Method for separating and recycling valuable metal elements from waste lithium ion battery and regenerating positive electrode material

Abstract

The invention belongs to the technical field of recycling of electronic waste lithium ion batteries, and particularly relates to a method for separating and recycling valuable metal elements from waste lithium ion batteries and regenerating a positive electrode material. The invention provides a method which innovatively combines a deep eutectic solvent and mechanochemical activation and is used for efficiently separating and recycling valuable metal elements from waste lithium ion batteries and regenerating a positive electrode material. According to the method, efficient leaching of the waste positive electrode material and effective separation of valuable metal elements of lithium, nickel, cobalt and manganese are achieved through the synergistic effect of high dissolving capacity of the eutectic solvent and mechanochemical activation. The mild and efficient method is adopted, the problems that a deep eutectic solvent is complex to prepare and difficult to store, the leaching condition of a positive electrode material is harsh, and the consumption of a metal recovery reagent is large are solved, and high-selectivity leaching of lithium ions and separation and recovery of valuable metal elements of nickel, cobalt and manganese are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling electronic waste lithium-ion batteries, and more specifically, relates to a method for separating and recycling valuable metal elements from waste lithium-ion batteries and regenerating positive electrode materials. Background Art

[0002] In recent decades, with the rapid popularization of new energy vehicles and the wide application of portable electronic devices, the demand and capacity of energy storage batteries have grown rapidly. Among them, lithium-ion batteries dominate the market due to their unique advantages such as light weight, small size, long cycle life, high energy density and low self-discharge rate. It is predicted that by 2030, at least 145 million electric vehicles powered by lithium-ion batteries will be on the road. However, lithium-ion batteries cannot be recycled indefinitely. During multiple charging and discharging processes, the battery specific capacity gradually decreases until it reaches the scrap standard. Waste lithium-ion batteries are hazardous wastes. Unlike ordinary urban garbage, they can be disposed of by simple unified incineration or landfill. This is mainly because waste lithium-ion batteries contain a large amount of organic electrolytes and heavy metal ions. Random disposal will cause water and soil pollution, cause serious damage to the ecological environment, and even ultimately endanger human health. At the same time, waste lithium-ion batteries have high value-added resource attributes. Several metal elements including lithium, cobalt, nickel and copper in waste lithium-ion batteries are identified as expensive strategic resources. The efficient collection, recycling and reasonable disposal of a large number of waste lithium-ion batteries generated by effective recycling are necessary conditions for solving the problems of resource shortages and environmental hazards.

[0003] Direct regeneration, pyrometallurgy and hydrometallurgy are currently the most commonly used methods for recovering metals from waste lithium-ion batteries. The direct regeneration method has a short reaction process, but the process applicability is poor, and the quality of the regenerated product is not high, which limits its development; the pyrometallurgical process has simple pretreatment steps and is convenient for industrial application, but the process involved has high equipment requirements, high energy consumption, is not environmentally friendly, and has a large amount of lithium loss. Hydrometallurgy is currently the mainstream method for laboratory research and industrial application. It dissolves metal ions into a solution at a lower temperature, and recovers the valuable metals in the solution through further separation and purification. It has high recovery efficiency and low energy consumption. However, the multi-step separation process is still complicated, and the use of a large number of strong acid and alkali leaching agents and extractants inevitably causes a large amount of waste liquid and harmful gas emissions, and the equipment has high acid resistance requirements. In response to the above problems of wet recovery, researchers are also constantly exploring new and more environmentally friendly leaching agents and optimizing leaching processes, such as using more environmentally friendly organic acid leaching, applying ionic liquids and low eutectic solvents to the field of waste lithium battery recovery, etc. However, the following problems still exist: low eutectic solvents are difficult to store and need to be configured on site; valuable metal leaching often needs to be carried out under high temperature and high pressure, which is not conducive to energy conservation and environmental protection; in order to obtain transition metal salts of higher purity, a series of complex precipitation and extraction operations are usually adopted, the price of the extractant is expensive, and the impurities introduced in the leaching process complicate the purification process and produce a large amount of wastewater and waste residue. A large amount of lithium metal is lost in this cumbersome valuable metal extraction process, resulting in great waste. The current selective lithium extraction process reduces the waste of lithium, but ignores the recovery of other valuable metals. In summary, it is of great significance to develop a green leaching agent and recovery process to achieve low-cost and effective green recovery of waste ternary lithium-ion batteries, efficiently and selectively recover lithium, and make full use of the residues containing a large amount of heavy metals (e.g., nickel, cobalt, and manganese) generated after the recovery of lithium. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a method for selectively separating and recovering lithium salts, nickel, cobalt and manganese valuable metal elements and regenerating lithium ion battery positive electrode materials from waste lithium ion batteries, so as to solve the technical problems of the prior art in recycling waste lithium ion battery positive electrode materials, such as the large number of required reagents, complex recycling process, poor lithium recovery selectivity and low added value of recycled materials.

[0005] To achieve the above object, the present invention provides a method for separating and recovering valuable metal elements from waste lithium-ion batteries, comprising the following steps:

[0006] (1) Separating waste positive electrode materials from waste lithium-ion batteries;

[0007] (2) mixing the waste positive electrode material obtained in step (1) with a leaching agent and then ball milling to obtain a reaction solution; the leaching agent comprises a hydrogen bond donor and a hydrogen bond acceptor that can be used to form a deep eutectic solvent, wherein the hydrogen bond donor is an organic acid, and the hydrogen bond acceptor is a quaternary ammonium salt or an amine compound;

[0008] (3) The reaction solution of step (2) is transferred out with deionized water, and a water leaching reaction is carried out to convert the nickel, cobalt and manganese metal elements in the reaction solution into a precipitate. After the water leaching reaction is completed, the solid-liquid separation is carried out, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

[0009] Preferably, the waste positive electrode material is a waste ternary positive electrode material and / or a waste binary positive electrode material, and the waste positive electrode material is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide and nickel cobalt manganese oxide.

[0010] Preferably, the hydrogen bond donor in step (2) is one or more of oxalic acid, lactic acid and citric acid; the hydrogen bond acceptor is one or more of choline chloride, betaine hydrochloride and guanidine hydrochloride;

[0011] The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(0.5-2), more preferably 1:(1-1.5); the mass ratio of the waste positive electrode material to the leaching agent is 1:(3-30).

[0012] Preferably, the ball-to-material ratio in the ball milling process of step (2) is (10-100):1, the rotation speed is 100rpm-1000rpm, and the time is 30min-240min.

[0013] Preferably, in the water leaching reaction described in step (3), the mass ratio of deionized water to the leaching agent is 20-100:1, and the water leaching time is 0.5h-20h.

[0014] Preferably, the method further comprises the following step of regenerating and reusing the deep eutectic solvent:

[0015] (4) evaporating the leaching solution containing lithium metal ions to remove water to obtain a regenerated deep eutectic solvent;

[0016] (5) Separating waste positive electrode materials from waste lithium-ion batteries;

[0017] (6) using the regenerated low eutectic solvent of step (4) in a new round of waste positive electrode material regeneration process: mixing with the waste positive electrode material obtained in step (5) and then ball milling to obtain a reaction solution;

[0018] (7) The reaction solution of step (6) is transferred out with deionized water, and subjected to water leaching reaction, so that the nickel, cobalt and manganese metal elements in the reaction solution are fully converted into precipitates. After the water leaching reaction is completed, the solid-liquid separation is performed, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

[0019] According to another aspect of the present invention, a method for regenerating anode materials of lithium-ion batteries based on the method described is provided, comprising the following steps:

[0020] S1: Separating a lithium salt from the leaching solution containing lithium metal ions; the lithium salt is lithium carbonate;

[0021] S2: Determine the content of the metal element in the solid phase, the metal element is the metal element contained in the waste positive electrode material, which is one or more of nickel, cobalt and manganese, and add an appropriate amount of one or more of nickel compounds, cobalt compounds and manganese compounds to the target precursor ratio according to the metal element ratio in the target regenerated positive electrode material;

[0022] S3: The lithium salt obtained in step S1, the target precursor in step S2, and the lithium source required to be supplemented according to the target regenerated positive electrode material element ratio are mixed evenly, and sintered in an air atmosphere to obtain a regenerated lithium-ion battery positive electrode material.

[0023] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0024] (1) The present invention proposes a method for selectively separating and recovering lithium and valuable metals from waste lithium-ion batteries. For the first time, a low eutectic solvent is combined with ball milling technology to achieve efficient and selective leaching of waste lithium battery positive electrode materials. In addition, the water leaching process is innovatively used to achieve spontaneous separation of lithium and other metals, simplifying the subsequent separation process. First, waste binary or ternary lithium battery positive electrode materials are separated from waste lithium-ion batteries, and the strong mechanochemical force of ball milling is used to provide energy to reduce the activation energy of dissolution of the positive electrode materials. The leaching agent added during the ball milling process is a composite leaching agent that can form a low eutectic solvent. The composite leaching agent can completely destroy the structure of the waste positive electrode materials and achieve complete leaching of valuable metals. The metal lithium ions in the waste positive electrode materials are leached first, and the strong reducing property of organic acid hydrogen bond donors is used to reduce the high-valent nickel, cobalt, and manganese metal elements to low-valent states that are easier to complex with low-eutectic solvents. By simply adding deionized water, the organic acid radicals are ionized to form complex precipitation with the valuable metal ions, and the lithium metal ions are retained in the solution, thereby achieving efficient leaching and separation of metal ions. The method of the present invention solves the problems of the existing recovery technology with many types of additives, low metal ion recovery rate, poor selectivity, harsh leaching reaction conditions, and easy secondary pollution. The leaching agent of this method is simple to prepare, green and efficient, easy to biodegrade, non-corrosive, good in circulation, simple in process operation, and eliminates the step of configuring the leaching agent low-eutectic solvent, avoiding the problem of difficult storage of the low-eutectic solvent, and shortening the process flow.

[0025] (2) The present invention develops an in-situ preparation and recycling technology for low eutectic solvents, solving the problem of difficult storage of low eutectic solvents. The low eutectic solvent in the separated leachate is restored to its hydrogen bond structure and function by simply evaporating water, and is put into a new cycle as a leaching agent to dissolve the waste ternary lithium-ion battery positive electrode material, so that lithium metal ions are self-enriched in the process of step-by-step circulation. In this method, the grinding ball and the material collide, squeeze, shear and rub to induce physical changes and chemical reactions. The reaction system is at room temperature, avoiding the harsh reaction conditions of high temperature and high pressure. The hydrogen bond donor organic acid in the low eutectic solvent of the leaching agent of this method can be used as an acidic hydrogen proton provider, a reducing agent and a coprecipitant at the same time, so as to achieve the separation of mixed waste lithium-ion batteries, avoid multi-step extraction and separation of metal ions, reduce the loss and waste of metal resources, and achieve the purpose of selective recovery and concentration of lithium ions. This method has the advantages of high efficiency, environmental protection, low cost, short process flow, and high quality of recovered products.

[0026] (3) Mechanochemical technology is an efficient and environmentally friendly processing technology. The grinding ball and the material collide, squeeze, shear and rub to induce the occurrence of physical and chemical reactions. From the perspective of collision theory, the surface of the solid material is broken under the action of mechanical force, the crystal structure is cracked, the surface chemical bonds are broken, and a new active surface is generated. At the same time, under continuous impact, the material structure collapses and the internal instability increases sharply, so that a series of reactions that cannot be carried out at normal temperature and pressure can occur. The present invention adopts ball milling leaching to avoid the high temperature and high pressure processing environment and has no safety hazards. In the preferred embodiment, an environmentally friendly green solvent oxalic acid-based low eutectic solvent is used as a leaching agent. Due to the special properties of the hydrogen bond donor oxalic acid, nickel, cobalt and manganese are co-precipitated and recovered, and the precious lithium element is concentrated and enriched in the cycle. The low eutectic solvent is recycled many times; each step cooperates with each other to achieve a short-process green treatment of waste lithium-ion battery positive electrode materials. The process flow is simple, no excess wastewater is generated, and the reagent and energy consumption is small. Most of the metals in the ternary positive electrode material regenerated by the present invention are derived from lithium, nickel, cobalt and manganese elements recovered from waste ternary lithium-ion batteries, thereby achieving full resource utilization of waste.

[0027] (4) The present invention preferably has a ball-to-material ratio of (10-100): 1, a rotation speed of 600rpm-1000rpm, and a time of 90min-150min during the ball milling process. Ball milling with a sufficiently high ball-to-material ratio and rotation speed provides sufficient energy for the plastic deformation of the positive electrode material, the stress and strain within the molecule, and provides sufficient energy for the collision and friction between the raw materials in the mechanochemical reaction. The increase in the ball-to-material ratio and rotation speed is conducive to the increase in the rate of the mechanochemical reaction. A sufficiently long ball milling time can ensure that the mechanochemical reaction is carried out thoroughly at a certain reaction rate. Taking into account the energy consumption and treatment effect of ball milling, the above ball-to-material ratio, rotation speed, and time parameter limit ranges are selected.

[0028] (5) The present invention establishes a closed-loop recycling system from waste batteries to regenerated positive electrode materials, which fully recovers all elements in the positive electrode materials of waste lithium-ion batteries, thereby improving resource utilization efficiency. The recovered nickel salt, cobalt salt and manganese salt mixture and lithium salt are used to prepare a ternary positive electrode material with excellent performance through a two-stage solid-phase sintering method.

[0029] Figure 1 A flow chart of a method for selectively recovering lithium salts from waste lithium-ion battery positive electrode materials and preparing ternary positive electrode materials provided by the present invention.

[0030] Figure 2 It is the Fourier transform infrared (FTIR) spectrum of the oxalic acid-based deep eutectic solvent in Examples 1-7 and Comparative Examples 1-2.

[0031] Figure 3This is the X-ray diffraction (XRD) diagram of the precipitate after leaching of the waste lithium-ion battery positive electrode material in Example 1.

[0032] Figure 4 This is the X-ray diffraction (XRD) pattern of the lithium carbonate recovered in Example 1.

[0033] Figure 5 This is a scanning electron microscope (SEM) image of the precipitate after leaching of the waste lithium-ion battery positive electrode material in Example 1.

[0034] Figure 6 This is a comparison chart of the Fourier transform infrared (FTIR) spectra of the deep eutectic solvent regenerated by evaporating excess water from the leachate after water immersion in Example 5 and the fresh deep eutectic solvent.

[0035] Figure 7 It is a comparison chart of the leaching rates of lithium, nickel, cobalt, manganese, iron and phosphorus elements and lithium ion selectivity under different reaction conditions of Examples 1 to 8.

[0036] Figure 8 This is a high-resolution X-ray photoelectron spectroscopy (XPS) diagram of lithium, nickel, cobalt and manganese elements in Example 1.

[0037] Fig. 9 FTIR spectra of the original material and the precipitate after leaching before and after the ball milling leaching and water leaching reaction of the waste lithium-ion battery positive electrode material in Example 1.

[0038] Fig.10 This is the X-ray diffraction (XRD) pattern of the ternary positive electrode material prepared in Example 1.

[0039] Fig.11 Scanning electron microscope (SEM) images of the ternary positive electrode materials prepared in Example 1 and Example 2.

[0040] Fig.12 It is a comparison chart of the leaching rates of lithium, nickel, cobalt and manganese elements and lithium selectivity under different reaction systems of Example 1 and Comparative Examples 1 to 6.

[0041] Fig.13 It is a comparison chart of the leaching rates of lithium, nickel, cobalt and manganese elements and lithium selectivity under different reaction systems of Example 1 and Comparative Examples 7 to 9.

[0042] Fig.14 The discharge specific capacity curve of the ternary positive electrode materials prepared in Examples 1, 2 and 5 after 100 cycles at a 1C rate. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0044] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0045] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0046] In the present invention, unless otherwise specified and / or described, all numerical values ​​involving the amounts of components are "parts by weight" from beginning to end. The process parameters in the following examples without specifying specific conditions are usually based on conventional conditions.

[0047] The present invention provides a method for separating and recovering valuable metal elements from waste lithium-ion batteries, comprising the following steps:

[0048] (1) Separating waste positive electrode materials from waste lithium-ion batteries;

[0049] (2) mixing the waste positive electrode material obtained in step (1) with a leaching agent and then ball milling to obtain a reaction solution; the leaching agent comprises a hydrogen bond donor and a hydrogen bond acceptor that can be used to form a deep eutectic solvent, wherein the hydrogen bond donor is an organic acid and the hydrogen bond acceptor is a quaternary ammonium salt or an amine compound;

[0050] (3) The reaction solution of step (2) is transferred out with deionized water, and a water leaching reaction is carried out to fully convert the nickel, cobalt and manganese metal elements in the reaction solution into precipitates. After the water leaching reaction is completed, the solid-liquid separation is carried out, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

[0051] The waste positive electrode material of the present invention can be a waste ternary positive electrode material and / or a waste binary positive electrode material, and the waste positive electrode material is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide and lithium nickel cobalt manganese oxide. It is found in experiments that the method of the present invention is particularly suitable for lithium cobalt oxide binary positive electrode material and lithium nickel cobalt manganese oxide ternary positive electrode material.

[0052] In some embodiments, step (1) of separating and recovering waste positive electrode materials from waste ternary lithium batteries specifically comprises the following steps: discharging the waste lithium-ion batteries, and then disassembling and stripping off the parts other than the positive electrode materials of the lithium-ion batteries to obtain waste positive electrode materials.

[0053] In some embodiments, the disassembly can be manual disassembly pretreatment or integrated industrial equipment disassembly pretreatment. Manual disassembly pretreatment generally includes manual disassembly, crushing, alkali treatment, calcination and other steps; integrated industrial equipment pretreatment generally includes mechanical crushing, magnetic separation, air separation, calcination and other steps.

[0054] In some embodiments, the disassembly in the manual pretreatment is specifically as follows: the waste lithium-ion battery is connected to the discharger for discharge, and after the discharge is completed, the battery shell is manually cut open, the positive and negative pole ears are removed, and then the positive electrode sheet, negative electrode sheet and separator are collected separately. Crushing is as follows: using scissors to cut the positive electrode sheet containing aluminum foil into pieces of about 1cm×1cm: mixing and stirring the crushed positive electrode sheet with 2mol / L NaOH or KOH, and waiting until no bubbles are generated in the reaction solution, indicating that the aluminum foil has been basically dissolved, filtering the solution and washing it with deionized water for several times, and the obtained black solid powder is placed in a 60℃ oven for drying, and calcination is specifically as follows: calcining the black solid powder at 550-700℃ for 3-5h to remove the binder; finally, the waste ternary lithium battery positive electrode material is obtained.

[0055] In other embodiments, waste positive electrode materials are obtained by comprehensive physical sorting of large-scale production through mechanical crushing, air separation, magnetic separation and other equipment. Specifically, the waste lithium-ion battery is connected to the discharger for discharge, and after the discharge is completed, it is put into the lithium battery crushing and sorting integrated equipment. The battery is subjected to a coarse crushing and sorting device to obtain a mixture containing positive electrode materials, negative electrode graphite, iron sheets, aluminum foil and copper foil. The negative electrode graphite and other non-metallic materials are separated by an air separation device in turn, and copper and aluminum are separated by a heating device, and then a black solid powder is obtained. Finally, the black solid powder is placed in a muffle furnace and calcined at 550-700°C for 3-5h to obtain the waste ternary lithium battery positive electrode material.

[0056] In a preferred embodiment, the hydrogen bond donor in step (2) is oxalic acid, lactic acid, citric acid, etc.; the hydrogen bond acceptor is choline chloride, betaine hydrochloride, guanidine hydrochloride, etc.; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(0.5-2), preferably 1:(1-1.5), and the mass ratio of the waste positive electrode material to the leaching agent is 1:(3-30), more preferably 1:(10-30).

[0057] The melting point of the low eutectic solvent is lower than that of the single component. At room temperature, some low eutectic solvents are prone to recrystallization and crystal precipitation, which will destroy the hydrogen bond structure and cause the problem of difficult storage. The present invention mixes the hydrogen bond donor and hydrogen bond acceptor that can form the low eutectic solvent with the waste positive electrode material for ball milling, eliminating the step of pre-preparing the low eutectic solvent and cleverly avoiding the storage of the low eutectic solvent.

[0058] In some embodiments, the ball-to-material ratio in the ball milling process of step (2) is (10-100):1, preferably (10-40):1; the rotation speed is 100rpm-1000rpm, preferably 600rpm-800rpm; the time is 30min-240min, preferably 90min-150min.

[0059] In some embodiments, the grinding balls and the ball mill used in the ball milling process are independently made of stainless steel, cast iron, zirconia, agate, corundum or polytetrafluoroethylene.

[0060] Taking hydrogen bond donor oxalic acid and hydrogen bond acceptor choline chloride as examples, in the ball milling mechanochemical reaction process of the present invention, hydrogen bond donor oxalic acid and hydrogen bond acceptor choline chloride are ground by ball milling beads to quickly form a liquid low eutectic solvent containing hydrogen bonds. Under the mechanochemical action, the crystal structure of the positive electrode material is destroyed, and the reduced particle size and increased specific surface area of ​​the positive electrode material provide more action points for hydrogen bond attack; the hydrogen protons in oxalic acid first replace the lithium in lithium nickel cobalt manganese oxide, so that the positive electrode material lattice collapses further, releasing valuable metal ions, which are exposed to the oxalate radical with strong reducing property, and then undergo redox reaction with the oxalate radical, and the high-valent metal ions are reduced to be more easily reacted with Cl in the low eutectic solvent. - Complexed low-valent metal ions, with Cl - Combined into a complex in the solution, generating carbon dioxide. - The valuable metal ions compete for new complexation to generate nickel oxalate, manganese oxalate and cobalt oxalate flocculent precipitates, which enter the solid phase, while lithium ions remain in the liquid phase, thus achieving the selective leaching of lithium ions in the positive electrode materials of waste lithium-ion batteries and the recovery of valuable metal ions of nickel, cobalt and manganese.

[0061] During the ball milling reaction process of the present invention, strong mechanical force destroys the structure of waste positive electrode materials, and efficiently leaches metal lithium, nickel, cobalt, and manganese ions in the positive electrode materials. At the same time, it is speculated that the strong reducing property of oxalic acid reduces high-valent metal ions to low-valent states and forms a blue transparent complex with chloride ions; after ionization, oxalate forms a coprecipitate with nickel, cobalt, and manganese metal ions. The solubility of lithium ions and oxalate complexes is relatively large and easily soluble in the solution, thereby achieving efficient leaching and separation of metal ions. This method does not require additional coprecipitants, can achieve the separation of mixed waste lithium-ion batteries, and achieve the purpose of selective recovery of lithium ions.

[0062] Step (3) transfers the reaction liquid after ball milling with deionized water, that is, the reaction liquid obtained by ball milling, the ball milling beads, and the reaction liquid adhered to the wall of the ball milling tank are washed with deionized water and transferred to a container, and deionized water is added or not added as needed for leaching, and the water immersion is sufficient time to fully precipitate the nickel, cobalt and manganese metals. In some embodiments, the mass ratio of deionized water to the leaching agent in the water immersion reaction described in step (3) is 20-100:1, preferably 30-50:1; the water immersion time is 0.5h-20h, preferably 2h-10h. The solid-liquid separation in step (3) is a conventional solid-liquid separation method such as atmospheric pressure filtration or low-pressure suction filtration.

[0063] In some other embodiments, the low eutectic solvent in the lithium ion leachate obtained by the primary ball milling separation is reused, for example, the following regeneration and reuse steps may be included:

[0064] (4) evaporating the leaching solution containing lithium metal ions to remove water to obtain a regenerated deep eutectic solvent;

[0065] (5) Separating waste positive electrode materials from waste lithium-ion batteries;

[0066] (6) mixing the waste positive electrode material obtained in step (5) with the regenerated low eutectic solvent in step (4) and then ball milling to obtain a reaction solution;

[0067] (7) The reaction solution of step (6) is transferred out with deionized water, and subjected to water leaching reaction, so that the nickel, cobalt and manganese metal elements in the reaction solution are fully converted into precipitates. After the water leaching reaction is completed, the solid-liquid separation is performed, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

[0068] During the recycling process of the low eutectic solvent, a self-separated mixture of valuable metal organic acid salts is obtained, and lithium ions are gradually concentrated during the recycling process. After the cycle is completed, the pH is adjusted, carbonate is added, and the lithium salt in the solution is recovered in the form of lithium carbonate.

[0069] After the present invention separates lithium from the valuable metals nickel, cobalt and manganese, it can also regenerate the positive electrode material of the lithium-ion battery, for example, it can include the following steps:

[0070] S1: Separating a lithium salt from the leaching solution containing lithium metal ions; the lithium salt is lithium carbonate;

[0071] S2: Determine the content of metal elements in the solid phase, where the metal elements are metal elements contained in the waste positive electrode material, which are one or more of nickel, cobalt and manganese. According to the ratio of metal elements in the target regenerated positive electrode material, add an appropriate amount of one or more of nickel compounds, cobalt compounds and manganese compounds to the target precursor ratio; here, the initial waste positive electrode material is a ternary positive electrode material, and the target regenerated positive electrode material can be the same ternary positive electrode material, or it can be a mono- or binary positive electrode material.

[0072] S3: The lithium salt obtained in step S1, the target precursor in step S2, and the lithium source required to be supplemented according to the target regenerated positive electrode material element ratio are mixed evenly, and sintered in an air atmosphere to obtain a regenerated lithium-ion battery positive electrode material.

[0073] In some embodiments, step S1 adjusts the pH of the leaching solution containing lithium metal ions to 9-10 with ammonia water and dilute hydrochloric acid, and recovers lithium carbonate after adding carbonate.

[0074] In some embodiments, the nickel compound in step S2 is at least one of nickel oxalate, nickel acetate, and nickel oxide, the cobalt compound is at least one of cobalt oxalate, cobalt acetate, and cobalt chloride, and the manganese compound is at least one of manganous oxalate, manganese dioxide, and manganous carbonate;

[0075] When the target regenerated positive electrode material is lithium nickel cobalt manganese oxide, the ratio of the amount of nickel source, cobalt source and manganese source in the waste ternary positive electrode material is feasible within a large range. When the ternary positive electrode material is finally prepared, it can be supplemented according to the respective contents in the solid phase and liquid phase after solid-liquid separation, without affecting the recovery of lithium ions and nickel salts, cobalt salts and manganese salts, nor affecting the preparation of ternary positive electrode materials. The mass ratio of the three is usually set to 1:1:1, 5:3:2, 5:2:3, 6:2:2 or 8:1:1. The molar ratio of the valuable metal elements to the lithium element in the target precursor is 1:1.05 or 1:1.1, and the valuable metal elements include nickel, cobalt and manganese.

[0076] In some embodiments, the sintering in step S3 includes the following sub-steps: firstly pre-calcining in an air atmosphere to preliminarily shape the mixture to obtain a pre-calcined product; and then secondarily calcining the obtained pre-calcined product in an air atmosphere to obtain a regenerated positive electrode material.

[0077] In a preferred embodiment, the pre-calcination temperature is 300-600° C., and the pre-calcination time is 2-8 hours; the secondary calcination temperature is 800-1000° C., and the calcination time is 5-15 hours.

[0078] The present invention proposes a method for recovering lithium, nickel, cobalt and manganese salts from waste lithium-ion batteries and preparing ternary positive electrode materials based on a mechanochemical method. Under the action of mechanical ball milling, a green and efficient low eutectic solvent formed by ball milling is used to realize the room temperature efficient leaching of metal ions in the ternary positive electrode material, and then the leached mixture is transferred to a beaker by simple water washing. After a period of water leaching, the transition metal ions in the leachate form metal salt precipitation and separate from the lithium ions in the solution. In the preferred embodiment, lithium self-enrichment and full utilization of the low eutectic solvent reagent are realized in multiple cycles. After enriching and concentrating lithium ions, the solution adjusts the pH, and lithium is recovered in the form of lithium carbonate, realizing the full recovery of metals in the positive electrode material and the selective recovery of lithium. No other impurity metal ions and inorganic ions are introduced during the treatment process. After the nickel oxalate cobalt manganese coprecipitation precursor is supplemented with lithium, it is ball milled and mixed, and roasted to obtain a regenerated ternary positive electrode material with excellent electrochemical properties. The present invention adopts a mild and efficient method to solve the problems of complex preparation of low eutectic solvents, difficult storage, harsh leaching conditions for positive electrode materials, large consumption of metal recovery reagents, etc., avoids secondary pollution of the environment, and has the advantages of low cost, simple process, easy availability of raw materials, easy process expansion, and industrialization.

[0079] The present invention does not require an additional coprecipitant to separate the valuable metals of waste lithium-ion batteries and achieve the purpose of selectively recovering lithium-ion metals, thereby reducing the process production cost and solving the problems of the existing technology for recovering waste lithium-ion battery positive electrode materials, such as the large number of required additives, complex operation process, harsh leaching reaction conditions, and low added value of regenerated positive electrode materials. At the same time, the present invention proposes a new method for selectively recovering lithium salts and regenerating positive electrode materials based on waste nickel-cobalt-manganese oxide lithium batteries. Through the method of the present invention, efficient recovery of lithium, nickel, cobalt, and manganese elements in waste lithium-ion battery positive electrode materials can be achieved, reducing resource waste and improving the comprehensive recovery rate of waste lithium-ion batteries. The method is simple in process flow, convenient in operation, and has high economic benefits and environmental friendliness.

[0080] The following are examples:

[0081] Example 1

[0082] This embodiment provides a method for preparing a ternary positive electrode material by ball milling and leaching a ternary positive electrode material using a choline chloride oxalate deep eutectic solvent, water leaching and co-precipitating nickel, cobalt and manganese metals, and selectively recovering lithium salts, comprising the following steps:

[0083] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0084] (2) 90g of ball milling beads, 0.15g of waste ternary cathode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) are added to a ball mill, and the ball milling reaction is carried out at 700rpm for 120min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and the leachate and leached precipitate are separated by suction filtration after 3h of water immersion. The filter residue is washed with deionized water and ethanol for many times, and the lithium-rich leachate (adjusting the pH to about 10 with ammonia water and dilute hydrochloric acid) uses sodium carbonate as a co-precipitant to recover lithium carbonate.

[0085] (3) ICP-OES was used to determine the leaching rate of metal elements, and the contents of nickel, cobalt and manganese metal elements in the complex precipitate were obtained. Appropriate amounts of nickel oxalate, cobalt oxalate and manganous oxalate were added to the precursor so that the molar ratio of nickel, cobalt and manganese in the precursor was 6:2:2.

[0086] (4) Lithium carbonate and a precursor are mixed in a molar ratio of lithium, nickel, cobalt and manganese of 1.05:0.6:0.2:0.2, and the mixture is ball-milled for 2 hours to mix evenly. The mixture is calcined at 500°C for 5 hours to obtain a pre-calcined product, and then calcined at 850°C for 10 hours to obtain a ternary positive electrode material.

[0087] (5) The lithium sheet was used as the negative electrode and the regenerated positive electrode material was assembled into a button half-cell. The battery test system was used to measure its cyclic charge and discharge performance at a rate of 1C (1C = 230 mAh / g). The initial discharge specific capacity was 155 mAh / g, and the capacity retention rate after 100 charge and discharge cycles was 86.9%.

[0088] Figure 2 The content of Example 1 proves the formation of hydrogen bonds. The results show that the stretching vibration peak of the hydroxyl group in the deep eutectic solvent changes from 3255 cm-1 of choline chloride to -1 and 3430cm of oxalic acid -1 Migrate to 3355cm -1 This may be due to Cl -The strong electronegativity and inductive effect of the OH group in the deep eutectic solvent indicate that the OH group participates in a more extensive hydrogen bonding network. The shift of the OH peak indicates that the hydrogen bonding strength of the OH group in the deep eutectic solvent is weaker than that in the pure components of oxalic acid and choline chloride, indicating the strengthening of intramolecular hydrogen bonding and the weakening of intermolecular hydrogen bonding. It is also observed that due to Cl - Under the influence of the strong electronegativity of -1 The blue shift to 1720 cm of the deep eutectic solvent -1 .

[0089] Figure 3 Example 1 is a leaching method using an oxalic acid-based low eutectic solvent as a leaching agent, and the XRD pattern of the precipitate after water leaching selectively precipitates metal elements. As can be seen from the figure, the main material components of the precipitate are NiC2O4·2H2O, CoC2O4·2H2O and MnC2O4·2H2O.

[0090] Figure 4 The content of Example 1 is that after ball milling leaching and water leaching selective precipitation using choline chloride oxalate low eutectic solvent as the leaching agent, the pH of the leachate is adjusted to about 10, and then sodium carbonate precipitant is added to precipitate the product, and its diffraction peak position and intensity are consistent with the lithium carbonate standard card, indicating that the recovered lithium carbonate has low impurity content and high purity.

[0091] Figure 5 Example 1 is a SEM image of the precipitate after ball milling leaching and water leaching selective precipitation using choline oxalate chloride low eutectic solvent as the leaching agent. It can be seen from the figure that the particle size of the precipitate is between 700 and 900 nm, among which the short rod-shaped particles are NiC2O4·2H2O, the needle-shaped particles are CoC2O4·2H2O, and the irregular ellipsoidal particles are MnC2O4·2H2O.

[0092] Figure 7 It can be seen that the leaching rates of nickel, cobalt and manganese ions in the leachate after water immersion in this embodiment are relatively low, all below 5%, while the leaching rate of lithium ions is 98%, which has high selectivity. The nickel, cobalt and manganese ions in the positive electrode material of the waste lithium-ion battery are selectively concentrated in the precipitate by the method of this embodiment, thereby achieving effective separation from the lithium ion metal.

[0093] Figure 8 The XPS high-resolution energy spectrum of lithium, nickel, cobalt, and manganese elements in the precipitate and the original material after the selective precipitation of metal elements by water leaching using an oxalic acid-based low eutectic solvent as the leaching agent in Example 1 is shown in the figure. As can be seen from the figure, after leaching, no characteristic peaks are found in the energy spectrum corresponding to lithium, indicating that the lithium element is selectively leached during the reaction after leaching, and Co2p 3 / 2 , Ni 2p 3 / 2 、Mn 2p3 / 2 The binding energies of the mixed valence states (+2, +3) of Ni, the high valence state (+3) of Co, and the high valence state (+4) of Mn were reduced to the low valence state of Co. 2+ 、Ni 2+ , Mn 2+ It then forms oxalate co-precipitation with oxalic acid in the solution.

[0094] Fig. 9 The FTIR spectra of the precipitate and the original material obtained by leaching metal ions using an oxalic acid-based deep eutectic solvent as a leaching agent in Example 1 are shown in FIG. 1 . It can be seen from the figure that the characteristic peak generated by the asymmetric stretching of transition metal oxides in the raw material is mainly at 576 cm -1 and 536cm -1 At 3410 cm -1 The peak at 1625 cm corresponds to the stretching vibration of OH. -1 The peak at 1350cm is due to the antisymmetric stretching vibration of COO. -1 The peak of COO symmetric stretching vibration is 1311 cm -1 The vibration peak at 20 cm corresponds to the CO bending vibration, proving the existence of oxalate. The frequency difference between the antisymmetric stretching vibration peak and the symmetric stretching vibration peak is more than 200 cm -1 , proving that the coordination mode between nickel, cobalt and manganese metal ions and carboxylates is monodentate.

[0095] Fig.10 This is the XRD of the regenerated nickel cobalt manganese oxide positive electrode material. The characteristic peak (003) of the regenerated positive electrode material is obvious in the figure, and the diffraction peaks (006) and (102), (108) and (110) are obviously split, which is completely consistent with the marked material card, indicating that the positive electrode material regenerated in Example 1 has a higher purity, a better structure, and less mixing.

[0096] Fig.11 This is a scanning electron microscope image of the ternary positive electrode material prepared in Example 1. From the image, it can be seen that the prepared ternary positive electrode material is approximately spherical, uniform in size, and has good particle growth, indicating that the material has good physical properties.

[0097] Example 2

[0098] This embodiment provides a method for preparing a ternary positive electrode material by ball milling and water leaching to self-separate nickel, cobalt and manganese salts and selectively recovering lithium salts using a choline chloride oxalate deep eutectic solvent, comprising the following steps:

[0099] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0100] (2) 90g of ball milling beads, 0.15g of waste ternary cathode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) are added to a ball mill, and the ball milling reaction is carried out at 650rpm for 150min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and the leachate and leached precipitate are separated by suction filtration after immersion for 3h. The coprecipitated product is washed with deionized water and ethanol for many times, and the lithium-rich leachate (adjusted to pH about 10 with ammonia water and dilute hydrochloric acid) uses sodium carbonate as a coprecipitant to recover lithium carbonate.

[0101] (3) ICP-OES was used to determine the leaching rate of metal elements, and the contents of nickel, cobalt and manganese metal elements in the complex precipitate were obtained. Appropriate amounts of nickel oxalate, cobalt oxalate and manganous oxalate were added to the precursor so that the molar ratio of nickel, cobalt and manganese in the precursor was 6:2:2.

[0102] (4) Lithium carbonate and a precursor are mixed in a molar ratio of lithium, nickel, cobalt and manganese of 1.05:0.6:0.2:0.2, and the mixture is ball-milled for 2 h to mix evenly. The mixture is calcined at 500 °C for 5 h to obtain a pre-calcined product, and then calcined at 850 °C for 12 h to obtain a ternary positive electrode material.

[0103] (5) The lithium sheet was used as the negative electrode and the regenerated positive electrode material was assembled into a button half-cell. The battery test system was used to measure its cyclic charge and discharge performance at a rate of 1C (1C = 230 mAh / g). The initial discharge specific capacity was 143 mAh / g, and the capacity retention rate after 100 charge and discharge cycles was 81.0%.

[0104] Fig.11 Example 2 in the content is a scanning electron microscope image of the ternary positive electrode material regenerated in this example. It can be seen from the figure that the regenerated ternary positive electrode material is approximately spherical, uniform in size, and has good particle growth, indicating that the material has good physical properties.

[0105] Example 3

[0106] This embodiment provides a method for self-separating nickel, cobalt and manganese salts by ball milling and water leaching using a choline oxalate chloride deep eutectic solvent and selectively recovering lithium salts, comprising the following steps:

[0107] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0108] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.55 g of choline chloride and 1.4 g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) were added to a ball mill and milled at 700 rpm for 240 min. After the reaction, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water. After immersion for 3 h, the leachate and the leached precipitate were separated by suction filtration, and the metal element concentration in the leachate was determined by ICP-OES to obtain the leaching rate.

[0109] Example 4

[0110] This embodiment provides a method for preparing a ternary positive electrode material by ball milling and water leaching to self-separate nickel, cobalt and manganese salts and selectively recovering lithium salts using a choline chloride oxalate deep eutectic solvent, comprising the following steps:

[0111] (1) The waste ternary lithium-ion battery is discharged by a discharger to a voltage of ≤2V, and then put into a lithium battery crushing and sorting integrated device. The battery is subjected to a coarse crushing and sorting device to obtain a mixture containing positive electrode materials, negative electrode graphite, iron sheets, aluminum foil and copper foil. The negative electrode graphite and other non-metallic materials are separated by an air separation device. The copper and aluminum are separated by a heating device to obtain a black solid powder. The black solid powder is calcined at 650°C for 3h to remove the binder; finally, the waste ternary lithium battery positive electrode material is obtained.

[0112] (2) 90g of ball milling beads, 0.20g of waste ternary cathode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:15) are added to a ball mill, and the ball milling reaction is carried out at 700rpm for 120min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and the leachate and the leached precipitate are separated by suction filtration after immersion for 3h. The filter residue is washed with deionized water and ethanol for many times, and the lithium-rich leachate (adjusting the pH to about 10 with ammonia water and dilute hydrochloric acid) uses sodium carbonate as a coprecipitant to recover lithium carbonate.

[0113] (3) ICP-OES was used to determine the leaching rate of metal elements, and the contents of nickel, cobalt and manganese metal elements in the complex precipitate were obtained. Appropriate amounts of nickel oxalate, cobalt oxalate and manganous oxalate were added to the precursor so that the molar ratio of nickel, cobalt and manganese in the precursor was 6:2:2.

[0114] (4) Lithium carbonate and a precursor are mixed in a molar ratio of lithium, nickel, cobalt and manganese of 1.1:0.6:0.2:0.2, and the mixture is ball-milled for 2 h to mix evenly. The mixture is calcined at 500 °C for 5 h to obtain a pre-calcined product, and then calcined at 850 °C for 10 h to obtain a ternary positive electrode material.

[0115] like Figure 7 As shown, this embodiment adopts industrial equipment disassembly and sorting, and the leaching rates of lithium, nickel, cobalt and manganese after leaching by the method of the present invention are 97.62%, 0.86%, 0.39% and 3.69% respectively, and the leaching selectivity is 95.19%. It can be seen that whether it is manual disassembly or industrial equipment disassembly and sorting for pretreatment, as long as the waste lithium ion batteries are pretreated in sequence to obtain waste lithium ion positive electrode materials, and the method of the present invention is used for leaching, the leaching rate is basically the same.

[0116] Example 5

[0117] This embodiment provides a method for preparing a ternary positive electrode material by ball milling and leaching a ternary positive electrode material with a recycled low eutectic solvent, water leaching and co-precipitation of nickel, cobalt and manganese metals, and selectively recovering lithium salts, such as Figure 1 As shown, the following steps are included:

[0118] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0119] (2) The lithium-rich leaching solution obtained in step (2) of Example 1 was placed in an oven at 120° C. for evaporation for 10 h to obtain a regenerated low eutectic solvent with dried water.

[0120] (3) 90 g of ball milling beads, 0.15 g of the waste ternary cathode material obtained in step (1) and the regenerated low eutectic solvent obtained in step (2) were added to a ball mill, and the ball milling reaction was carried out at 700 rpm for 120 min. After the reaction was completed, the reaction solution in the ball mill was washed into a beaker with 100 ml of deionized water, and the leaching solution and the leached co-precipitated product were separated by suction filtration after immersion for 3 h. The co-precipitated product was washed with deionized water and ethanol for multiple times, and the lithium-rich leaching solution (adjusted to pH 10 with ammonia water and dilute hydrochloric acid) used sodium carbonate as a co-precipitant to recover lithium carbonate.

[0121] (4) ICP-OES was used to determine the leaching rate of metal elements, and the contents of nickel, cobalt and manganese metal elements in the coprecipitated complex were obtained. Appropriate amounts of nickel oxalate, cobalt oxalate and manganese oxalate were added to the precursor so that the molar ratio of nickel, cobalt and manganese in the precursor was 6:2:2.

[0122] (5) Lithium carbonate and nickel cobalt manganese oxalate were adjusted to a molar ratio of lithium: nickel: cobalt: manganese of 1.05:0.6:0.2:0.2, and ball milled for 2 hours. The mixed mixture was calcined at 500°C for 5 hours to obtain a pre-calcined product, and then calcined at 850°C for 10 hours to obtain a ternary positive electrode material.

[0123] Figure 6 This shows that after evaporating excess water in this embodiment, the low eutectic solvent restores the original hydrogen bond structure. In this embodiment, the regenerated low eutectic solvent is used as a leaching agent to treat the positive electrode material. The leaching rate of Li reaches 96.59%, and nickel, cobalt and manganese are almost not leached. The leaching selectivity reaches more than 98%. This shows that the regenerated low eutectic solvent has good leaching performance, such as Figure 7 shown.

[0124] Fig.14 The battery charge and discharge cycle data of Examples 1, 2 and 5 show that after 100 cycles at 1C, the batteries in Examples 1, 2 and 5 all have a relatively high capacity retention rate.

[0125] Example 6

[0126] This embodiment uses the choline chloride oxalate deep eutectic solvent to perform ball milling and water leaching recovery, which includes the following steps:

[0127] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste lithium cobalt oxide battery positive electrode material is obtained.

[0128] (2) Add 90g of ball milling beads to a ball mill, add 0.15g of waste lithium cobalt oxide positive electrode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of positive electrode material to leaching agent is 1:20), and ball milling reaction is carried out at 700rpm for 120min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and after immersion for 3h, the leachate and the residue are separated by suction filtration, and the metal element concentration in the leachate is determined by ICP-OES to obtain the leaching rate.

[0129] The other conditions of this embodiment are the same as those of embodiment 1, the only difference being that the waste positive electrode material of waste lithium-ion batteries used in this embodiment is lithium cobalt oxide, while the other embodiments use nickel-cobalt-manganese ternary positive electrode materials. Figure 7 It can be seen that the leaching rate of lithium element in the leaching solution of this embodiment is relatively high, which is 98.76%; the leaching rate of cobalt element is relatively low, which may be because both lithium cobalt oxide and lithium nickel cobalt manganese oxide are layered structures. The layered structure of the positive electrode material is easily destroyed under ball milling in the low eutectic solvent. The leaching of lithium element accelerates the collapse of the structure. The cobalt element has a high valence state and is easily reduced by oxalic acid, and the divalent cobalt element has a strong binding ability with the chloride ions in the low eutectic solvent. The binding energy of cobalt and free oxalate in the solution after water immersion is stronger, and it is precipitated in the form of cobalt oxalate and separated from the lithium in the solution, so it has a higher lithium leaching rate and leaching selectivity.

[0130] Example 7

[0131] This embodiment uses the choline chloride oxalate deep eutectic solvent to perform ball milling and water leaching recovery, which includes the following steps:

[0132] (1) The waste lithium iron phosphate battery was discharged with a discharger until the voltage was ≤2V, and then the positive electrode sheet was manually disassembled and separated. The positive electrode sheet was cut into pieces of about 1cm×1cm, and the broken positive electrode sheet was mixed with 2mol / L NaOH and stirred until no bubbles were generated. The solution was filtered and washed with deionized water for multiple times. The obtained black solid powder was placed in a 60℃ oven for drying, and then acetone was added to the black solid powder at a mass ratio of 1:5. The positive electrode sheet was ball milled at a speed of 400r / min for 6h, and calcined at 600℃ for 4h in a nitrogen atmosphere to remove the binder; finally, the waste lithium iron phosphate positive electrode material was obtained.

[0133] (2) Add 90g of ball milling beads to a ball mill, add 0.15g of waste lithium iron phosphate positive electrode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of positive electrode material to leaching agent is 1:20), and ball milling reaction is carried out at 700rpm for 120min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and after immersion for 3h, the leachate and the leached precipitate are separated by suction filtration, and the metal element concentration in the leachate is determined by ICP-OES to obtain the leaching rate.

[0134] The other conditions of this embodiment are the same as those of embodiment 1, the only difference being that the waste positive electrode material of waste lithium-ion batteries used in this embodiment is lithium iron phosphate, while the other embodiments use a ternary positive electrode material of lithium nickel cobalt manganese oxide. Figure 7 It can be seen that the leaching rates of lithium, iron and phosphorus in the leaching solution of this embodiment are relatively high, which are 91.02%, 96.89% and 97.11% respectively. This indicates that most of lithium, iron and phosphorus are leached out after ball milling, but iron ions are not combined with oxalate to precipitate during water leaching. The reason may be that the strong force of ball milling and the hydrogen bond of the deep eutectic solvent can also play a good role in destroying the olivine crystal structure of lithium iron phosphate, but at room temperature, iron ions in lithium iron phosphate are difficult to combine with oxalate to form precipitates.

[0135] Example 8

[0136] This embodiment uses the choline chloride oxalate deep eutectic solvent to perform ball milling and water leaching recovery, which includes the following steps:

[0137] (1) The waste lithium manganese oxide battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying, and then acetone is added to the black solid powder at a mass ratio of 1:5. The positive electrode sheet is ball milled at a speed of 400 r / min for 6 hours, and calcined at 600°C for 4 hours in a nitrogen atmosphere to remove the binder; finally, the waste lithium manganese oxide positive electrode material is obtained.

[0138] (2) Add 90g of ball milling beads to a ball mill, add 0.15g of waste lithium manganese oxide positive electrode material, 1.55g of choline chloride and 1.4g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of positive electrode material to leaching agent is 1:20), and ball milling reaction is carried out at 700rpm for 120min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100ml of deionized water, and after immersion for 3h, the leachate and the leached precipitate are separated by suction filtration, and the metal element concentration in the leachate is determined by ICP-OES to obtain the leaching rate.

[0139] The other conditions of this embodiment are the same as those of embodiment 1, except that the positive electrode material of the waste lithium-ion battery used in this embodiment is lithium manganese oxide. Figure 7 It can be seen that the leaching rate of lithium ions in this embodiment is 72.24%, which is lower than that in Example 1, and the leaching rate of manganese ions is 22.15%, which is higher than the leaching rate of manganese in the nickel cobalt lithium manganate positive electrode material in Example 1. This indicates that most of the lithium is leached after ball milling, while most of the manganese ions are complexed with oxalate in the solution to form manganese oxalate complex precipitation. The reason may be that the spinel structure of lithium manganate is not conducive to the dissolution of lithium ions, the lithium ion leaching rate is relatively reduced, and there is no element that needs to be reduced in lithium manganate. The oxalic acid-based low eutectic solvent with strong reducing property has little effect on metal leaching. The reason for the high leaching rate of manganese ions and the low precipitation rate may be that the solubility product constant of manganese oxalate is large, and the dissolved manganese ions of lithium manganate are difficult to combine with oxalate to form a precipitate at room temperature.

[0140] Example 9

[0141] This example uses the choline chloride oxalate deep eutectic solvent recycled multiple times for ball milling and water leaching recovery to illustrate the effect of recycling the leaching agent on the recovery effect, including the following steps:

[0142] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0143] (2) The method in Example 5 was used to recycle the leaching agent for multiple times, and 0.15 g of waste ternary cathode material was added to a ball mill, and the ball milling reaction was carried out at 700 rpm for 120 min. After the reaction, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water, and the leachate and the residue were separated by filtration after 3 h of water immersion. After each cycle, the concentration of metal elements in the leachate was determined by ICP-OES to obtain the leaching rate.

[0144] Table 1 Effect of the number of times the leaching agent is recycled on the recovery effect

[0145]

[0146]

[0147] The choline oxalate chloride deep eutectic solvent selected in this embodiment can be recovered by simple evaporation concentration and recycled. The results of ball milling leaching using the deep eutectic solvent showed that the deep eutectic solvent leaching agent maintained a high Li leaching efficiency and selectivity during the 5 cycles. The repeated use of the leaching agent can reduce wastewater discharge and reagent costs, indicating that the method has high economy and sustainability.

[0148] In order to facilitate comparison of the necessity of the method of the present invention, the advantages of the present invention will be described below in conjunction with comparative examples.

[0149] Comparative Example 1

[0150] (1) The waste lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0151] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.55 g of choline chloride and 1.4 g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) were added to a ball mill and milled at 700 rpm for 60 min. After the reaction, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water. After immersion for 3 h, the leachate and precipitate were separated by filtration, and the concentration of metal elements in the leachate was determined by ICP-OES to obtain the leaching rate.

[0152] The other conditions of this comparative example are the same as those of Example 1, except that the ball milling reaction time is 120 min in Example 1 and only 60 min in this comparative example. Fig.12 It can be seen that the leaching rates of lithium, nickel, cobalt, manganese and iron ions in the leachate of this comparative example are 84.05%, 37.85%, 4.49% and 14.57% respectively, and the leaching selectivity is only 59.63%, which is about 36% lower than the leaching selectivity of Example 1. This comparative example shows that a sufficiently long ball milling time can ensure that the mechanochemical reaction is thorough at a certain reaction rate. In the ball milling reaction process of the low eutectic solvent, the ball milling crushing and hydrogen bonding first destroy the crystal structure of the material, release the lithium metal ions therein, and then further reduce the high-valent metal ions, and finally carry out complexation; the ball milling time in this comparative example is short, but the reduction reaction and complexation reaction fail to completely occur. Therefore, the appropriate ball milling time has a strong effect on the stable operation of the system.

[0153] Comparative Example 2

[0154] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0155] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.55 g of choline chloride and 1.4 g of oxalic acid dihydrate (the molar ratio of choline chloride to oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) were added to a ball mill, and the ball milling reaction was carried out at 400 rpm for 120 min. After the reaction, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water. After soaking for 3 h, the leachate and precipitate were separated by filtration, and the metal element concentration in the leachate was determined by ICP-OES to obtain the leaching rate.

[0156] The other conditions of this comparative example are the same as those of Example 1, except that the ball milling speed is 700 rpm in Example 1 and only 400 rpm in this comparative example. Fig.12 It can be seen that the leaching rates of lithium, nickel, cobalt, manganese and iron ions in the leachate of this comparative example are 89.36%, 3.89%, 0.98% and 14.62%, respectively, and the leaching selectivity is only 82.09%, which is about 14% lower than that of Example 1. This comparative example shows that in the ball milling leaching reaction process of the low eutectic solvent, the ball milling reaction first destroys the crystal structure of the positive electrode material, and a sufficient rotation speed provides sufficient strength for the collision and friction between the raw materials in the mechanochemical reaction, which is beneficial to the dissolution of the metal ions and the further reaction with the low eutectic solvent. In this comparative example, the ball milling speed is relatively small. Although it can have a certain destructive effect on the positive electrode material, it fails to completely destroy the crystal structure of the positive electrode material, so that the metal elements in the lattice enter the solution. Therefore, the appropriate ball milling speed has a strong effect on the stable operation of the system.

[0157] Comparative Example 3

[0158] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0159] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, and 1.4 g of oxalic acid dihydrate were added to a ball mill, and the ball milling reaction was carried out at 700 rpm for 120 min. After the reaction was completed, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water. After soaking in water for 3 h, the leachate and precipitate were separated by filtration, and the metal element concentration in the leachate was determined by ICP-OES to obtain the leaching rate.

[0160] The difference between this comparative example and Example 1 is that only organic acid oxalic acid is used as the leaching agent. Fig.12 It can be seen that the leaching rates of nickel, cobalt and manganese ions in the leachate of this comparative example are 6.96%, 3.22% and 15.42% respectively, and the leaching rate of lithium is only 79.80%, and the leaching selectivity for lithium is poor. This shows that although oxalic acid has strong acidity and reducing properties, when it is not mixed with choline chloride in a certain proportion to form a hydrogen bond with strong solubility, only using organic acid oxalic acid for ball milling under certain conditions, the leaching of waste ternary positive electrode materials cannot achieve a good selective leaching effect of lithium.

[0161] Comparative Example 4

[0162] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1cm×1cm. The broken positive electrode sheet is mixed with 2mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying. The calcination is specifically as follows: the black solid powder is calcined at a temperature of 650°C for 3h to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0163] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, and 1.55 g of choline chloride were added to a ball mill, and the ball milling reaction was carried out at 700 rpm for 120 min. After the reaction was completed, the reaction solution in the ball mill was washed into a beaker with 100 ml of deionized water, and the leachate and precipitate were separated by filtration after immersion for 3 h. The concentration of metal elements in the leachate was determined by ICP-OES to obtain the leaching rate.

[0164] The difference between this comparative example and Example 1 is that only the hydrogen bond acceptor choline chloride is used as the leaching agent. Fig.12 It can be seen that the leaching rates of nickel, cobalt and manganese ions in the leaching solution of this comparative example are 0.89%, 0.39% and 0.23% respectively, and the leaching rate of lithium is only 14.36%. This shows that although the low eutectic solvent formed by mixing the hydrogen bond acceptor choline chloride and the hydrogen bond donor oxalic acid has good leaching effect and lithium selectivity, only using the hydrogen bond acceptor choline chloride as a leaching agent and ball milling with the positive electrode material under certain conditions has little leaching effect on the waste ternary positive electrode material.

[0165] Comparative Example 5

[0166] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1cm×1cm. The broken positive electrode sheet is mixed with 2mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3h to remove the binder; finally, the waste ternary lithium battery positive electrode material is obtained.

[0167] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.55 g of choline chloride and 1.2 g of formic acid (the molar ratio of choline chloride to formic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) are added to a ball mill, and the ball milling reaction is carried out at 700 rpm for 120 min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100 ml of deionized water, and the leachate and precipitate are separated by filtration after immersion for 3 h. The concentration of metal elements in the leachate is determined by ICP-OES to obtain the leaching rate.

[0168] The difference between this comparative example and Example 1 is that the oxalic acid in Example 1 is replaced by formic acid. Fig.12 It can be seen that the leaching rates of nickel, cobalt and manganese elements in the leachate of this comparative example are relatively high, reaching 54.67%, 56.97% and 52.64% respectively, which are all higher than the leaching rates of nickel, cobalt and manganese in the waste lithium ion positive electrode material in Example 1. The leaching rate of lithium is only 78.60%, which is lower than the leaching rate in Example 1. This may be due to the weak hydrogen bonding force of the formate-based low eutectic solvent, and the formate group has a poorer complexing ability for nickel, cobalt and manganese ions than the oxalate group, and the corresponding lithium selectivity is also low.

[0169] Comparative Example 6

[0170] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0171] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.55 g of choline chloride and 1.36 g of phosphoric acid (the molar ratio of choline chloride to phosphoric acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) were added to a ball mill and subjected to ball milling reaction at 700 rpm for 120 min. After the reaction, the reaction liquid in the ball mill was washed into a beaker with 100 ml of deionized water. After immersion for 3 h, the leachate and precipitate were separated by filtration. The metal element concentration in the leachate was determined by ICP-OES to obtain the leaching rate.

[0172] The difference between this comparative example and Example 1 is that oxalic acid is replaced by phosphoric acid. Fig.12 It can be seen that the leaching rates of nickel, cobalt and manganese elements in the leachate of this comparative example are relatively high, reaching 54.67%, 56.97% and 52.64% respectively, which are all higher than the leaching rates of nickel, cobalt and manganese in the waste lithium ion positive electrode material in Example 1. The leaching rate of lithium is only 78.60%, which is lower than the leaching rate in Example 1, indicating that the hydrogen bonding force of the phosphate-based low eutectic solvent is weak, and the phosphate group has a poorer complexing ability for nickel, cobalt and manganese ions than the oxalate group, and the corresponding lithium selectivity is also low.

[0173] Table 1 is a comparison of the leaching rates of lithium nickel, cobalt and manganese ions under different reaction conditions in Example 1 and Comparative Examples 1 to 6. It can be seen that in the embodiment of the present invention, oxalic acid-based low eutectic solvents are used for ball milling leaching, and the selectivity of a single hydrogen bond donor or hydrogen bond acceptor and other acid-based low eutectic solvents for lithium ions is not high, indicating the strong effect of hydrogen bonds of oxalic acid-based low eutectic solvents. Similar to oxalate, formate and phosphate also have certain metal complexing abilities. It may be due to the strength of hydrogen bonds, acidity, and complexation with nickel, cobalt, and manganese ions. The acid and phosphate-based low eutectic solvents have poor leaching rates for valuable metal ions and poor selectivity for lithium ions. The experiment found that the leaching rates of lithium ions in these comparative examples were reduced to varying degrees compared with the embodiments, but the leaching rates of nickel, cobalt and manganese ions were improved to varying degrees compared with the embodiments, which are not conducive to the separation of nickel, cobalt and manganese ions from lithium ions, nor to the selective recovery of lithium ions.

[0174] Comparative Example 7

[0175] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0176] (2) Add 90g of ball milling beads and 0.15g of waste ternary cathode material to a ball milling jar, and ball mill at 700rpm for 120min. Add 1.55g of choline chloride and 1.4g of dihydrated oxalic acid to a beaker, and stir and heat at 60°C for 30min until the solid is dissolved to form a uniform transparent solution, which is a low eutectic solvent. Add 0.15g of the cathode material after ball milling to the low eutectic solvent, stir and mix, and react at room temperature for 2h (the molar ratio of choline chloride and oxalic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20). After the reaction is completed, add 100ml of deionized water to the beaker, soak in water for 3h, and then filter to separate the leachate and precipitate. Use ICP-OES to determine the concentration of metal elements in the leachate to obtain the leaching rate.

[0177] The other conditions of this comparative example are the same as those of Example 1, except that the processing steps of this comparative example are to first pre-treat the positive electrode material by ball milling, and then to perform a leaching reaction with the prepared leaching agent low eutectic solvent at room temperature. Fig.13 It can be seen that the leaching rates of lithium, nickel, cobalt and manganese ions in the leachate of this comparative example are 85.65%, 1.35%, 1.51% and 10.15% respectively, and the leaching selectivity is only 86.82%. The leaching selectivity of this comparative example is low and the leaching rate of manganese element is high, which is not conducive to the full recovery of metal elements and the selective separation of lithium ions in the solution. This comparative example shows that in the ball milling leaching reaction process of the low eutectic solvent, the ball milling reaction first destroys the crystal structure of the positive electrode material, and the sufficient rotation speed provides sufficient strength for the collision and friction between the raw materials in the mechanochemical reaction, which is conducive to the dissolution of metal ions and further reaction with the low eutectic solvent. In this comparative example, no co-grinding leaching agent or low eutectic solvent was added during the ball milling process. Although the high-intensity friction, shear force and other forces during the ball milling process can have a certain destructive effect on the positive electrode material, causing the crystal structure of the positive electrode material to collapse, the particle size to decrease, and the specific surface area to increase, the leaching effect may be reduced because there is no mechanochemical action in the subsequent room temperature leaching process to provide sufficient energy to reduce the activation energy of the leaching reaction.

[0178] Comparative Example 8

[0179] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0180] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, 1.30 g of choline chloride and 1.65 g of L-ascorbic acid (the molar ratio of choline chloride to L-ascorbic acid is 1:1, and the mass ratio of cathode material to leaching agent is 1:20) are added to a ball mill and milled at 700 rpm for 120 min. After the reaction is completed, the reaction liquid in the ball mill is washed into a beaker with 100 ml of deionized water. After immersion for 3 h, the leachate and precipitate are separated by suction filtration, and the metal element concentration in the leachate is determined by ICP-OES to obtain the leaching rate.

[0181] The other conditions of this comparative example are the same as those of Example 1, except that the hydrogen bond donor is L-ascorbic acid, which is an organic acid with a strong reducing property and high acidity. Fig.13 It can be seen that the leaching rates of lithium, nickel, cobalt and manganese ions in the leachate of this comparative example are 100%, 100%, 87.74% and 100% respectively, but the leaching selectivity of lithium is only about 25%. Compared with the leaching selectivity of Example 1, which is about 70% lower, this comparative example shows that the low eutectic solvent formed by using strongly reducing and strongly acidic L-ascorbic acid as a hydrogen bond donor and choline chloride has a better leaching reaction effect. After ball milling and room temperature water immersion with the positive electrode material, lithium, nickel and manganese ions are completely leached. However, this type of low eutectic solvent has a very poor leaching selectivity for lithium, and a complex step-by-step separation process is required to recover the valuable metals. The operation is complicated and the amount of reagents consumed is large. A large amount of metal elements will be lost in the complex operation, causing waste. Therefore, the selection of a suitable low eutectic solvent plays an important role in the short-process efficient recovery of valuable metals and the efficient selective separation and recovery of lithium.

[0182] Comparative Example 9

[0183] (1) The waste ternary lithium-ion battery is discharged with a discharger to a voltage of ≤2V, and then manually disassembled to separate the positive electrode sheet, and the positive electrode sheet is cut into pieces of about 1 cm×1 cm. The broken positive electrode sheet is mixed with 2 mol / L NaOH and stirred until no bubbles are generated. The solution is filtered and washed with deionized water for multiple times. The obtained black solid powder is placed in a 60°C oven for drying and then calcined. The specific conditions are: the black solid powder is calcined at 650°C for 3 hours to remove the binder; and finally the waste ternary lithium battery positive electrode material is obtained.

[0184] (2) 90 g of ball milling beads, 0.15 g of waste ternary cathode material, and 10 ml of 2 mol / L sulfuric acid solution were added to a ball mill, and the ball milling reaction was carried out at 700 rpm for 120 min. After the reaction was completed, the reaction solution in the ball mill was washed into a beaker with 100 ml of deionized water. After soaking for 3 h, the leachate and precipitate were separated by filtration, and the metal element concentration in the leachate was determined by ICP-OES to obtain the leaching rate.

[0185] The leaching agent of this comparative example is an inorganic strong acid sulfuric acid solution. Fig.13 It can be seen that after two hours of ball milling reaction, the leaching rate of lithium in the leaching solution of this comparative example is close to 100%, while the leaching rates of nickel and cobalt are relatively low, 60.01% and 47.59% respectively, and manganese is not leached in the material. The high leaching rate of lithium may be due to the fact that lithium is easily deintercalated from the lattice of the positive electrode material after being destroyed by ball milling and sulfuric acid has a strong acidity, and the valence state of nickel, cobalt and manganese in the positive electrode material is relatively high, and it needs to be reduced to low-valent ions for leaching. In current research, hydrogen peroxide is usually added to the sulfuric acid solution as a reducing agent to achieve a high leaching rate of nickel, cobalt and manganese. In addition, inorganic acid sulfuric acid and hydrogen peroxide are highly corrosive, easily causing equipment corrosion, and have poor leaching selectivity and complex separation of valuable metals. This comparative example shows that the selection of a suitable leaching agent plays an important role in the efficient recovery of valuable metals in positive electrode materials and energy saving and environmental protection.

[0186] Table 1 Comparison of leaching rates of lithium, nickel, cobalt and manganese metal ions and lithium leaching selectivity under different reaction conditions in Example 1 and Comparative Examples 1 to 9

[0187]

[0188]

[0189] As can be seen from Table 1, an embodiment of the present invention provides a method for separating and recovering valuable metal elements from waste lithium-ion batteries. The leaching system of the embodiment uses a low eutectic solvent formed by ball milling of oxalic acid and choline chloride as a leaching agent for leaching under ball milling conditions. Under appropriate conditions, the leaching system can not only achieve a high lithium leaching rate of more than 95%, but also show excellent leaching selectivity. This method simultaneously achieves highly selective leaching of lithium ions and separation and recovery of other valuable elements such as nickel, cobalt and manganese. It can be clearly observed from the comparative examples that the type of hydrogen bond donor organic acid constituting the low eutectic solvent has a significant effect on the leaching effect. Comparative Examples 5, 6, 8 and 9, while keeping other conditions consistent with Example 1, replace oxalic acid as a hydrogen bond acceptor with formic acid, phosphoric acid, L-ascorbic acid and sulfuric acid, respectively. The results show that these alternative acids all lead to a decrease in the leaching selectivity of lithium ions. In addition, in Comparative Example 7, while maintaining other conditions unchanged, the ball milling process and the addition of a low eutectic solvent leaching agent are divided into two independent steps. Experimental data show that this operation mode leads to a certain degree of reduction in the leaching rate and selectivity of lithium ions.

[0190] Examples 6, 7 and 8 respectively process waste lithium ion battery positive electrode materials with lithium cobalt oxide, lithium iron phosphate and lithium manganese oxide as positive electrode active materials, and it is found that except for lithium cobalt oxide, the lithium ion leaching selectivity of waste lithium ion batteries with the other two positive electrode materials is reduced to a certain extent when the recycling method of the present invention is used.

[0191] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating and recovering valuable metal elements from waste lithium-ion batteries, characterized in that: The steps include: (1) Separating waste positive electrode materials from waste lithium-ion batteries; (2) mixing the waste positive electrode material obtained in step (1) with a leaching agent and then ball milling to obtain a reaction solution; the leaching agent comprises a hydrogen bond donor and a hydrogen bond acceptor that can be used to form a deep eutectic solvent, wherein the hydrogen bond donor is an organic acid and the hydrogen bond acceptor is a quaternary ammonium salt or an amine compound; (3) The reaction solution of step (2) is transferred out with deionized water, and a water leaching reaction is carried out to convert the nickel, cobalt and manganese metal elements in the reaction solution into a precipitate. After the water leaching reaction is completed, the solid-liquid separation is carried out, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

2. The method according to claim 1, characterized in that The waste positive electrode material is a waste ternary positive electrode material and / or a waste binary positive electrode material, and the waste positive electrode material is one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide and nickel cobalt manganese oxide.

3. The method according to claim 1, characterized in that In step (2), the hydrogen bond donor is one or more of oxalic acid, lactic acid and citric acid; the hydrogen bond acceptor is one or more of choline chloride, betaine hydrochloride and guanidine hydrochloride; The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(0.5-2); the mass ratio of the waste positive electrode material to the leaching agent is 1:(3-30).

4. The method according to claim 1, characterized in that The ball-to-material ratio in the ball milling process of step (2) is (10-100):1, the rotation speed is 100rpm-1000rpm, and the time is 30min-240min.

5. The method according to claim 1, characterized in that In the water leaching reaction described in step (3), the mass ratio of deionized water to the leaching agent is 20-100:1, and the water leaching time is 0.5h-20h.

6. The method according to claim 1, characterized in that The invention also includes the following steps of regenerating and reusing the low eutectic solvent: (4) evaporating the leaching solution containing lithium metal ions to remove water to obtain a regenerated deep eutectic solvent; (5) Separating waste positive electrode materials from waste lithium-ion batteries; (6) using the regenerated low eutectic solvent of step (4) in a new round of waste positive electrode material regeneration process: mixing with the waste positive electrode material obtained in step (5) and then ball milling to obtain a reaction solution; (7) The reaction solution of step (6) is transferred out with deionized water, and subjected to water leaching reaction, so that the nickel, cobalt and manganese metal elements in the reaction solution are fully converted into precipitates. After the water leaching reaction is completed, the solid-liquid separation is performed, and the obtained liquid phase is a leaching solution containing lithium metal ions, and the solid phase is an organic acid complex precipitate containing one or more of nickel, cobalt and manganese.

7. A method for regenerating anode materials of lithium-ion batteries based on the method according to claims 1 to 6, characterized in that: The steps include: S1: Separating a lithium salt from the leaching solution containing lithium metal ions; the lithium salt is lithium carbonate; S2: Determine the content of the metal element in the solid phase, the metal element is the metal element contained in the waste positive electrode material, which is one or more of nickel, cobalt and manganese, and add an appropriate amount of one or more of nickel compounds, cobalt compounds and manganese compounds to the target precursor ratio according to the metal element ratio in the target regenerated positive electrode material; S3: The lithium salt obtained in step S1, the target precursor in step S2, and the lithium source required to be supplemented according to the target regenerated positive electrode material element ratio are mixed evenly, and sintered in an air atmosphere to obtain a regenerated lithium-ion battery positive electrode material.

8. The method according to claim 7, characterized in that In step S2, the nickel compound is at least one of nickel oxalate, nickel acetate, and nickel oxide; the cobalt compound is at least one of cobalt oxalate, cobalt acetate, and cobalt chloride; and the manganese compound is at least one of manganous oxalate, manganese dioxide, and manganous carbonate; When the target regenerated positive electrode material is lithium nickel cobalt manganese oxide, the ratio of the metal elements nickel, cobalt and manganese in the current precursor is 8:1:1, 6:2:2, 5:2:3, 5:3:2 or 1:1:1, and the molar ratio of the valuable metal elements to the lithium element in the target precursor is 1: 1.05 or 1:1.1, and the valuable metal elements include nickel, cobalt and manganese.

9. The method according to claim 7, characterized in that The sintering in step S3 includes the following sub-steps: firstly pre-calcining in an air atmosphere to preliminarily shape the mixture, cooling to room temperature, and obtaining a pre-calcined product; and then performing a secondary calcination on the obtained pre-calcined product in an air atmosphere to obtain a regenerated positive electrode material.

10. The method according to claim 9, characterized in that The pre-calcination temperature is 300-600° C., and the pre-calcination time is 2-8 hours; the secondary calcination temperature is 800-1000° C., and the calcination time is 5-15 hours.

Images