first lithium-containing solution are obtained, realizing the separation of iron and lithium. Then, by recovering a lithium carbonate product from the first lithium-containing solution, the recovery of lithium in the lithium battery is realized. On the one hand, compared with the method of recovering lithium by sulfuric acid leaching, after lithium and metals such as aluminum, copper, iron, nickel, cobalt, and manganese are simultaneously leached in this application, by forming an oxidized solid product by the combination of lithium and iron and precipitating it from the solution, the separation of lithium and metals such as nickel, cobalt, and manganese is realized, effectively avoiding the loss of lithium in the separation and recovery process of metals such as nickel, cobalt, and manganese, improving the recovery rate of lithium recovered from the lithium battery, and overcoming the technical problem of the low recovery rate of lithium recovered from the lithium battery in the prior art. On the other hand, compared with the reduction roasting method, the method for recovering lithium in this application is simple and does not require high-temperature roasting operations, so the investment in roasting equipment and the roasting cost can be effectively reduced. That is, this application can realize the recovery of lithium from the lithium battery with low cost and high recovery rate.

[0092] The above are only the preferred embodiments of this application, and do not limit the patent scope of this application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be included in the patent scope of this application by the same token.

Claims

1. A method for recovering lithium from a lithium battery, characterized in that, The method for recovering lithium from lithium batteries comprises the following steps; Obtain the mixed powder of the positive and negative electrodes of the lithium battery to be recycled; Add a first sulfuric acid solution and a reducing agent to the mixed powder of the positive and negative electrodes, so that the mixed powder of the positive and negative electrodes is leached for 3-10 hours under the condition of a pH value of 1.5-2.5 to obtain a low-acid leaching solution and a low-acid leaching residue, wherein the reducing agent comprises sulfur dioxide and / or hydrogen peroxide, and the addition amount of the reducing agent is 1.2-2.5 times the total molar amount of cobalt and manganese in the mixed powder of the positive and negative electrodes; Add iron powder to the low-acid leaching solution to obtain a solution after copper removal and a copper metal product; Adjust the pH value of the solution after copper removal to 1.5-2.0, adjust the temperature to 80-95 °C, add hydrogen peroxide for oxidation treatment, and oxidize for 3-8 hours to obtain an oxidized solid product and a first filtrate, wherein the oxidized solid product comprises: jarosite; Pulpify the oxidized solid product and perform neutralization precipitation to obtain an iron-aluminum slag and a first lithium-containing solution; Recover lithium carbonate products from the first lithium-containing solution.

2. The method for recovering lithium from a lithium battery as claimed in claim 1, characterized in that, The step of pulpifying the oxidized solid product and performing neutralization precipitation to obtain an iron-aluminum slag and a first lithium-containing solution comprises: Pulpify the oxidized solid product, adjust the pH value to 0.5-1.0, and adjust the temperature to 80-90 °C to obtain a high-iron hot solution; Add the high-iron hot solution and a neutralizing agent to a precipitation tank for neutralization precipitation, control the reaction temperature of the neutralization precipitation to be 75-85 °C, the reaction pH value to be 2.0-3.8, and control the concentration of high-valent iron in the mixed solution in the precipitation tank to be less than or equal to 1 g / L to obtain an iron-aluminum slag and a first lithium-containing solution.

3. The method for recovering lithium from a lithium battery according to claim 2, wherein The reaction temperature of the neutralization precipitation is 85-85 °C, and the reaction pH value is 2.5-3.

5.

4. The method for recovering lithium from a lithium battery according to claim 2, characterized in that, The neutralizing agent comprises sodium carbonate and / or nickel carbonate.

5. The method for recovering lithium from a lithium battery as claimed in claim 1, wherein After the step of adding a first sulfuric acid solution and a reducing agent to the mixed powder of the positive and negative electrodes, so that the mixed powder of the positive and negative electrodes is leached for 3-10 hours under the condition of a pH value of 1.5-2.5 to obtain a low-acid leaching solution and a low-acid leaching residue, it further comprises: Add a second sulfuric acid solution with a concentration of 250-300 g / L to the low-acid leaching residue, perform high-acid leaching for 3-5 hours, add a reducing agent, and continue leaching for 1-3 hours to obtain a graphite slag and a high-acid leaching solution; After adjusting the pH value of the high-acid leaching solution, return it to the low-acid leaching process for low-acid leaching of the mixed powder of the positive and negative electrodes.

6. The method for recovering lithium from a lithium battery according to claim 1, wherein, The step of recovering lithium carbonate products from the first lithium-containing solution comprises: Adjust the pH value of the first lithium-containing solution to 9.5-10.5 to obtain a first filter residue and a second lithium-containing solution; Add a sodium carbonate solution to the second lithium-containing solution, and after solid-liquid separation, obtain lithium carbonate products.

7. The method for recovering lithium from a lithium battery as claimed in claim 6, wherein After the step of adjusting the pH value of the solution after copper removal to 1.5-2.0, adjusting the temperature to 80-95 °C, adding hydrogen peroxide for oxidation treatment, and oxidizing for 3-8 hours to obtain an oxidized solid product and a first filtrate, it further comprises: Adjust the pH value of the first filtrate to 3.5-4.5 to obtain a second filter residue and a second filtrate; Return the second filter residue to the low-acid leaching process and perform low-acid leaching together with the positive and negative electrode mixed powder; And / or, after the step of adjusting the pH value of the first lithium-containing solution to 9.5 - 10.5 to obtain a first filter residue and a second lithium-containing solution, the following steps are further included: Return the first filter residue to the low-acid leaching process and perform low-acid leaching together with the positive and negative electrode mixed powder.

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