A method for recovering lithium from retired lithium-ion batteries

Abstract

The present disclosure relates to a method for recovering lithium from retired lithium-ion batteries. The method includes the following steps: mixing a reducing agent into the powder of retired ternary lithium-ion batteries for reduction to obtain reduced battery powder; initial acid leaching: adding a part of the reduced battery powder into sulfuric acid, and filtering to obtain a first-stage leaching solution and a first-stage leaching residue; cyclic acid leaching: replacing the sulfuric acid used in the initial acid leaching with the second-stage leaching solution to leach new reduced battery powder, obtaining a lithium sulfate solution and a cyclic first-stage residue. Flowing the lithium sulfate solution into a calcium and magnesium removal resin, and then electrolyzing to obtain a lithium hydroxide solution; then passing through a nanofiltration membrane system for nanofiltration, and finally evaporating and crystallizing the nanofiltrate to obtain battery-grade lithium hydroxide.

Description

Technical Field

[0001] The present disclosure relates to a method for recovering lithium from retired lithium-ion batteries. Background Art

[0002] With the rapid development of new energy electric vehicles, the demand for lithium carbonate and lithium hydroxide, the raw materials of lithium batteries, is continuously expanding. Affected by the uneven distribution of global lithium resources and the limitation of exploitable reserves, lithium recovery has received extensive attention, especially the recovery of retired lithium-ion batteries, which has made the extraction and recovery of lithium resources from retired lithium-ion batteries enter the fast lane of development.

[0003] The recovery of retired lithium-ion batteries is mainly divided into two major methods: pyrometallurgy and hydrometallurgy. Pyrometallurgy directly uses high-temperature treatment methods to extract metals or metal oxides in the electrodes; hydrometallurgy is to first disassemble the battery shell, obtain electrode materials after crushing and screening, leach the positive electrode powder with acid, and the metals enter the leaching solution in the form of ions, and then valuable metals are separated one by one through methods such as precipitation separation, solvent extraction, electrodeposition, and ion exchange to obtain single-metal products or metal compounds.

[0004] And to make lithium-containing raw materials into lithium salt products, the main processes for large-scale industrial production of lithium hydroxide currently are: lithium sulfate causticization method and lithium carbonate causticization method. The lithium sulfate causticization method uses a freezing treatment method to separate mirabilite and lithium hydroxide. The process is short and the technology is mature, but there are problems of high energy consumption and product quality. Sodium sulfate will be entrained in the lithium hydroxide; the lithium carbonate causticization method has a mature process, a short production process, and low energy consumption, but higher-purity raw materials are required in production, the impurity removal process is complex, and the recovery rate is relatively low.

[0005] Patent CN111206154A separates nickel, cobalt, manganese, and lithium in the leaching solution through an extraction process. Using the leaching solution of waste ternary battery materials as the raw material, the leaching solution contains metal ions such as nickel, cobalt, manganese, and lithium. A new extraction system is used to selectively extract and separate valuable metals of nickel, cobalt, manganese, and lithium in sequence. Lithium is recovered in the final tail liquid. During the pretreatment process, with the removal of nickel, cobalt, and manganese, there will be a lot of lithium loss, which is not conducive to the realization of lithium resource utilization.

[0006] Patent CN110395748A adds alkali to the lithium extraction acid leaching solution of ore for causticization reaction to obtain a mixed solution of lithium hydroxide and sodium sulfate, and then separates sodium sulfate through a nanofiltration membrane. This process requires multi-stage nanofiltration treatment and is prone to lithium loss due to the limitation of the concentration multiple. Summary of the Invention

[0007] Based on this, the present disclosure aims to provide a method for recovering lithium from retired lithium-ion batteries. This method uses a combined pyrometallurgical and hydrometallurgical process to selectively recover lithium from retired lithium-ion batteries. This novel process produces battery-grade lithium hydroxide, providing a recycling process for lithium-ion battery cathode material.

[0008] The present disclosure discloses a method for recovering lithium from retired lithium-ion batteries, comprising the following steps:

[0009] Mixing a reducing agent into retired ternary lithium-ion battery powder for reduction to obtain reduced battery powder;

[0010] Initial acid leaching: adding a portion of the reduced battery powder into sulfuric acid, and filtering to obtain an initial leachate and an initial leach residue;

[0011] Circulating acid leaching:

[0012] Circular acid leaching stage 1: adding another portion of the reduced battery powder into the sulfate solution, filtering to obtain a lithium sulfate solution and a leaching residue from the circular stage 1;

[0013] Circulating acid leaching stage 2: adding the leaching residue from the circulating stage 1 into sulfuric acid and filtering to obtain the circulating stage 2 leaching solution and nickel-cobalt-manganese slag;

[0014] The sulfate solution is at least one of the initial leachate or the second-stage leaching solution of the circulation; the amount of sulfate in the first stage of the circulation acid leaching is added according to the molar ratio of sulfate to lithium ion of (1-1.5):2;

[0015] The lithium sulfate solution is flowed into a calcium and magnesium removal resin to obtain a purified lithium sulfate solution;

[0016] electrolyzing the purified lithium sulfate solution to obtain recovered sulfuric acid and lithium hydroxide solution;

[0017] Nanofiltration of the lithium hydroxide solution through a nanofiltration membrane system to obtain a purified lithium hydroxide solution;

[0018] The purified lithium hydroxide solution is evaporated and crystallized to obtain battery-grade lithium hydroxide and an evaporated mother liquor.

[0019] The present invention adopts a treatment process combining pyrometallurgy and hydrometallurgy to highly selectively recover lithium from retired lithium-ion batteries, and produces battery-grade lithium hydroxide through a treatment process of removing calcium and magnesium ions, electrolysis, nanofiltration, and crystallization, thereby avoiding the loss of a large amount of lithium resources.

[0020] During the reduction process of retired ternary lithium-ion battery powder, nickel, cobalt and manganese are precipitated as metal elements or oxides, and lithium is precipitated as lithium carbonate. That is, the main components of the reduced battery powder are nickel and cobalt elements, manganese oxide and lithium carbonate.

[0021] The main equations of the initial acid leaching process of the present disclosure are:

[0022] Ni / Co+H2SO4=Ni / CoSO4+H2↑;

[0023] MnO+H2SO4=MnSO4+H2O;

[0024] Li2CO3+H2SO4=Li2SO4+H2O+CO2↑.

[0025] Circulating acid leaching stage:

[0026] Ni / Co / MnSO4+Li2CO3=Ni / Co / MnCO3+Li2SO4;

[0027] Circulating acid leaching stage 2:

[0028] Ni / Co+H2SO4=Ni / CoSO4+H2↑;

[0029] MnO+H2SO4=MnSO4+H2O;

[0030] Li2CO3+H2SO4=Li2SO4+H2O+CO2↑.

[0031] In the initial acid leaching, the initial leaching solution contains nickel sulfate, cobalt sulfate, manganese sulfate and lithium sulfate, and the initial leaching residue is nickel-cobalt-manganese residue that is insoluble in sulfuric acid.

[0032] Since the initial leaching solution contains high contents of nickel sulfate, cobalt sulfate and manganese sulfate and cannot be directly used in subsequent processes, the present disclosure designs a cyclic acid leaching.

[0033] In the first stage of the circulating acid leaching process, the primary component of the leachate is lithium sulfate, while the primary components of the leach residue are unreacted nickel and cobalt, manganese oxide, and the reaction products of nickel carbonate, cobalt carbonate, and manganese carbonate. Because nickel sulfate, cobalt sulfate, and manganese sulfate react only with lithium carbonate in the reduced battery powder, the lithium sulfate content in the first stage leachate is relatively high.

[0034] In the second stage of circulating acid leaching, the leaching solution of the second stage of circulating acid leaching mainly contains nickel sulfate, cobalt sulfate and manganese sulfate, and the leaching residue of the second stage of circulating acid leaching mainly consists of nickel-cobalt-manganese slag insoluble in sulfuric acid, as well as lithium carbonate, nickel carbonate and cobalt carbonate.

[0035] The sulfate solution is at least one of the second-stage leaching solution or the circulating second-stage leaching solution, ensuring that the circulating acid leaching first stage and the circulating acid leaching second stage can be circulated.

[0036] The amount of sulfate in the first stage of the circulating acid leaching is added according to a molar ratio of sulfate to lithium ion of (1-1.5):2; that is, in the first stage of the circulating acid leaching, an appropriate amount or an excess of reduced battery powder is added to ensure that nickel sulfate, cobalt sulfate, and manganese sulfate in the second stage leachate or the circulating second stage leachate are completely reacted, ensuring that the lithium sulfate obtained by filtration has a high purity, thereby reducing the cost of subsequent processes.

[0037] The present invention discloses using calcium and magnesium removal resin to remove a small amount of calcium and magnesium ions in a lithium sulfate solution, thereby reducing the cost of a subsequent nanofiltration process.

[0038] The present invention uses electrolysis to treat lithium sulfate solution, converting the lithium sulfate solution into sulfuric acid and lithium hydroxide without introducing new components, thereby avoiding the generation of a large amount of waste residue that causes lithium loss and affects product purity.

[0039] The nanofiltration membrane used in the present disclosure is a charged membrane, which has selective permeability to ions and has a high retention rate for divalent and multivalent ions at a relatively low pressure, and can separate sulfate from lithium hydroxide solution.

[0040] The present disclosure adopts the coupled synergy of organic carbon reduction, sulfuric acid leaching and membrane separation to provide a new process for achieving the combination of highly selective lithium extraction and efficient impurity removal.

[0041] In one embodiment, the amount of sulfuric acid in the initial acid leaching of the present disclosure is added according to a molar ratio of sulfate to lithium ion of (1 to 1.5):1; the amount of sulfuric acid in the second stage of the cyclic acid leaching is added according to a molar ratio of sulfate to lithium ion of (1 to 1.5):2.

[0042] In the reduced battery powder, since the total molar amount of nickel, cobalt and manganese is close to the molar amount of lithium, in the initial acid leaching, an appropriate amount or excess of sulfuric acid is added based on the molar amount of lithium to fully leach the nickel, cobalt, manganese and lithium in the reduced battery powder; at the same time, since the reduced battery powder in the first stage of the cyclic acid leaching mainly reacts with lithium carbonate, and the reaction is complete, the main components of the leaching residue in the first stage of the cyclic acid leaching are nickel, cobalt and manganese oxide. Therefore, in the second stage of the cyclic acid leaching, an appropriate amount or excess of sulfuric acid is added based on the molar amount of lithium to fully leach the nickel, cobalt and manganese in the leaching residue in the first stage of the cyclic acid leaching;

[0043] In one embodiment, the cyclic acid leaching stage 1 and the cyclic acid leaching stage 2 described in the present disclosure are performed multiple times to reduce production costs.

[0044] In one embodiment, the reduction described in the present disclosure includes the following steps: Before reduction, an inert gas is introduced for 5 - 10 minutes in advance. Under the protection of the inert gas, the reducing agent can be converted into nanoscale amorphous carbon. If carried out under aerobic conditions, CO will be generated by the reducing agent. At this time, the generated CO still has a reduction effect, but it is not as good as the nanoscale amorphous carbon formed under anaerobic conditions in terms of sufficient contact with the raw material. Therefore, the reduction performance is second, which leads to insufficient leaching of lithium during the subsequent acid leaching process, resulting in lithium loss. The reduction is carried out in two stages of temperature: the first stage temperature is 200 - 500 °C, and the duration is 1 - 3 h. At this temperature and time, the reducing agent is converted into nanoscale amorphous carbon, which can contact the raw material sufficiently, making the reduction effect better; the second stage temperature is 500 - 650 °C, and the duration is 2 - 4 h. At this temperature and time, the nanoscale amorphous carbon is evenly distributed, making the ternary lithium-ion battery powder be fully reduced.

[0045] In one embodiment, the reducing agent described in the present disclosure is at least one of wood chips, straw, sucrose, fructose, maltose, lactose, starch, and glucose. The reducing agent has a low price and is easy to obtain.

[0046] The reaction process equation of the reducing agent is as follows (taking glucose as an example):

[0047] (1): C6H 12 O6 = 6H2O + 6C (nanoscale amorphous carbon);

[0048] (2): Li(Ni x Co y Mn 1-x-y )O2 + (1 + 2x + 2y) / 4C = 1 / 2Li2O + xNi + yCo + (1 - x - y)MnO + (1 + 2x + 2y) / 4CO2;

[0049] (3): Li2O + CO2 = Li2CO3.

[0050] In one embodiment, the dosage of the reducing agent described in the present disclosure is 5 - 30 wt% of the retired ternary lithium-ion battery powder. If the dosage of the reducing agent is too small, the ternary lithium-ion battery powder cannot be fully reduced, which will lead to insufficient leaching of lithium during the subsequent acid leaching process, resulting in lithium loss; if the dosage of the reducing agent is too large, the cost will increase.

[0051] In one embodiment, when the present disclosure reduces the battery powder during initial acid leaching and cyclic acid leaching, the sulfuric acid is concentrated sulfuric acid, and pure water needs to be added before adding the concentrated sulfuric acid. The mass ratio of the pure water to the reduced battery powder, that is, the liquid-solid ratio, is 3:1 - 10:1. If the liquid-solid ratio is too low, during subsequent operations, the acidity of the solution is too high, which requires high equipment requirements; if the liquid-solid ratio is too high, during subsequent operations, the acidity of the solution is too low, and the lithium in the reduced battery powder cannot be fully leached, resulting in lithium loss.

[0052] In one embodiment, the nanofiltration membrane system of the present disclosure has at least two stages. The multi-stage nanofiltration membrane system can efficiently separate sulfate radicals in the lithium hydroxide solution, effectively retain 98% of the sulfate radicals, thereby avoiding co-saturation during the evaporation and crystallization process, achieving one-step evaporation and crystallization to obtain battery-grade lithium hydroxide, reducing the investment in the MVR system (wastewater treatment system), and reducing costs.

[0053] In one embodiment, during the second-stage cyclic acid leaching of the present disclosure, the evaporation mother liquor is also added to reduce lithium loss during the recovery process.

[0054] In one embodiment, the leaching time for the initial acid leaching, the first stage of cyclic acid leaching, and the second stage of cyclic acid leaching of the present disclosure is 1 - 2 h, which can enable lithium to be fully leached.

[0055] The present disclosure combines organic carbon reduction, sulfuric acid leaching, and membrane separation synergistically, providing a new process for realizing the combination of high-selectivity lithium extraction and efficient impurity removal.

[0056] For better understanding and implementation, the present disclosure will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0057] Figure 1 It is a process flow chart for treating waste lithium-ion batteries. Detailed Embodiments

[0058] As Figure 1 shown, a method for recovering lithium from waste lithium-ion batteries of the present disclosure includes the following steps:

[0059] Mix a reducing agent into the waste ternary lithium-ion battery powder to obtain reduced battery powder;

[0060] Under a fixed liquid-solid ratio, add the reduced battery powder into pure water; add sulfuric acid according to the molar ratio of sulfate radicals to lithium ions for initial acid leaching, and filter to obtain an initial leachate and an initial leach residue.

[0061] Add the reduced battery powder into pure water; add a sulfate solution according to the molar ratio of sulfate radicals to lithium ions for the first stage of cyclic acid leaching, and filter to obtain a lithium sulfate solution and a first-stage cyclic leach residue; under a fixed liquid-solid ratio, add the first-stage cyclic leach residue into sulfuric acid for the second stage of cyclic acid leaching, and filter to obtain a second-stage cyclic leachate and a nickel-cobalt-manganese residue; the first stage of cyclic acid leaching and the second stage of cyclic acid leaching together constitute cyclic acid leaching;

[0062] The sulfate solution is at least one of the second-stage leachate or the second-stage cyclic leachate;

[0063] Flow the lithium sulfate solution through a calcium and magnesium removal resin to obtain a purified lithium sulfate solution;

[0064] Flow the purified lithium sulfate solution into a bipolar membrane electrodialysis system. After electrolysis, recycled sulfuric acid and lithium hydroxide solution are obtained.

[0065] Subject the lithium hydroxide solution to nanofiltration through a nanofiltration membrane to obtain a purified lithium hydroxide solution.

[0066] Evaporate and crystallize the purified lithium hydroxide solution to obtain battery-grade lithium hydroxide and evaporation mother liquor.

[0067] Through a treatment process combining pyrometallurgy and hydrometallurgy, the present disclosure highly selectively recovers lithium from retired lithium-ion batteries. Through a treatment process of removing calcium and magnesium ions, electrolysis, nanofiltration, and crystallization, battery-grade lithium hydroxide is produced, avoiding a large loss of lithium resources.

[0068] The main equations in the acid leaching process of the present disclosure are as follows:

[0069] Initial acid leaching and cyclic acid leaching, second stage:

[0070] Ni / Co + H2SO4 = Ni / CoSO4 + H2↑;

[0071] MnO + H2SO4 = MnSO4 + H2O;

[0072] Li2CO3 + H2SO4 = Li2SO4 + H2O + CO2↑;

[0073] Cyclic acid leaching, first stage:

[0074] Ni / Co / MnSO4 + Li2CO3 = Ni / Co / MnCO3 + Li2SO4.

[0075] The present disclosure uses a bipolar membrane electrodialysis system to treat the lithium sulfate solution, converting the lithium sulfate solution into sulfuric acid and lithium hydroxide without introducing new components, avoiding the generation of a large amount of waste residue that causes lithium loss and affects product purity.

[0076] The nanofiltration membrane adopted in the present disclosure is a charged membrane, which has selective permeability to ions. At a relatively low pressure, it has a high rejection rate for divalent and multivalent ions and can separate sulfate radicals in the lithium hydroxide solution.

[0077] The leaching time for the initial acid leaching, cyclic first-stage acid leaching, and cyclic second-stage acid leaching in the present disclosure is 1 - 2 h, which can fully leach lithium.

[0078] The present disclosure adopts the coupling and synergy of organic carbon reduction, sulfuric acid leaching, and membrane separation, providing a new process for realizing the combination of highly selective lithium extraction and efficient impurity removal.

[0079] Example 1

[0080] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0081] 1200g of retired ternary lithium-ion battery powder was mixed with 120g of glucose and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 350°C for 2h, and the second stage was at 650°C for 3h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0082] 500 g of reduced battery powder, in which the mass fraction of Li is 4.4 wt %, is added with 1500 g of pure water at a liquid-to-solid ratio of 3 / 1; 348 g of 98% concentrated sulfuric acid is added at a molar ratio of sulfate to lithium ion of 1.1:1 for initial acid leaching, and the initial leachate and initial leaching residue are obtained by filtration.

[0083] 500 g of reduced battery powder, wherein the mass fraction of Li is 4.4 wt %, pure water is added, and the initial leachate is added according to a molar ratio of sulfate to lithium ion of 1.1:2 for circulating acid leaching for one stage, and filtered to obtain a lithium sulfate solution and a first stage leaching residue, wherein the total mass of the pure water and the initial leachate is 1500 g; 1500 g of pure water is added to the first stage leaching residue of the circulation; 174 g of 98% concentrated sulfuric acid is added to carry out a second stage of circulating acid leaching, and after filtering, a second stage leaching solution and a nickel-cobalt-manganese slag are obtained; the first stage leaching and the second stage leaching together constitute a circulating acid leaching. In a process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed once;

[0084] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0085] Example 2

[0086] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0087] 1200g of retired ternary lithium-ion battery powder was mixed with 120g of glucose and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 350°C for 2h, and the second stage was at 650°C for 3h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0088] 500 g of reduced battery powder, in which the mass fraction of Li is 4.4 wt %, is added with 1500 g of pure water at a liquid-to-solid ratio of 3 / 1; 348 g of 98% concentrated sulfuric acid is added at a molar ratio of sulfate to lithium ion of 1.1:1 for initial acid leaching, and the initial leachate and initial leaching residue are obtained by filtration.

[0089] Take 500 g of reduced battery powder with the mass fraction of Li being 4.4 wt%, add pure water, and add the initial leaching solution according to the molar ratio of sulfate radical to lithium ion of 1.1:2 to carry out the first-stage cyclic acid leaching, and filter to obtain lithium sulfate solution and the first-stage leaching residue. Among them, the total mass of the pure water and the initial leaching solution is 1500 g; add 1500 g of pure water to the first-stage cyclic leaching residue; then add 174 g of 98% concentrated sulfuric acid to carry out the second-stage cyclic acid leaching, and after filtration, obtain the second-stage cyclic leaching solution and nickel-cobalt-manganese residue; the first-stage cyclic acid leaching and the second-stage cyclic acid leaching together constitute the cyclic acid leaching. In one technological process, the cyclic acid leaching is carried out multiple times and is carried out once in this embodiment;

[0090] Let the lithium sulfate solution flow into the calcium and magnesium removal resin and then transfer it to the bipolar membrane electrodialysis system, and concentrate the lithium hydroxide solution in the electrolytic alkali chamber. Remove the sulfate radical from the lithium hydroxide solution concentrated in the alkali chamber through three-stage nanofiltration, and carry out one-step evaporation crystallization on the clear liquid to obtain battery-grade lithium hydroxide.

[0091] Example 3

[0092] A method for recycling lithium from retired lithium-ion batteries, comprising the following specific steps: [[ID=IS]]

[0093] Take 1200 g of retired ternary lithium-ion battery powder, mix it with 120 g of glucose, and carry out two-stage high-temperature reduction in an atmosphere without nitrogen. The temperature of the first-stage reduction is 350 °C and the duration is 2 h. The temperature of the second-stage reduction is 650 °C and the duration is 3 h to obtain reduced battery powder, in which nickel, cobalt, and manganese are precipitated as metal elements or oxides, and lithium is precipitated as lithium carbonate.

[0094] Take 500 g of reduced battery powder with the mass fraction of Li being 4.2 wt%, add 1500 g of pure water at a liquid-solid ratio of 3 / 1; add 322 g of 98% concentrated sulfuric acid according to the molar ratio of sulfate radical to lithium ion of 1.1:1 to carry out the initial acid leaching, and filter to obtain the initial leaching solution and the initial leaching residue.

[0095] Take 500 g of reduced battery powder with the mass fraction of Li being 4.2 wt%, add pure water, and add the initial leaching solution according to the molar ratio of sulfate radical to lithium ion of 1.1:2 to carry out the first-stage cyclic acid leaching, and filter to obtain lithium sulfate solution and the first-stage leaching residue. Among them, the total mass of the pure water and the initial leaching solution is 1500 g; add 1500 g of pure water to the first-stage cyclic leaching residue; then add 166 g of 98% concentrated sulfuric acid to carry out the second-stage cyclic acid leaching, and after filtration, obtain the second-stage cyclic leaching solution and nickel-cobalt-manganese residue; the first-stage cyclic acid leaching and the second-stage cyclic acid leaching together constitute the cyclic acid leaching. In one technological process, the cyclic acid leaching is carried out multiple times and is carried out once in this embodiment;

[0096] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes three-stage nanofiltration to remove sulfate ions. The clear solution undergoes one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0097] Example 4

[0098] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0099] 1200g of retired ternary lithium-ion battery powder was mixed with 240g of fructose and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first reduction temperature was 200℃ and the duration was 3h, and the second reduction temperature was 600℃ and the duration was 2h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0100] Take 500g of reduced battery powder, in which the mass fraction of Li is 4.6wt%, add 2500g of pure water at a liquid-solid ratio of 5 / 1; add 430g of 98% concentrated sulfuric acid at a molar ratio of sulfate to lithium ion of 1.3:1 for initial acid leaching, and filter to obtain initial leachate and initial leaching residue.

[0101] 500 g of reduced battery powder, wherein the mass fraction of Li is 4.6 wt %, pure water is added, and the initial leachate is added according to a molar ratio of sulfate to lithium ion of 1.3:2 for circulating acid leaching for one stage, and filtered to obtain a lithium sulfate solution and a first stage leaching residue, wherein the total mass of the pure water and the initial leachate is 2500 g; 2500 g of pure water is added to the first stage leaching residue of the circulation; 215 g of 98% concentrated sulfuric acid is added for circulating acid leaching for the second stage, and after filtering, a circulating second stage leachate and nickel-cobalt-manganese slag are obtained; the first stage leaching and the second stage leaching together constitute a circulating acid leaching. In a process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed once;

[0102] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0103] Example 5

[0104] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0105] 1200g of retired ternary lithium-ion battery powder was mixed with 60g of sucrose and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at a temperature of 500°C for 1h, and the second stage was at a temperature of 550°C for 4h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0106] Take 500g of reduced battery powder, in which the mass fraction of Li is 4.2wt%, add 3500g of pure water at a liquid-solid ratio of 7 / 1; add 454g of 98% concentrated sulfuric acid at a molar ratio of sulfate to lithium ion of 1.5:1 for initial acid leaching, and filter to obtain initial leachate and initial leaching residue.

[0107] 500 g of reduced battery powder, wherein the mass fraction of Li is 4.2 wt %, pure water is added, and the initial leachate is added according to a molar ratio of sulfate to lithium ion of 1.5:2 for circulating acid leaching for one stage, and filtered to obtain a lithium sulfate solution and a first stage leaching residue, wherein the total mass of the pure water and the initial leachate is 3500 g; 3500 g of pure water is added to the first stage leaching residue of the circulation; 227 g of 98% concentrated sulfuric acid is added for circulating acid leaching for the second stage, and after filtering, a circulating second stage leachate and nickel-cobalt-manganese slag are obtained; the first stage leaching and the second stage leaching together constitute a circulating acid leaching. In a process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed once;

[0108] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0109] Example 6

[0110] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0111] 1200g of retired ternary lithium-ion battery powder was mixed with 360g of straw and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 400°C and lasted for 1h, and the second stage was at 500°C and lasted for 4h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0112] Take 500g of reduced battery powder, in which the mass fraction of Li is 4.2wt%, add 5000g of pure water at a liquid-solid ratio of 10 / 1; add 302g of 98% concentrated sulfuric acid at a molar ratio of sulfate to lithium ion of 1.2:1 for initial acid leaching, and filter to obtain initial leachate and initial leaching residue.

[0113] 500 g of reduced battery powder, wherein the mass fraction of Li is 4.4 wt %, pure water is added, and the initial leachate is added according to a molar ratio of sulfate to lithium ion of 1.2:2 for circulating acid leaching for one stage, and filtered to obtain a lithium sulfate solution and a first stage leaching residue, wherein the total mass of the pure water and the initial leachate is 5000 g; 5000 g of pure water is added to the first stage leaching residue of the circulation; 151 g of 98% concentrated sulfuric acid is added to carry out a second stage of circulating acid leaching, and after filtering, a second stage leaching solution and a nickel-cobalt-manganese slag are obtained; the first stage leaching and the second stage leaching together constitute a circulating acid leaching. In a process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed once;

[0114] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0115] Example 7

[0116] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0117] 1200g of retired ternary lithium-ion battery powder was mixed with 100g of sawdust and 100g of starch and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 400°C for 1h, and the second stage was at 650°C for 2h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0118] Take 500g of reduced battery powder, in which the mass fraction of Li is 4.5wt%, add 3000g of pure water at a liquid-solid ratio of 6 / 1; add 324g of 98% concentrated sulfuric acid at a molar ratio of sulfate to lithium ion of 1.2:1 for initial acid leaching, and filter to obtain initial leachate and initial leaching residue.

[0119] 500 g of reduced battery powder, wherein the mass fraction of Li is 4.5 wt %, pure water is added, and the initial leachate is added according to a molar ratio of sulfate to lithium ion of 1.2:2 for circulating acid leaching for one stage, and filtered to obtain a lithium sulfate solution and a first stage leaching residue, wherein the total mass of the pure water and the initial leachate is 3000 g; 3000 g of pure water is added to the first stage leaching residue of the circulation; 162 g of 98% concentrated sulfuric acid is added to carry out a second stage of circulating acid leaching, and after filtering, a second stage leaching solution and a nickel-cobalt-manganese slag are obtained; the first stage leaching and the second stage leaching together constitute a circulating acid leaching. In a process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed once;

[0120] The lithium sulfate solution flows into a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The solution is then enriched in an electrolytic alkaline chamber to produce a lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a one-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0121] Example 8

[0122] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0123] 6000g of retired ternary lithium-ion battery powder was mixed with 500g of maltose and 500g of lactose and subjected to two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 400°C for 1h, and the second stage was at 650°C for 2h to obtain reduced battery powder, in which nickel, cobalt and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate.

[0124] Take 500g of reduced battery powder, where the mass fraction of lithium is 5.0wt%, and add 4000g of pure water at a liquid-to-solid ratio of 8 / 1. Then add 360g of 98% concentrated sulfuric acid at a molar ratio of sulfate to lithium ion of 1.2:1 for initial acid leaching. Filter to obtain the initial leachate and initial leach residue. In a single process flow, the initial acid leaching is performed only once.

[0125] Take 500g of reduced battery powder, wherein the mass fraction of Li is 5.0wt%, add pure water, and add the initial leachate according to the molar ratio of sulfate to lithium ion of 1.2:2 for circulating acid leaching for one stage, filter to obtain lithium sulfate solution and one stage leaching residue, wherein the total mass of the pure water and the initial leachate is 4000g; add 4000g of pure water to the circulating first stage leaching residue; then add 180g of 98% concentrated sulfuric acid for circulating acid leaching for the second stage, filter to obtain the circulating second stage leachate and nickel-cobalt-manganese slag, and use the circulating second stage leachate for circulating leaching; the circulating first stage acid leaching and the circulating second stage acid leaching together constitute a circulating acid leaching, and in one process flow, the circulating acid leaching is performed multiple times, and in this embodiment, it is performed eight times;

[0126] The sulfate solution is the second-stage leaching solution or the circulating second-stage leaching solution.

[0127] The lithium sulfate solution flows into a calcium-magnesium removal resin and then into a bipolar membrane electrodialysis system. The lithium hydroxide solution is enriched in the electrolytic alkaline chamber. The sulfuric acid solution is then enriched and recovered in the acid chamber. The lithium hydroxide solution enriched in the alkaline chamber undergoes two-stage nanofiltration to remove sulfate ions. The clear solution undergoes a single-step evaporation and crystallization to produce battery-grade lithium hydroxide.

[0128] The process data for recovering lithium from retired lithium-ion batteries in Examples 1 to 8 were calculated and listed in Table 1.

[0129] Table 1 Process data of lithium recovery from retired lithium-ion batteries

[0130]

[0131]

[0132] The Li content (wt%) of the reduced battery powder is the mass fraction of lithium ions in the reduced battery powder;

[0133] The Li content (g / L) of lithium sulfate solution is the content of lithium ions in the solution obtained from the first stage of cyclic acid leaching;

[0134] Li leaching rate % is the leaching rate of lithium ions in the reduced battery powder;

[0135] Alkali room contains SO4 2- (g / L) is the sulfate content in the lithium hydroxide solution enriched in the alkali chamber after the purified lithium sulfate solution is electrolyzed by the bipolar membrane electrodialysis system;

[0136] Nanofiltration clear liquid contains SO4 2- (g / L) is the sulfate content of the lithium hydroxide solution enriched in the alkali chamber after multi-stage nanofiltration;

[0137] SO4 2- The retention rate % is the retention rate of lithium hydroxide solution after multi-stage nanofiltration;

[0138] The lithium hydroxide crystallization rate (%) is the crystallization rate of the lithium hydroxide solution after multi-stage nanofiltration.

[0139] The lithium hydroxide obtained in Examples 1-8 all complies with the national standard GB / T 26008-2020.

[0140] Comparative Example 1

[0141] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0142] 600g of retired ternary lithium-ion battery powder was mixed with 60g of glucose and subjected to a two-stage high-temperature reduction under a nitrogen atmosphere. The first stage was at 350°C for 2 hours, and the second stage was at 650°C for 3 hours. This yielded a reduced battery powder in which nickel, cobalt, and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate. 500g of the reduced battery powder, containing 4.4wt% lithium by mass and 1500g of pure water at a liquid-to-solid ratio of 3 / 1, was added. Oxalic acid (an organic acid) was then added at a molar ratio of oxalate to lithium ions of 1.1:2 for acid leaching.

[0143] Comparative Example 2

[0144] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0145] 600g of retired ternary lithium-ion battery powder was mixed with 60g of glucose and directly reduced at 650°C for 3 hours under a nitrogen atmosphere to obtain reduced battery powder, in which nickel, cobalt, and manganese were precipitated as metal elements or oxides, and lithium was precipitated as lithium carbonate. 500g of reduced battery powder, with a lithium mass fraction of 3.8wt%, was added to 1500g of pure water at a liquid-to-solid ratio of 3 / 1. Sulfuric acid was added at a molar ratio of sulfate to lithium ions of 1.1:2 for primary leaching. The resulting residue was filtered and a certain amount of sulfuric acid was added for secondary leaching. The secondary leachate was used in a circulating leaching process, resulting in a leachate primarily consisting of lithium sulfate.

[0146] Comparative Example 3

[0147] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0148] 600g of retired ternary lithium-ion battery powder was mixed with 60g of carbon powder and directly subjected to high-temperature reduction at 650°C for 3 hours. Nickel, cobalt, and manganese precipitated as metals or oxides, and lithium precipitated as lithium carbonate. 500g of reduced battery powder, containing a 3.6wt% lithium mass fraction, was added to 1500g of pure water at a liquid-to-solid ratio of 3 / 1. Sulfuric acid was added at a sulfate to lithium ion molar ratio of 1.1:2 for a first-stage leaching. The resulting residue was filtered and then subjected to a second-stage leaching process with a predetermined amount of sulfuric acid. The second-stage leachate was used in a circulating leaching process, resulting in a leachate primarily consisting of lithium sulfate. The lithium sulfate solution flowed through a calcium and magnesium removal resin and then into a bipolar membrane electrodialysis system. The alkaline electrolysis chamber enriched the lithium hydroxide solution. The enriched lithium hydroxide solution in the alkaline chamber was subjected to two-stage nanofiltration to remove sulfate, and the clear solution was subjected to a single-stage evaporation and crystallization to produce battery-grade lithium hydroxide.

[0149] Comparative Example 4

[0150] A method for recovering lithium from retired lithium-ion batteries comprises the following specific steps:

[0151] 600g of retired ternary lithium-ion battery powder is reduced at 650°C in a reducing atmosphere (H2). Nickel, cobalt, and manganese are precipitated as metal elements or oxides, and lithium is precipitated as lithium carbonate. 500g of reduced battery powder is taken, wherein the mass fraction of Li is 3.6wt%. 1500g of pure water is added at a liquid-to-solid ratio of 3 / 1. Sulfuric acid is added at a molar ratio of sulfate to lithium ions of 1.1:2 for a first-stage leaching. The resulting residue is filtered and a certain amount of sulfuric acid is added for a second-stage leaching. The second-stage leachate is used for a circulating leaching process. The resulting leachate is mainly lithium sulfate. A certain amount of sodium hydroxide is added for causticization. The causticized solution is placed in a frozen reactor, causing the sodium sulfate to precipitate as Glauber's salt at a certain temperature. The lithium sulfate solution is separated and subjected to a two-step evaporation crystallization to produce battery-grade lithium hydroxide.

[0152] The process data for lithium recovery from retired lithium-ion batteries in Comparative Examples 1 to 4 were calculated and listed as shown in Table 2.

[0153] Table 2 Process data for treating retired lithium-ion batteries in other processes

[0154]

[0155] Different from Example 1, the leaching acid in Comparative Example 1 was oxalic acid. Compared with sulfuric acid leaching, the Li leaching rate was nearly 10% lower.

[0156] Different from Example 1, in Comparative Example 2, the low-temperature roasting operation was not carried out, and high-temperature reduction was directly carried out. During this process, due to the relatively large size of the amorphous carbon particles formed, the reduction effect was worse than that of nanoscale amorphous carbon, resulting in a lower lithium concentration during the leaching process and a decrease in the lithium leaching rate.

[0157] Different from Example 1, in Comparative Example 3, the reducing agent was traditional carbon powder instead of glucose, and the nitrogen atmosphere protection was not used during the reduction process. The results showed that the Li leaching rate was nearly 10% lower with traditional carbon powder reduction than with glucose reduction.

[0158] Different from Example 1, in Comparative Example 4, the reduction was carried out under a reducing hydrogen atmosphere, and the bipolar membrane and nanofiltration system were not used. The freeze causticization process was directly used. The results showed that the lithium hydroxide crystallization rate was less than 70%.

[0159] The above-described embodiments only represent several implementation manners of the present disclosure. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several modifications and improvements can still be made, and these all belong to the protection scope of the present disclosure.

Claims

1. A method for recovering lithium from retired lithium-ion batteries, characterized in that, It includes the following steps: Reduction: A reducing agent is mixed into the retired ternary lithium-ion battery powder, and then it is placed under an inert atmosphere for two-stage reduction. The temperature of the first stage is 200 - 500 °C, and the duration is 1 - 3 h. The temperature of the second stage is 500 - 650 °C, and the duration is 2 - 4 h to obtain the reduced battery powder; Initial acid leaching: Part of the reduced battery powder is added to sulfuric acid, and the initial leachate and the initial leaching residue are obtained by filtration; Circulating acid leaching: First stage of circulating acid leaching: Another part of the reduced battery powder is added to a sulfate solution, and a lithium sulfate solution and the first-stage circulating leaching residue are obtained by filtration; Second stage of circulating acid leaching: The first-stage circulating leaching residue is added to sulfuric acid, and the second-stage circulating leachate and the nickel-cobalt-manganese residue are obtained by filtration; The reducing agent includes carbon or carbide; The sulfate solution is at least one of the initial leachate or the second-stage circulating leachate; the amount of sulfate in the first stage of circulating acid leaching is added according to the molar ratio of sulfate radical to lithium ion of (1 - 1.5):2; The lithium sulfate solution flows into the calcium and magnesium removal resin to obtain a purified lithium sulfate solution; The purified lithium sulfate solution is electrolyzed to obtain recycled sulfuric acid and a lithium hydroxide solution; The lithium hydroxide solution is nanofiltrated through a nanofiltration membrane system to obtain a purified lithium hydroxide solution; The purified lithium hydroxide solution is evaporated and crystallized to obtain battery-grade lithium hydroxide and the evaporation mother liquor.

2. The method for recycling lithium from retired lithium-ion batteries according to claim 1, characterized in that, The amount of sulfuric acid in the initial acid leaching is added according to the molar ratio of sulfate radical to lithium ion of (1 - 1.5):1; the amount of sulfuric acid in the second stage of circulating acid leaching is added according to the molar ratio of sulfate radical to lithium ion of (1 - 1.5):

2.

3. The method for recycling lithium from retired lithium-ion batteries according to claim 2, characterized in that, The first stage of circulating acid leaching and the second stage of circulating acid leaching are performed multiple times.

4. The method for recycling lithium from retired lithium-ion batteries according to claim 1, characterized in that, The reducing agent is at least one of wood chips, straw, sucrose, fructose, maltose, lactose, starch, and glucose.

5. The method for recovering lithium from retired lithium-ion batteries according to claim 1, wherein The dosage of the reducing agent is 5 - 30 wt% of the retired ternary lithium-ion battery powder.

6. The method for recovering lithium from retired lithium-ion batteries according to claim 1, wherein When the reduced battery powder is subjected to initial acid leaching and circulating acid leaching, the sulfuric acid is concentrated sulfuric acid, and pure water needs to be added before adding the concentrated sulfuric acid. The mass ratio of the pure water to the reduced battery powder, i.e., the liquid-solid ratio, is 3:1 - 10:

1.

7. The method for recovering lithium from retired lithium-ion batteries according to claim 1, wherein The sulfuric acid includes the recycled sulfuric acid.

8. The method for recycling lithium from retired lithium-ion batteries according to claim 1, wherein The nanofiltration membrane system is at least two-stage.

9. The method for recovering lithium from retired lithium-ion batteries according to claim 1, characterized in that, When performing the second stage of circulating acid leaching, the evaporation mother liquor is also added.

10. A method for recovering lithium from retired lithium-ion batteries according to claim 1, characterized in that, The leaching time for the initial acid leaching, the first stage of circulating acid leaching, and the second stage of circulating acid leaching is 1 - 2 h.

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