Method and system for recycling lithium-ion battery electrode powders

Abstract

This invention discloses a method and system for recovering lithium-ion battery electrode powder. The method includes: acid leaching of the electrode powder; purification of the leachate to obtain purified leachate; neutralization and precipitation of the purified leachate using a calcium-based neutralizing agent followed by hydrocyclone separation; filtration of the discharged underflow to obtain gypsum product; and obtaining lithium-containing filtrate and nickel, cobalt, and manganese precipitates that can be sold as MHP (Metal-to-Potassium Hydrocarbons); purification of the lithium-containing filtrate to obtain a lithium-containing solution; and precipitation of lithium by introducing carbon dioxide into the lithium-containing solution to obtain a lithium-precipitated liquid and a lithium carbonate slurry. This method avoids the energy-intensive evaporation and crystallization process, simplifies the process, reduces energy consumption and costs, achieves a high recovery rate, and yields products with high purity.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode recycling technology, and in particular to a low-cost, short-process method and system for recycling lithium-ion battery electrode powder. Background Technology

[0002] With the rapid development of new energy vehicles, the demand for power batteries, the heart of these vehicles, has also surged. Along with the rapid development of lithium batteries, a massive wave of retired lithium-ion batteries is following. Constrained by multiple pressures related to resources, environmental protection, and safety, the comprehensive recycling of spent lithium-ion batteries has become a crucial issue that must be addressed. In recent years, research on lithium battery recycling processes has been booming, and some processes have been successfully applied to industrial production with good results. Although the recycling processes for spent lithium-ion batteries are numerous and complex, they can be broadly divided into three steps: battery dismantling and crushing, heat treatment and physical sorting, and electrode powder and comprehensive recycling. The nickel, cobalt, manganese, and lithium contained in the electrode powder have extremely high recycling value and are the most important element in the entire battery recycling process.

[0003] The most common processing techniques currently available are as follows:

[0004] ①Comprehensive method and ion exchange method. First, the separated positive electrode material is fully dissolved in dilute hydrochloric acid to remove impurities, centrifuged, and the pH of the supernatant is adjusted to alkaline and pure oxygen is introduced to oxidize cobalt and nickel into trivalent ions. Then, the solution is repeatedly passed through a weakly acidic cation exchange resin, and cobalt and nickel are separated by elution with ammonium sulfate solutions of different concentrations. Cobalt complexes are eluted with sulfuric acid, while the cation exchange resin is regenerated. Finally, cobalt and lithium are deposited with oxalate.

[0005] ② Precipitation method. The positive and negative electrode mixed active materials of the separated current collector are leached online using H2SO4 + H2O2. The impurities in the leaching filtrate are removed by iron removal using the sodium ferrous sulfate method, copper is separated by extraction, aluminum is removed by hydrolysis precipitation, and then appropriate amounts of nickel sulfate, manganese sulfate or cobalt sulfate are added. Finally, nickel cobalt manganese carbonate precursor is prepared by carbonate coprecipitation method.

[0006] ③ Co-precipitation. The separated cathode fragments were fully dissolved in sodium hydroxide solution, and after impurity removal with P2O4, a mixed solution of H2SO4 and H2O2 was added to reduce the solution containing nickel, cobalt, and manganese. The molar ratio of the solution was adjusted to 1:1:1 using nickel sulfate, manganese sulfate, or cobalt sulfate. A certain amount of NH3 was added to prepare a ternary precursor of nickel, cobalt, and manganese. Finally, lithium carbonate was added to the ternary precursor and sintered at high temperature to obtain the lithium nickel cobalt manganese oxide ternary cathode material.

[0007] Chinese patent application CN109593963A discloses a new method for selectively recovering valuable metals from spent lithium batteries. First, sulfuric acid is used to leach the positive and negative electrode powders from spent ternary lithium-ion batteries. Then, nickel sulfate and cobalt sulfate are extracted from the leachate by extraction, or sodium hydroxide is added to obtain nickel-cobalt hydroxide precipitates. Finally, sodium carbonate is added to the remaining solution to precipitate lithium carbonate.

[0008] Chinese patent application CN109666799A discloses a method for separating and recovering valuable metals from waste lithium battery materials and its application. First, the battery cathode material is leached using sulfuric acid and a reducing agent (one or more of glucose, sucrose, vitamin C, grape seed extract, sodium thiosulfate, and sodium sulfite). Then, additives are added to the leachate to adjust the pH to 10-12, causing nickel, cobalt, and manganese ions in the leachate to co-precipitate. The solution is filtered to obtain a nickel-cobalt-manganese precipitate and a lithium-ion solution. Finally, the lithium-ion solution is concentrated to 20-45 g / L, and excess anhydrous sodium carbonate is added to react and obtain the precipitate lithium carbonate.

[0009] Chinese patent application CN109721110A discloses a method for obtaining nickel-cobalt-manganese hydroxide from active materials recovered from waste lithium batteries. First, the nickel-cobalt-manganese leachate obtained from waste power lithium batteries is kept at -20℃ to 10℃ and stirred for 0.1 to 5 hours. The precipitated crystalline salts are then filtered out to obtain a nickel-cobalt-manganese sulfate solution. Next, the total concentration of nickel, cobalt, and manganese ions in the above nickel-cobalt-manganese sulfate solution is adjusted to 1 to 3 mol / L, and ammonia is added to bring the system pH to 8 to 10 to initiate a complexation reaction. Then, the pH of the reaction system is adjusted to 10 to 12, and the mixture is aged. The filtered cake is washed and dried to obtain a nickel-cobalt-manganese tri-element complex hydroxide.

[0010] Chinese patent application CN111261967A discloses a method for recycling waste lithium batteries and the battery-grade nickel-cobalt-manganese mixed crystals prepared from the recycled materials. The method first separates the positive electrode powder, prepares a slurry, and leaches it to remove impurities. Then, a precipitant (any one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, sodium hydroxide, and ammonia water) is added. After solid-liquid separation, nickel-cobalt-manganese slag and a lithium-containing solution are obtained.

[0011] The inventors of this application have discovered that in the prior art, including the aforementioned documents, when using neutralization precipitation for recycling, the neutralizing reagents are all one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia. These neutralizing reagents can be categorized as sodium-based or ammonium-based reagents. However, in the sulfuric acid leaching solution system of electrode powder, regardless of whether the aforementioned sodium-based or ammonium-based reagents are used for neutralization, the neutralization product will generate corresponding water-soluble sulfates. For example, using sodium hydroxide will produce sodium sulfate, and using ammonia will produce ammonium sulfate. However, these water-soluble sulfates must be removed from the system through evaporation and crystallization. Whether using multi-effect steam evaporation or MVR evaporation, the energy consumption is enormous; furthermore, these reagents are relatively expensive, resulting in high reagent costs in the production process. On the other hand, the inventors of this application also discovered that in the subsequent production of lithium carbonate, the traditional process uses sodium carbonate as a lithium precipitation agent to precipitate lithium carbonate, which inevitably produces sodium sulfate. This salt solution also needs to be removed from the system by evaporation and crystallization. Similarly, this process also has the disadvantage of high energy consumption. Summary of the Invention

[0012] One embodiment of the present invention aims to provide a method and system for recycling lithium-ion battery electrode powder. This objective can be achieved through the following technical solutions:

[0013] According to an embodiment of the present invention, a method for recycling lithium-ion battery electrode powder is provided, comprising: acid leaching the electrode powder, purifying the leaching solution to obtain purified leaching solution; neutralizing and precipitating the purified leaching solution with a calcium-based neutralizing agent, separating it with a hydrocyclone to obtain a lithium-containing filtrate, removing impurities from the lithium-containing filtrate to obtain a lithium-containing solution; and precipitating lithium in the lithium-containing solution with carbon dioxide to obtain a lithium-precipitated liquid and a lithium carbonate slurry.

[0014] Optionally, the calcium-based neutralizing agent includes one or more of calcium oxide, calcium hydroxide, and calcium carbonate, and the pH value of the purified leachate is adjusted to 9-10 using the calcium-based neutralizing agent.

[0015] Optionally, the step of precipitating lithium in the lithium-containing solution with carbon dioxide includes: mixing carbon dioxide and the lithium-containing solution in a venturi tube, precipitating lithium using a cyclone sedimentation method after mixing, and collecting carbon dioxide during the precipitation process and returning it to the venturi tube for recycling.

[0016] Optionally, it further includes: returning the lithium-precipitated liquid as a pH adjuster to the leachate for purification, and / or returning the lithium-precipitated liquid to acid leaching for reprocessing.

[0017] Optionally, it also includes: using a portion of the lithium carbonate slurry for leaching purification, using a portion of the lithium carbonate slurry for removing impurities from the lithium-containing filtrate, and filtering the remaining lithium carbonate slurry to obtain the lithium carbonate product.

[0018] Optionally, the step of purifying the leachate includes: adjusting the pH of the leachate to 2.5-4.5, filtering to obtain filter residue and purified leachate after removing iron and aluminum, washing the filter residue to obtain iron-aluminum slag for sale, and returning the washing liquid to acid leaching; wherein the content of iron and aluminum in the purified leachate is both <0.1g / L.

[0019] Optionally, the step of removing impurities from the lithium-containing filtrate to obtain a lithium-containing solution further includes: treating the filter residue to prepare calcium carbonate and / or magnesium carbonate for sale.

[0020] Optionally, after separation using a hydrocyclone, a bottom stream and nickel-cobalt-manganese precipitate for sale are also obtained. The bottom stream is then acid-washed and filtered to obtain gypsum for sale, and the filtrate is returned to acid leaching. During acid washing, the acid solution is a dilute acid solution with a pH value of 1.5 to 2.0.

[0021] Optionally, during acid leaching, a two-stage leaching process is adopted, with sulfuric acid as the leaching agent and hydrogen peroxide as the reducing agent; wherein, the first-stage leaching solution is purified to obtain purified leaching solution; the second-stage leaching solution is returned to the first-stage leaching process and the filter cake of the second stage is washed to obtain graphite residue for sale, and the washing solution is returned to the first-stage leaching process.

[0022] Optionally, the electrode powder is a mixture obtained during the dismantling and crushing process of lithium-ion batteries, including positive electrode powder, negative electrode powder, and other metals and their compounds, wherein the other metals include copper, iron, aluminum, calcium and magnesium.

[0023] According to an embodiment of the present invention, a lithium-ion battery electrode powder recovery system is provided, comprising a leaching unit, a purification unit, a neutralization and precipitation unit, an impurity removal device, and a carbon dioxide lithium precipitation device connected in sequence. The leaching unit is used to acid-leach the electrode powder to obtain a leachate; the purification unit is used to purify the leachate to obtain a purified leachate; the neutralization and precipitation unit includes a hydrocyclone and has a calcium-based neutralizing agent inlet for neutralizing and precipitating the purified leachate by adding a calcium-based neutralizing agent, and then separating it using the hydrocyclone to obtain a lithium-containing filtrate; the impurity removal device is used to remove impurities from the lithium-containing filtrate to obtain a lithium-containing solution; and the carbon dioxide lithium precipitation device is used to precipitate lithium from the lithium-containing solution using carbon dioxide to obtain a lithium-precipitated liquid and a lithium carbonate slurry.

[0024] Optionally, the carbon dioxide lithium precipitation device includes: a venturi tube, a main body, and a lithium precipitation post-precipitation liquid tank connected in sequence, wherein the venturi tube has a lithium precipitation pre-precipitation liquid inlet, a carbon dioxide inlet, and a carbon dioxide return port; the lithium precipitation pre-precipitation liquid inlet is used to add a lithium-containing solution; the main body has a first carbon dioxide outlet, which is connected to a gas-liquid separator; the lithium precipitation post-precipitation liquid tank has a second carbon dioxide outlet; the gas outlet and the second carbon dioxide outlet of the gas-liquid separator are both connected to the carbon dioxide return port of the venturi tube.

[0025] Optionally, the main body is formed by connecting an upper straight cylindrical section and a lower conical section; the straight cylindrical section is provided with a mixed slurry inlet and a lithium precipitation liquid outlet; the main body is connected to a venturi tube through the mixed slurry inlet and to a lithium precipitation liquid tank through the lithium precipitation liquid outlet; the first carbon dioxide outlet is located in the straight cylindrical section; the conical section is provided with a lithium carbonate slurry outlet.

[0026] Optionally, the lithium-precipitated liquid tank is also connected to a leaching unit and / or a purification unit.

[0027] Optionally, the lithium carbonate slurry outlet is connected to a leaching unit and / or a purification device.

[0028] Optionally, the lithium carbonate slurry outlet is also connected to a filter device for filtering the lithium carbonate slurry to obtain lithium carbonate product.

[0029] Optionally, the hydrocyclone has an underflow port and an overflow port; a filter device is provided at the overflow port for filtering the overflow to obtain lithium-containing filtrate and nickel-cobalt-manganese precipitate; the underflow port is connected to a gypsum product preparation device for washing the underflow with an acid solution to obtain gypsum product, and the filtrate outlet of the gypsum product preparation device is connected to the leaching unit.

[0030] Optionally, the impurity removal device has a filter residue discharge outlet for discharging calcium carbonate and / or magnesium carbonate.

[0031] Optionally, the leaching unit includes two leaching devices and two washing devices connected in sequence. The filtrate outlet of the second leaching device and the washing liquid outlet of the second washing device are both connected to the inlet of the first leaching device. The second washing device also has a graphite slag discharge outlet.

[0032] Optionally, the purification unit includes two washing devices, wherein the washing liquid outlet of the second washing device is connected to the inlet of the first leaching device, and the second washing device also has an iron and aluminum slag discharge outlet.

[0033] Beneficial effects: By adopting the above-described implementation method, the energy-intensive evaporation and crystallization process is avoided, simplifying the process, reducing energy consumption and costs, achieving a high recovery rate, and obtaining high purity products. Furthermore, in the preferred embodiment, the use of a specific carbon dioxide lithium precipitation device can improve carbon dioxide utilization, thereby increasing lithium precipitation efficiency. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of a lithium-ion battery electrode powder recycling method according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the carbon dioxide lithium precipitation device used in the lithium-ion battery electrode powder recovery system in one embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the connection structure of a lithium-ion battery electrode powder recycling system in one embodiment of the present invention.

[0037] Figure reference numerals: 1 Venturi tube, 2 straight section, 3 conical section, 4 lithium precipitation liquid outlet, 5 first carbon dioxide outlet, 6 gas-liquid separator, 7 lithium carbonate slurry outlet, 8 lithium precipitation liquid tank. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] As described in the background section of this application, the inventors discovered that the recycling of lithium-ion battery electrode powder requires a high-energy-consuming process of evaporation and crystallization. Based on this, the invention improves the lithium-ion battery electrode powder recycling method, avoiding this energy-intensive process and reducing recycling costs. This application innovates the neutralization and precipitation process by selecting an inexpensive neutralizing agent that avoids the production of soluble salts as a byproduct of the neutralization process, thereby avoiding the high-energy-consuming evaporation and crystallization process and reducing reagent costs in the production process. This application also innovates the lithium precipitation process by selecting an inexpensive lithium precipitation agent that avoids the production of soluble salts as a byproduct of the lithium precipitation process and improving the lithium precipitation device, thereby avoiding the high-energy-consuming evaporation and crystallization process and reducing reagent costs in the production process. Using the innovative neutralizing agent and lithium precipitation agent, the improved system achieves optimal recycling results for lithium-ion battery electrode powder.

[0040] Lithium-ion batteries are a novel type of battery that uses lithium-containing compounds as the positive electrode material and lithium-intercalated carbon as the negative electrode. The positive electrode materials for lithium-ion batteries involved in this application include: LixCoO2, LixNiO2, LixMnO4, and Li(NiO2). x Co y Mn 1-x-y O2 or Li(Ni) x Co y Al 1-x-y )O 2. Electrode powder refers to the mixture obtained during the dismantling and crushing process of lithium-ion batteries. It is a mixture of positive electrode powder, negative electrode powder, and small amounts of copper, iron, aluminum, etc.

[0041] Figure 3 The diagram illustrates the connection structure of a lithium-ion battery electrode powder recycling system in one embodiment of the present invention.

[0042] like Figure 3 As shown, the lithium-ion battery electrode powder recovery system in this embodiment includes: a leaching unit, a purification unit, a neutralization and precipitation unit, a purification device, and a carbon dioxide lithium precipitation device. Furthermore, the lithium precipitation tank 8 is connected to both the leaching unit and the purification unit, and the lithium carbonate slurry outlet 7 is connected to both the inlet / outlet unit and the purification device. Additionally, the lithium carbonate slurry outlet 7 is connected to a filtration device, through which commercially available lithium carbonate products are obtained.

[0043] The leaching unit may include two leaching devices and two washing devices connected in sequence. The graphite residue can be discharged after being washed by the two washing devices. The filtrate outlet of the two leaching devices and the washing liquid outlet of the two washing devices are both connected to the inlet of the first leaching device for reprocessing to improve processing efficiency.

[0044] The purification unit may include two washing devices. After washing by the two washing devices, the iron and aluminum slag that can be sold is discharged. The washing liquid outlets of the two washing devices are connected to the inlet of the first leaching device for further treatment to improve the processing efficiency.

[0045] The neutralization and precipitation unit includes a calcium-based neutralizing agent inlet for neutralization and precipitation. The unit also includes a hydrocyclone. A bottom outlet is located at the bottom of the hydrocyclone for discharging the underflow, which is then processed to obtain commercially available gypsum. An overflow outlet is located at the top of the hydrocyclone; the overflow undergoes solid-liquid separation to obtain a lithium-containing filtrate and commercially available nickel-cobalt-manganese precipitate.

[0046] The impurity removal device removes impurities from the lithium-containing filtrate obtained after filtration overflow to obtain a lithium-containing solution. This lithium-containing solution is then sent to the carbon dioxide lithium precipitation device as a pre-precipitation liquid for lithium precipitation, thereby improving the utilization rate of carbon dioxide while ensuring recovery efficiency.

[0047] Figure 2 The schematic diagram illustrates the structure of a carbon dioxide lithium precipitation device used in a lithium-ion battery electrode powder recovery system in one embodiment.

[0048] like Figure 2 As shown, the carbon dioxide lithium precipitation device includes a Venturi tube 1, a main body, and a lithium precipitation post-precipitation liquid tank 8 connected in sequence, and also includes a gas-liquid separator 6. The Venturi tube 1 has a pre-precipitation liquid inlet, a carbon dioxide inlet, a carbon dioxide return outlet, and a mixed slurry outlet. The Venturi tube 1 is horizontally arranged, allowing the mixed slurry to enter the straight cylindrical section 2 of the main body tangentially. The main body is formed by connecting the upper straight cylindrical section 2 and the lower inverted conical section 3. The straight cylindrical section 2 has a mixed slurry inlet connected to the mixed slurry outlet, and a first carbon dioxide outlet 5 and a lithium precipitation post-precipitation liquid outlet 4 at the top. The first carbon dioxide outlet 5 is connected to the carbon dioxide return outlet via the gas-liquid separator 6, and the lithium precipitation post-precipitation liquid outlet 4 is connected to the lithium precipitation post-precipitation liquid tank 8. The top of the lithium precipitation post-precipitation liquid tank 8 has a second carbon dioxide outlet, which is connected to the carbon dioxide return outlet. The bottom of the conical section 3 is a lithium carbonate slurry outlet 7, which is connected to a purification device and a purification unit, and also to a filter device to obtain lithium carbonate product. The bottom of the lithium-precipitated liquid tank 8 has a lithium-precipitated liquid outlet, which is connected to the purification unit and the leaching device.

[0049] This embodiment employs an improved carbon dioxide lithium precipitation device, enhancing carbon dioxide utilization and electrode powder recovery efficiency. By adding a Venturi tube 1 before the carbon dioxide lithium precipitation device, the carbon dioxide is thoroughly mixed with the pre-precipitation liquid before entering the device for lithium precipitation. Unreacted carbon dioxide in the device is partially discharged through the first carbon dioxide outlet 5, separated by a gas-liquid separator 6, and then re-enters the Venturi tube 1; the remaining portion, along with the post-precipitation liquid, enters the post-precipitation liquid tank 8, exits through the exhaust port (second carbon dioxide outlet) at the top of the tank, and returns to the Venturi tube 1, achieving efficient carbon dioxide utilization. Specifically, after the mixed slurry enters the carbon dioxide lithium precipitation device, it undergoes a downward spiral motion. Simultaneously, the pre-precipitation liquid and carbon dioxide fully contact and react, generating lithium carbonate precipitate. The lithium carbonate precipitate, under the influence of centrifugal force, is thrown against the cylinder wall and sinks to the bottom of the conical section 3 with the downward swirling flow, resulting in discharge. The clear liquid becomes an upward inner swirling flow and is discharged from the top of the straight section 2. During this process, the carbon dioxide released from the slurry forms a negative pressure column in the inner vortex center. Part of it is discharged with the clear liquid and enters the lithium precipitation tank 8, while the other part is discharged through the first carbon dioxide outlet 5. After being separated by the gas-liquid separator 6, it re-enters the venturi tube 1. The carbon dioxide entering the lithium precipitation tank 8 is discharged from the top of the tank and returns to the venturi tube 1, thereby improving the utilization rate of carbon dioxide.

[0050] Figure 1 The illustration schematically depicts the process flow of a lithium-ion battery electrode powder recovery method according to an embodiment of the present invention. The lithium-ion battery electrode powder recovery method provided in this application mainly includes three parts: leaching and purification, precipitation of nickel, cobalt, and manganese, and precipitation of lithium carbonate. The following is a detailed description... Figure 1 The lithium-ion battery electrode powder recycling method in this embodiment of the present invention will be further described, and may include the following steps:

[0051] Step S10: The electrode powder is acid-leached, the leachate is purified, and filtered to obtain a nickel-cobalt-manganese-lithium solution.

[0052] Sulfuric acid is used as the leaching agent and hydrogen peroxide as the reducing agent for a two-stage leaching process on ternary electrode powder. Specifically, in the leaching unit, sulfuric acid is used as the leaching agent while hydrogen peroxide is added as the reducing agent for the first stage leaching. The leachate obtained from the solid-liquid separation of the first stage leaching is sent to the purification process, and the leaching residue, i.e., the filter cake, is sent to the second stage leaching to continue leaching the remaining valuable metals. The second stage leaching also uses sulfuric acid as the leaching agent while hydrogen peroxide is added as the reducing agent. The filtrate obtained from the solid-liquid separation of the second stage leaching is returned to the first stage leaching. The leaching residue, i.e., the filter cake, is graphite residue. After two stages of washing with washing water, the graphite residue can be sold as a product, while the washing liquid is returned to the first stage leaching. By returning the filtrate and washing liquid for further processing, the recovery rate of each valuable metal can be further improved.

[0053] The first leaching stage yields a leachate, primarily composed of a mixed solution of nickel sulfate, cobalt sulfate, manganese sulfate, and lithium sulfate, along with trace amounts of iron and aluminum impurities. Before proceeding to the next nickel-cobalt-manganese precipitation step, it is crucial to remove these impurities as much as possible to maximize product purity. Specifically, in the purification unit, lithium precipitation solution and lithium carbonate slurry from subsequent processes are added to the leachate, adjusting the pH to 2.5–4.5. This causes the iron and aluminum impurities in the leachate to precipitate due to hydrolysis. Solid-liquid separation removes these precipitates from the solution, yielding a high-purity nickel-cobalt-manganese-lithium solution with iron and aluminum content both <0.1 g / L, achieving an iron and aluminum removal rate of approximately 99%. The resulting iron-aluminum slag undergoes a two-stage washing process. The slag can be sold as a product, while the washing liquid is returned to the first leaching stage to improve the recovery rate of valuable metals.

[0054] In addition, the first-stage leaching involves a reaction temperature of 70℃–80℃, a final pH value controlled at 1.5–3.0, and a reaction time of 1.5–2.5 hours. The second-stage leaching involves a liquid-to-solid ratio controlled at 5–7, a reaction temperature of 75℃–85℃, a final acidity controlled at 100 g / L–150 g / L, and a reaction time of 1.5–2.5 hours. By controlling these leaching parameters, the leaching efficiency is further improved, and the recovery rate of each product is higher.

[0055] Step S20: The nickel-cobalt-manganese-lithium solution is neutralized and precipitated using a calcium-based neutralizing agent, and then separated by cyclone separation. The underflow is discharged, and the overflow is filtered to obtain nickel-cobalt-manganese precipitate and lithium-containing filtrate.

[0056] A calcium-based neutralizing agent is added to the purified nickel-cobalt-manganese-lithium solution. The calcium-based neutralizing agent includes one or more of calcium oxide, calcium hydroxide, and calcium carbonate. In the neutralization and precipitation unit, the pH of the nickel-cobalt-manganese-lithium solution is adjusted to 9-10 by adding the calcium-based neutralizing agent to achieve neutralization and precipitation. At this time, nickel, cobalt, and manganese ions in the solution all precipitate, and the calcium in the neutralizing agent... 2+ Then react with SO4 in the solution 2- The reaction produces calcium sulfate precipitate.

[0057] However, the inventors of this application further discovered that calcium sulfate and the generated nickel-cobalt-manganese precipitate are both solids, and conventional solid-liquid separation methods cannot separate them. Based on this, this application utilizes the difference in sedimentation rates of calcium sulfate and nickel-cobalt-manganese precipitate in solution to efficiently separate them using a hydrocyclone, discharging the underflow and overflow. The underflow (gypsum slurry) can be discharged from the bottom of the hydrocyclone and can be filtered to prepare commercially available gypsum. The overflow is discharged from the top, and after filtration, the filter cake is nickel, cobalt, and manganese precipitate that can be sold as MHP. The filtrate is a lithium-containing filtrate (containing calcium and magnesium impurities) that enters the lithium precipitation process to recover the lithium.

[0058] In addition, the inventors of this application have also discovered that the gypsum products obtained by filtering the gypsum slurry as described above usually contain a small amount of nickel, cobalt, and manganese precipitates. In order to further improve the metal recovery rate, this application sends the underflow into the gypsum product preparation device and first washes the gypsum product with a dilute acid solution. The pH value of the dilute acid solution can be 1.5 to 2.0. Then, the gypsum product is filtered to obtain a relatively pure gypsum product. At this time, the purity of the gypsum product is ≥98%, and the washing liquid is returned to the leaching process, for example, it can be returned to the second stage leaching.

[0059] Step S30: Remove impurities from the lithium-containing filtrate (i.e., the filtrate after overflow filtration), filter to obtain a lithium-containing solution after impurity removal, introduce carbon dioxide into the lithium-containing solution to mix and precipitate lithium, and produce lithium carbonate slurry and lithium-precipitated liquid.

[0060] Impurity removal can be carried out in an impurity removal device. The main components of the lithium-containing filtrate are lithium hydroxide and small amounts of calcium and magnesium ions. In this application, impurities are removed before lithium precipitation, and the lithium carbonate slurry produced in subsequent processes is used to remove calcium and magnesium. The amount of lithium carbonate used is 1.1 to 1.3 times the theoretical total amount of calcium and magnesium. At this time, calcium and magnesium form insoluble carbonate precipitates and are removed from the system. Commercially available carbonates such as calcium carbonate can be prepared. The lithium-containing solution after impurity removal is used as the pre-precipitation liquid for lithium precipitation, which improves the lithium precipitation efficiency.

[0061] The lithium precipitation method of this application is to introduce carbon dioxide into the lithium-containing solution after calcium and magnesium removal, and to mix the carbon dioxide with the pre-precipitation liquid thoroughly for cyclone sedimentation to precipitate lithium. At this time, lithium hydroxide reacts with carbon dioxide to form lithium carbonate precipitate. The lithium carbonate slurry containing lithium carbonate precipitate is discharged from the bottom, and the post-precipitation liquid is collected in the post-precipitation liquid tank 8.

[0062] In addition, such as Figure 1 As shown, the lithium-precipitated liquid in the lithium-precipitated liquid tank 8 can be returned to the purification unit for iron and aluminum removal as a pH adjuster. The lithium-precipitated liquid in the lithium-precipitated liquid tank 8 can also be returned to the leaching unit for further processing. By returning the lithium-precipitated liquid to the iron and aluminum removal and first-stage leaching processes, it is recycled within the system, saving resources and simultaneously recovering unrecovered lithium from the lithium-precipitated liquid, thus improving the metal recovery rate.

[0063] In addition, such as Figure 1 As shown, the lithium carbonate slurry discharged from section 3 of the cone can be sent to a purification unit to remove iron and aluminum, or to a purification device to remove calcium and magnesium, or it can be directly filtered to obtain the product for sale (and the purity of the lithium carbonate product is ≥99.5%). By returning the lithium carbonate slurry to remove iron, aluminum, calcium, and magnesium, instead of conventional sodium carbonate, the introduction of sodium is avoided, and subsequent evaporation and crystallization operations are unnecessary, which greatly saves on one-time investment and production costs.

[0064] Furthermore, the lithium precipitation process is carried out in the aforementioned carbon dioxide lithium precipitation device. The pre-precipitation liquid and carbon dioxide are fully mixed in the venturi tube 1. The mixed slurry enters the straight section 2 and swirls to settle. The produced lithium carbonate settles to the bottom of the cone and is finally discharged from the lithium carbonate slurry outlet 7. The post-precipitation liquid rises slowly in the straight section 2 and continues to react with the unconsumed carbon dioxide. The produced lithium carbonate settles to the bottom of the cone section 3 and can be filtered and sold as a product with a purity of over 99.5%. The post-precipitation liquid flows out from the post-precipitation liquid outlet 4. The unreacted carbon dioxide is discharged from the first carbon dioxide exhaust port 5 above the straight section 2. After being separated by the gas-liquid separator 6, the gas returns to the venturi tube 1, and the liquid is discharged from the lower drain port. The post-precipitation liquid is discharged from the top post-precipitation liquid outlet 4 into the post-precipitation liquid tank 8. Some of the unreacted carbon dioxide in the post-precipitation liquid tank 8 can be discharged from the second carbon dioxide exhaust port above the post-precipitation liquid tank 8 and flow back to the venturi tube 1 for utilization. By using this carbon dioxide lithium precipitation device, the carbon dioxide utilization rate can reach over 90%. The lithium carbonate slurry can be filtered and sold as a product with a purity of over 99.5%. Lithium carbonate precipitation can be achieved by controlling the amount of carbon dioxide added. Specifically, the amount of carbon dioxide introduced should be 1.0 times the theoretical total amount of carbon dioxide reacting with lithium ions; it should not be excessive. This can be controlled through flow meter and valve interlocking.

[0065] The solution of this application will be further described below with reference to two specific embodiments:

[0066] Example 1

[0067] 1) The first-stage leaching reaction temperature is approximately 70℃, with the final pH value controlled at 2.0 and a reaction time of 2.0 hours. The second-stage leaching solution-to-solid ratio is controlled at approximately 6, the reaction temperature is 80℃, the final acidity is controlled at 100 g / L, and the reaction time is 2.0 hours. All of the second-stage leaching solution is returned to the first-stage leaching. The second-stage leaching residue is washed and sold as graphite product, while the wash water is returned to the second-stage leaching. Through two-stage leaching, the leaching rate of nickel, cobalt, manganese, and lithium can reach approximately 98.5%, and the purity of the graphite product can reach over 98%.

[0068] 2) The pH of the leaching solution is adjusted to approximately 3.5 by adding the lithium precipitation solution and lithium carbonate slurry from subsequent processes. This causes the iron and aluminum to hydrolyze and form precipitates, which are then removed by filtration. The resulting iron-aluminum slag is washed and sold or outsourced for further processing. The wash water is returned to the second-stage leaching. After purification, the iron and aluminum content in the solution is less than 0.1 g / L, achieving an iron and aluminum removal rate of approximately 99%.

[0069] 3) Add CaO to the purified leachate to control the final pH value to 9. At this point, nickel, cobalt, and manganese ions in the solution will all precipitate, and the CaO in the neutralizing agent will also precipitate. 2+ Then react with SO4 in the solution 2- The reaction produces calcium sulfate precipitate. The resulting slurry is passed into a hydrocyclone; the gypsum slurry is discharged from the bottom, while the overflow containing nickel-cobalt-manganese precipitate is discharged from the top. The overflow undergoes further solid-liquid separation to obtain a mixture of nickel-cobalt-manganese precipitate. The filtrate is sent to a purification unit as a pre-treatment for calcium and magnesium removal. In this embodiment, the gypsum and nickel-cobalt-manganese precipitate are separated using a hydrocyclone. The gypsum content entrained in the nickel-cobalt-manganese precipitate is less than 1%, and the nickel-cobalt-manganese precipitate content entrained in the gypsum is less than 2%, which can be recovered through acid washing.

[0070] 4) The underflow from the hydrocyclone is washed with a dilute acid solution (pH 2.0). After filtration, the washing liquid is returned to the leaching process, while the washing residue is sold as gypsum product with a purity of up to 99%.

[0071] 5) Add lithium carbonate slurry from the lithium carbonate precipitation process to the pre-calcium and magnesium removal solution. The amount added is 1.1 times the theoretical amount for reaction with calcium and magnesium. At this point, calcium and magnesium form insoluble carbonate precipitates, which are removed from the system by filtration. The filtrate is then sent to the lithium precipitation process as the pre-lithiation solution to recover the lithium. The removal rate of calcium and magnesium can reach about 99%.

[0072] 6) Carbon dioxide is introduced into the pre-precipitation liquid to ensure thorough mixing of the two in the Venturi tube 1. The mixed slurry then enters the straight section 2 and the conical section 3 for swirling sedimentation, and the produced lithium carbonate settles at the bottom of the cone and is discharged. The post-precipitation liquid rises slowly in the straight section 2 and continues to react with unconsumed carbon dioxide, while the produced lithium carbonate settles at the bottom of the cone. The post-precipitation liquid flows out from the post-precipitation liquid outlet 4 into the post-precipitation liquid tank 8. Unreacted carbon dioxide is discharged from the carbon dioxide outlet 5 of the straight section 2 and, along with the carbon dioxide discharged from the post-precipitation liquid tank 8, flows back into the Venturi tube 1 via the gas-liquid separator 6. By controlling the amount of carbon dioxide added to be 1.0 times the theoretical total reaction amount of lithium ions, lithium carbonate precipitation can be obtained. After filtration, it can be sold as a lithium carbonate product with a purity of over 99.5%. Using the device provided by this invention, the utilization rate of carbon dioxide in the lithium precipitation process can reach over 90%.

[0073] Example 2

[0074] 1) The first-stage leaching reaction temperature is approximately 80℃, with the final pH value controlled at 2.0 and a reaction time of 2.0 hours. The second-stage leaching solution solid ratio is controlled at approximately 6, the reaction temperature is 80℃, the final acidity is controlled at 150 g / L, and the reaction time is 2.0 hours. All of the second-stage leaching solution is returned to the first-stage leaching. The second-stage leaching residue is washed and sold as graphite product, while the wash water is returned to the second-stage leaching. Through two-stage leaching, the leaching rate of nickel, cobalt, manganese, and lithium can reach approximately 99%, and the purity of the graphite product can reach over 98.5%.

[0075] 2) The pH of the leaching solution is adjusted to approximately 3.5 by adding the lithium precipitation solution and lithium carbonate slurry from subsequent processes. Iron and aluminum precipitate due to hydrolysis, which is removed by filtration. The resulting iron-aluminum slag is washed and sold or outsourced for further processing; the wash water is returned to the second-stage leaching. The purified solution contains less than 0.1 g / L of iron and aluminum, achieving an iron and aluminum removal rate of approximately 99%.

[0076] 3) Add Ca(OH)2 to the purified leachate to control the final pH value to 10. At this point, nickel, cobalt, and manganese ions in the solution will all precipitate, and the Ca in the neutralizing agent will also precipitate. 2+ Then react with SO4 in the solution 2- The reaction produces calcium sulfate precipitate. The resulting slurry is passed into a hydrocyclone; the gypsum slurry is discharged from the bottom, while the nickel-cobalt-manganese precipitate is discharged from the top. The overflow undergoes further solid-liquid separation to obtain a mixture of nickel-cobalt-manganese precipitates. The filtrate is sent to the impurity removal process as a pre-liquid for calcium and magnesium removal. The hydrocyclone separates the gypsum and nickel-cobalt-manganese precipitates. The gypsum content entrained in the nickel-cobalt-manganese precipitate is less than 1%, and the nickel-cobalt-manganese precipitate content entrained in the gypsum is less than 1.5%, which can be recovered through acid washing.

[0077] 4) The underflow from the hydrocyclone is washed with a dilute acid solution (pH 2.0). After filtration, the washing liquid is returned to the leaching process, while the washing residue is sold as gypsum product with a purity of up to 99%.

[0078] 5) Add lithium carbonate produced in the lithium carbonate precipitation process to the pre-calcium and magnesium removal solution. The amount added is 1.1 times the theoretical amount for reaction with calcium and magnesium. At this point, calcium and magnesium form insoluble carbonate precipitates, which are removed from the system by filtration. The filtrate is sent to the lithium precipitation process as the pre-lithiation solution to recover the lithium. The removal rate of calcium and magnesium can reach approximately 99%.

[0079] 6) Carbon dioxide is introduced into the pre-precipitation liquid, and the two are thoroughly mixed in the Venturi tube 1. The mixed slurry enters the straight section 2 and the conical section 3 for swirling sedimentation, and the produced lithium carbonate settles to the bottom of the cone and is discharged. The post-precipitation liquid rises slowly in the straight section 2 and continues to react with the unconsumed carbon dioxide, and the produced lithium carbonate settles to the bottom of the cone. The post-precipitation liquid flows out from the post-precipitation liquid outlet 4 into the post-precipitation liquid tank 8. The unreacted carbon dioxide is discharged from the carbon dioxide outlet 5 of the straight section 2, and flows back into the Venturi tube 1 along with the carbon dioxide discharged from the post-precipitation liquid tank 8 through the gas-liquid separator 6. By controlling the amount of carbon dioxide added to be 1.0 times the theoretical total amount of lithium ion reaction, lithium carbonate precipitation can be obtained. After filtration, it can be sold as lithium carbonate product with a purity of over 99.5%. Using the device provided by this invention, the utilization rate of carbon dioxide in the lithium precipitation process can reach over 90%.

[0080] Some embodiments of this application also have the following beneficial effects:

[0081] 1) Calcium-based neutralizing agents, including but not limited to calcium oxide, calcium hydroxide, and calcium carbonate, are used to precipitate nickel and manganese in one or more mixed solutions of nickel sulfate, cobalt sulfate, and manganese sulfate. Simultaneously, a hydrocyclone is used to separate the gypsum produced. The reaction process does not produce soluble salts as byproducts, thus avoiding the energy-intensive evaporation and crystallization process. Furthermore, calcium-based reagents (CaO, Ca(OH)2) are generally cheaper than sodium-based (NaOH, Na2CO3) or amino-based (NH4OH, (NH4)2CO3) reagents, thus significantly reducing reagent costs in the production process.

[0082] 2) The improved carbon dioxide lithium precipitation device precipitates lithium hydroxide. Carbon dioxide precipitation does not produce soluble salts as a byproduct, thus avoiding the energy-intensive evaporation and crystallization process. Moreover, compared to sodium carbonate, carbon dioxide is cheaper, significantly reducing reagent costs in the lithium precipitation process. In addition, compared to the traditional straight-through reaction device, the improved carbon dioxide lithium precipitation device of this application adds a Venturi tube 1 and a carbon dioxide recovery pipeline, resulting in a higher carbon dioxide utilization rate of over 90%.

[0083] 3) This application employs leaching and purification, precipitation with a calcium-based neutralizing agent followed by cyclone separation, and lithium precipitation using an improved device after impurity removal. This avoids the energy-intensive evaporation and crystallization process, reducing costs. The resulting lithium-precipitated liquid can be returned to the purification and / or leaching steps for reuse or further processing. The obtained lithium carbonate can be filtered and sold as a product, or returned to the impurity removal and purification steps for full utilization. This not only solves the problems of complex and lengthy processes in existing electrode powder recovery processes, but also avoids the evaporation and crystallization process, reducing the energy consumption level of existing recovery processes. It also addresses the issue of high reagent costs in existing recovery processes, and yields products with high purity, achieving the goal of efficient recovery.

[0084] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for recycling lithium-ion battery electrode powder, characterized in that, include: The electrode powder was acid-leached, and the leachate was purified to obtain a purified leachate. The purified leachate was neutralized and precipitated using a calcium-based neutralizing agent, and then separated using a hydrocyclone to obtain a lithium-containing filtrate. The lithium-containing filtrate was then purified to obtain a lithium-containing solution. Lithium precipitation using a carbon dioxide precipitation device includes: mixing carbon dioxide with the lithium-containing solution in a venturi tube, and then precipitating lithium using a cyclone sedimentation method to obtain a lithium-precipitated liquid and a lithium carbonate slurry. During the lithium precipitation process, carbon dioxide is collected and returned to the venturi tube for recycling. The carbon dioxide lithium precipitation device includes a Venturi tube, a main body, and a lithium precipitation post-precipitation liquid tank connected in sequence. The Venturi tube has a lithium precipitation pre-precipitation liquid inlet for adding lithium-containing solution, a carbon dioxide inlet, a carbon dioxide return port, and a mixed slurry outlet. The main body is formed by connecting an upper straight cylindrical section and a lower conical section. The straight cylindrical section is provided with a mixed slurry inlet and a lithium precipitation post-precipitation liquid outlet. The main body is connected to the mixed slurry outlet of the Venturi tube through the mixed slurry inlet, and the main body is connected to the lithium precipitation post-precipitation liquid tank through the lithium precipitation post-precipitation liquid outlet. The conical section is provided with a lithium carbonate slurry outlet. The straight cylindrical section is provided with a first carbon dioxide outlet. The first carbon dioxide outlet is connected to a gas-liquid separator. The lithium precipitation post-precipitation liquid tank has a second carbon dioxide outlet. The gas outlet and the second carbon dioxide outlet of the gas-liquid separator are both connected to the carbon dioxide return port of the Venturi tube.

2. The lithium-ion battery electrode powder recycling method as described in claim 1, characterized in that, The calcium-based neutralizing agent includes one or more of calcium oxide, calcium hydroxide, and calcium carbonate, and the pH value of the purified leachate is adjusted to 9-10 using the calcium-based neutralizing agent.

3. The method for recycling lithium-ion battery electrode powder as described in claim 1 or 2, characterized in that, Also includes: The lithium-precipitated liquid is returned to the leachate for purification as a pH adjuster, and / or the lithium-precipitated liquid is returned to the acid leaching for further treatment.

4. The lithium-ion battery electrode powder recycling method as described in claim 3, characterized in that, Also includes: Part of the lithium carbonate slurry is used for leaching solution purification, part of the lithium carbonate slurry is used for removing impurities from lithium-containing filtrate, and the remaining lithium carbonate slurry is filtered to obtain lithium carbonate product.

5. The lithium-ion battery electrode powder recycling method as described in claim 4, characterized in that, The step of purifying the leachate includes: adjusting the pH of the leachate to 2.5-4.5, filtering to obtain filter residue and purified leachate after removing iron and aluminum, washing the filter residue to obtain iron-aluminum slag for sale, and returning the washing liquid to acid leaching; wherein the content of iron and aluminum in the purified leachate is both <0.1g / L. And / or, the step of removing impurities from the lithium-containing filtrate to obtain a lithium-containing solution further includes: treating the filter residue to prepare calcium carbonate and / or magnesium carbonate for sale.

6. The method for recycling lithium-ion battery electrode powder as described in claim 1, characterized in that, After separation using a hydrocyclone, a bottom stream and nickel-cobalt-manganese precipitate for sale are obtained. The bottom stream is then acid-washed and filtered to obtain gypsum for sale, and the filtrate is returned to acid leaching. During acid washing, the acid solution is a dilute acid solution with a pH value of 1.5 to 2.

0.

7. The method for recycling lithium-ion battery electrode powder as described in claim 1, characterized in that, During acid leaching, a two-stage leaching process is adopted, with sulfuric acid as the leaching agent and hydrogen peroxide as the reducing agent. The first-stage leaching solution is purified to obtain a purified leaching solution. The second-stage leaching solution is returned to the first-stage leaching process, and the filter cake from the second stage is washed to obtain graphite residue for sale. The washing solution is then returned to the first-stage leaching process. And / or, the electrode powder is a mixture obtained during the dismantling and crushing process of lithium-ion batteries, including positive electrode powder, negative electrode powder, and other metals and their compounds, wherein the other metals include copper, iron, aluminum, calcium and magnesium.

8. A lithium-ion battery electrode powder recovery system used in the lithium-ion battery electrode powder recovery method according to any one of claims 1-7, characterized in that, It includes a leaching unit, a purification unit, a neutralization and precipitation unit, an impurity removal device, and a carbon dioxide lithium precipitation device connected in sequence. The leaching unit is used to acid leach electrode powder to obtain leaching solution; The purification unit is used to purify the leachate to obtain a purified leachate. The neutralization and precipitation unit includes a hydrocyclone and has a calcium-based neutralizing agent inlet for neutralizing and precipitating the purified leachate by adding a calcium-based neutralizing agent, and then separating it using a hydrocyclone to obtain a lithium-containing filtrate. The impurity removal device is used to remove impurities from the lithium-containing filtrate to obtain a lithium-containing solution; The carbon dioxide lithium precipitation device is used to precipitate lithium in a lithium-containing solution using carbon dioxide to obtain a lithium-precipitated liquid and a lithium carbonate slurry.

9. The lithium-ion battery electrode powder recycling system according to claim 8, characterized in that, The lithium precipitation tank is also connected to the leaching unit and / or purification unit. The lithium carbonate slurry outlet is connected to the leaching unit and / or the impurity removal device; The lithium carbonate slurry outlet is also connected to a filter device for filtering the lithium carbonate slurry to obtain lithium carbonate product.

10. The lithium-ion battery electrode powder recycling system according to claim 8, characterized in that, The hydrocyclone has an underflow port and an overflow port; a filter device is provided at the overflow port to filter the overflow to obtain lithium-containing filtrate and nickel-cobalt-manganese precipitate; the underflow port is connected to a gypsum product preparation device to wash the underflow with an acid solution to obtain gypsum product, and the filtrate outlet of the gypsum product preparation device is connected to the leaching unit. And / or, the impurity removal device has a filter residue discharge outlet for discharging calcium carbonate and / or magnesium carbonate.

11. The lithium-ion battery electrode powder recycling system according to claim 8, characterized in that, The leaching unit includes two leaching devices and two washing devices connected in sequence. The filtrate outlet of the second leaching device and the washing liquid outlet of the second washing device are both connected to the inlet of the first leaching device. The second washing device also has a graphite slag discharge outlet. And / or, the purification unit includes two washing devices, wherein the washing liquid outlet of the second washing device is connected to the inlet of the first leaching device, and the second washing device also has an iron and aluminum slag discharge outlet.

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