Method for preparing electrocatalyst by efficiently recovering nickel, cobalt and manganese from waste lithium battery

Abstract

The application discloses a method for preparing an electrocatalyst by efficiently recycling nickel, cobalt and manganese from waste lithium batteries. The method comprises the following steps: subjecting a positive pole piece of a disassembled waste lithium battery to heat treatment to separate a powdery positive pole material and an aluminum foil; and adding the powdery positive pole material and the aluminum foil into a deep eutectic solvent to leach nickel, cobalt, manganese and lithium ions through a deep eutectic solvent of a choline chloride-organic acid-alcohol-water system, adjusting the ratio of alcohol to water to achieve the function of a surfactant, and adding a precipitant to prepare the electrocatalyst containing nickel, cobalt and manganese and having a uniform morphology through a hydrothermal method. The deep eutectic solvent used in the application is safe, non-toxic, low in eutectic temperature and capable of being prepared at room temperature, and has the advantages of recyclability. The prepared electrocatalyst is uniform, high in catalytic efficiency and good in application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of recycling and reusing waste lithium batteries, and particularly relates to a method for efficiently recovering nickel, cobalt and manganese from waste lithium batteries to prepare an electrocatalyst. BACKGROUND

[0002] With the popularization and use of electric vehicles in China, the amount of scrapped ternary lithium batteries increases year by year, and the problems of recycling and processing of waste lithium batteries are becoming increasingly serious. Since ternary lithium batteries contain metal elements such as lithium, nickel, cobalt, aluminum and manganese, they are an important "urban mine". Random disposal not only causes waste of non-renewable and valuable metal resources, but also causes pollution to the atmosphere, water bodies and soil. Therefore, realizing the standardized recycling and efficient utilization of lithium batteries is an important part of promoting the sustainable development of China, and is also an inevitable demand for building a resource-conserving and environment-friendly society.

[0003] At present, the main ways of recycling waste lithium are fire method, wet method, biological method and mechanical method. The metal leaching rate of wet metallurgy is high, and the purity of the recovered product is high. However, wet metallurgy usually needs to use inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid, which poses a threat to the health of operators and the environment (Zeng, X., Li, J. & Singh, N. Recycling of spent lithium-ion battery: a critical review. Crit. Rev. Env. Sci. Tech. 44, 1129-1165 (2014)).

[0004] Deep eutectic solvents are considered as a new type of green solvent related to ionic liquids, which are composed of hydrogen bond donors and acceptors. Deep eutectic solvents have low melting point, strong solvation ability and expandable hydrogen network, allowing metal ions to coordinate, so they have great application potential in recycling valuable metal elements from waste lithium batteries. However, due to the molecular radius of deep eutectic solvents being larger than the voids in the solution, they exhibit high viscosity and eutectic point, which is not conducive to the leaching and separation of valuable metals at low temperatures. SUMMARY

[0005] The purpose of the present application is to recycle and utilize waste lithium batteries, and to provide a method for efficiently recovering nickel, cobalt and manganese to prepare an electrocatalyst. The method uses a deep eutectic solvent of choline chloride-organic acid-alcohol-water system to leach nickel, cobalt, manganese and lithium ions, adjusts the ratio of alcohol to water to achieve the effect of a surfactant, and hydrothermally prepares an electrocatalyst containing nickel, cobalt and manganese with uniform morphology by adding a precipitating agent. The deep eutectic solvent used in the present application is safe, non-toxic, has a low eutectic temperature and can be prepared at room temperature, and has the advantages of recyclability. The prepared electrocatalyst is uniform, has high catalytic efficiency, and has good application prospects.

[0006] The technical scheme of the present application is:

[0007] A method for preparing an electrocatalyst by efficiently recovering nickel, cobalt and manganese from waste lithium batteries, comprising the following steps:

[0008] (1) heat treating the positive electrode sheet of the disassembled waste lithium battery to separate and obtain a powdery positive electrode material and an aluminum foil;

[0009] (2) adding the powdery positive electrode material obtained in step (1) to a deep eutectic solvent, stirring at 10-100℃ for 0.1-10h to obtain a leaching solution containing nickel, cobalt, manganese and lithium ions;

[0010] The deep eutectic solvent comprises choline chloride, an organic acid, an alcohol and water, the molar ratio of choline chloride to the organic acid is 2:1-1:5, the volume ratio of water to the alcohol is 2:1-1:5, the mass ratio of water in the deep eutectic solvent is 5%-40%, and the solid solution ratio of the powdery positive electrode material to the deep eutectic solvent is 1:30-1:100;

[0011] The organic acid is one or more of citric acid, ascorbic acid and lactic acid, and the alcohol is one or more of methanol, ethanol, isopropanol and ethylene glycol.

[0012] (3) preparing a precipitant solution and adding it to the leaching solution, sealing in an autoclave and reacting at 100-220℃ for 0.1-20h to selectively precipitate nickel, cobalt and manganese ions, and then filtering and washing to obtain an electrocatalyst containing nickel, cobalt and manganese;

[0013] The mass ratio of the precipitant to the solvent is 1:20-1:5, and the volume ratio of the precipitant solution to the leaching solution is 1:1-1:10;

[0014] The precipitant is one of oxalic acid, boric acid, thiourea and sodium carbonate, the solvent is a mixed solution of water and an alcohol, the alcohol is one or more of methanol, ethanol, isopropanol and ethylene glycol, and the volume ratio of water to the alcohol is 2:1-1:5.

[0015] The waste lithium battery is one or more of NCM111, NCM523, NCM622 and NCM811 type ternary lithium batteries.

[0016] In the preparation method, the temperature for heat treating the positive electrode sheet in step (1) is 200-600℃, and the heat treatment time is 1-10h.

[0017] In the preparation method, the stirring temperature in step (2) is 10-100℃, and the stirring time is 0.1-10h.

[0018] The application of the electrocatalyst obtained by the method is used for the oxygen evolution catalytic reduction of oxygen atoms into oxygen in a fuel cell.

[0019] The substantial features of the present application are:

[0020] The present application adopts the deep eutectic solvent of choline chloride-organic acid-alcohol-water system to efficiently recover nickel, cobalt and manganese in waste lithium batteries. The deep eutectic solvent of choline chloride-organic acid-alcohol-water system extracts lithium ion at low temperature (the hydrogen bond donor organic acid can effectively leach the metal, and the choline chloride can provide chloride ions to speed up the dissolution of the metal, the addition of ethylene glycol and water can reduce the viscosity to improve the leaching efficiency, and the ethylene glycol can act as a reducing agent to participate in the reaction.), and under hydrothermal conditions, it acts as a mother liquor to participate in the formation of the catalyst with a template agent (the polarity and viscosity of the solvent itself affect the growth speed of the anisotropy of oxalate, and due to the complexation of metal ions with ethylene glycol and citrate, the reaction of metal ions with oxalate is slow, and the oxalate with a microrod structure is generated); the ratio of alcohol to water not only reduces the eutectic point, but also participates in the reaction as a template agent.

[0021] The recovered material obtained by the present application has the characteristics of low cost, high reaction activity and stable structure, and can be used as a high-performance electrocatalyst. The method is simple, easy to control, the deep eutectic solvent can be recycled, and the synthesized electrocatalyst is uniform and has high catalytic efficiency.

[0022] The present application has the following advantages:

[0023] 1. The present application provides a new idea for recycling waste lithium batteries, i.e. using ternary positive materials in waste lithium batteries to prepare high-performance electrocatalysts, achieving the purpose of waste treatment.

[0024] 2. The present application proposes a deep eutectic solvent of choline chloride-organic acid-alcohol-water system, which can greatly reduce the eutectic temperature compared to the choline chloride-organic acid system (from 69 DEG C to room temperature, which means that more cost can be saved and the deep eutectic solution can be prevented from recrystallizing during the extraction process), and the deep eutectic solvent can be prepared at room temperature, which is green and efficient.

[0025] 3. The present application can leach nickel, cobalt and manganese lithium ions in the choline chloride-organic acid-alcohol-water system at a relatively low temperature, and then selectively synthesize electrocatalysts containing nickel, cobalt and manganese using a precipitating agent, which has a simple preparation process and excellent catalytic performance. Compared with industrial IrO2 (overpotential 290mv, 10mA cm -2 , the potential can work stably), it has a low potential of 273mV at a current density of 10mA cm -2 , and can work stably at a potential of 10mA cm -2 for 20 hours. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 XRD picture of nickel cobalt manganese oxalate oxygen evolution catalyst of Example 1;

[0027] Figure 2 SEM picture of nickel cobalt manganese oxalate oxygen evolution catalyst of Example 1;

[0028] Figure 3 Oxygen evolution performance of nickel cobalt manganese oxalate oxygen evolution catalyst of Example 1;

[0029] Figure 4 Stability performance of nickel cobalt manganese oxalate oxygen evolution catalyst of Example 1;

[0030] Figure 5 SEM picture of nickel cobalt manganese sulfide oxygen evolution catalyst of Example 2; DETAILED DESCRIPTION

[0031] The following examples are intended to further illustrate the present application and are not intended to limit the same.

[0032] Example 1:

[0033] The first step is to heat-treat the positive electrode sheet of the disassembled waste lithium battery to separate the powdery positive electrode material and the aluminum foil, and the specific steps are as follows:

[0034] The positive electrode sheet of the waste ternary lithium battery (NCM111 type, the positive electrode material is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) is used as raw material, which is placed in a muffle furnace to remove the binder at 450℃ for 3h, and finally the powdery positive electrode material is peeled off from the aluminum foil.

[0035] The second step is the preparation of deep eutectic solvent of choline chloride-organic acid-alcohol-water system and ion leaching, and the specific steps are as follows:

[0036] 13.9g of choline chloride (i.e. 0.1mol) and 21.4g of citric acid (i.e. 0.1mol) are dissolved in a solution of 90mL of ethylene glycol and 30mL of water to obtain a deep eutectic solvent, and 2g of powdery positive electrode material is added to the above deep eutectic solvent, which is stirred at 90℃ for 2h to obtain a leaching solution.

[0037] The third step is the preparation of precipitant solution and selective precipitation of metal ions, and the specific steps are as follows:

[0038] 8.4 g of oxalic acid was dispersed in a mixed solution of 60 mL ethylene glycol and 20 mL water to obtain a precipitant solution. The precipitant solution was added to the above leachate at room temperature to obtain a suspension. The suspension was then subjected to hydrothermal treatment in a high-temperature pressure vessel at 180 °C for 12 h. After filtration and washing, a nickel-cobalt-manganese electrocatalyst (specifically NCM oxalate, with the chemical formula approximately Ni) was obtained. 0.33 Co 0.33 Mn 0.33 The yield of C2O4 is approximately 2.1g.

[0039] The filtrate contains a deep eutectic solution and lithium oxalate, which can be used for subsequent regeneration of the deep eutectic solution and enrichment of lithium.

[0040] The sample was analyzed using a Rigaku Smartlab 9KW X-ray diffractometer (Japan), and the results are as follows: Figure 1 The image shows cobalt oxalate with single-phase properties. Compared to pure-phase cobalt oxalate (JCPDS No. 037-0719), the diffraction peak of NCM oxalate is significantly shifted to the left, which is due to lattice expansion caused by Ni ions substituting for Co ions. Using a JEOL 7610F scanning electron microscope, the morphology of the sample was observed to be uniformly sized as oxalate microrods with a length of 20-30 μm and a width of 4-5 μm. Figure 2 The prepared nickel-manganese-cobalt catalyst was mixed evenly with 80 wt.% of the raw materials, 10 wt.% of acetylene black, and 10 wt.% of PVDF to form a slurry. This slurry was then uniformly coated onto a carbon cloth with one side treated with a hydrophilic coating. The amount of active material (i.e., the mass of oxalate) per unit area was 2-3 mg / cm². 2 After vacuum drying, the electrode was assembled into a working electrode and its electrochemical performance was tested in a 1 mol / L KOH solution with a graphite rod as the counter electrode, a mercuric oxide electrode as the reference electrode, and a graphite rod as the electrolyte. The step-cycle voltammetry method was used with a voltage range of 1.1–1.9 V (VS.RHE), a transition potential of 0.05 V, and a holding time of 200 s per step. The oxygen production performance results are as follows: Figure 3 As shown, the material at 10 mA cm -2 It exhibits a low potential of 273mV (100% IR compensation) at a current density of 10mA cm⁻¹. -2 The potential was tested using the potentiostatic method, and the stability results are as follows: Figure 4 As shown, the material rises and falls over 20 hours until it decays by 10%.

[0041] Example 2:

[0042] The first step is to heat-treat the positive electrode sheets from the dismantled waste lithium batteries to separate the powdered positive electrode material and aluminum foil. The specific steps are as follows:

[0043] The positive electrode sheet (NCM523 type, positive electrode material LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) of the waste ternary lithium battery was used as raw material, and was placed in a muffle furnace at 500 DEG C for 2h to remove the binder, and finally the powdery positive electrode material was peeled off from the aluminum foil.

[0044] The second step was the preparation of deep eutectic solvent of choline chloride-organic acid-alcohol-water system and ion leaching, and the specific steps were as follows:

[0045] 13.9g (0.1mol) choline chloride and 19.6g (0.1mol) ascorbic acid were dissolved in a solution of 90mL ethylene glycol and 30mL water to obtain a deep eutectic solvent, and 2g of powdery positive electrode material was added to the deep eutectic solvent, and was stirred at 90 DEG C for 2h to obtain a leaching solution.

[0046] The third step was the preparation of precipitant solution and selective precipitation of metal ions, and the specific steps were as follows:

[0047] 7.6g (0.1mol) thiourea was dispersed in a mixed solution of 60mL ethylene glycol and 20mL water to obtain a precipitant solution. The precipitant solution was added to the leaching solution at room temperature to obtain a suspension, which was hydrothermally treated in a high-temperature pressure kettle at 160 DEG C for 10h, and then was filtered and washed to obtain a nickel-cobalt-manganese sulfide electrocatalyst.

[0048] The sample morphology was observed by using a Japanese JEOL7610F type scanning electron microscope, and it was found that the nickel-manganese-cobalt sulfide catalyst had uniform size Figure 5 ). As shown in the figure, it was a spherical structure with a diameter of about 10 microns.

[0049] Example 3:

[0050] The first step was to heat-treat the positive electrode sheet of the disassembled waste lithium battery to separate the powdery positive electrode material and the aluminum foil, and the specific steps were as follows:

[0051] The positive electrode sheet (NCM111 type, positive electrode material LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) of the waste ternary lithium battery was used as raw material, and was placed in a muffle furnace at 500 DEG C for 2h to remove the binder, and finally the powdery positive electrode material was peeled off from the aluminum foil.

[0052] The second step was the preparation of deep eutectic solvent of choline chloride-organic acid-alcohol-water system and ion leaching, and the specific steps were as follows:

[0053] A deep eutectic solvent was prepared by dissolving 13.9 g (0.1 mol) of choline chloride, 10.7 g (0.05 mol) of citric acid and 9.8 g (0.05 mol) of ascorbic acid in a solution of 90 mL of isopropyl alcohol and 30 mL of water. 2 g of the powdery positive electrode material was added to the deep eutectic solvent, and stirring was performed at 80°C for 2 h to obtain a leaching solution.

[0054] The third step was preparation of a precipitant solution and selective precipitation of metal ions, and the specific steps were as follows:

[0055] A precipitant solution was prepared by dispersing 6.0 g (0.1 mol) of urea in a mixed solution of 60 mL of isopropyl alcohol and 20 mL of water. The precipitant solution was added to the leaching solution at room temperature, and hydrothermal treatment was performed in a high-temperature pressure kettle at 180°C for 12 h. Filtration and washing were performed to obtain an electric catalyst containing nickel, cobalt and manganese.

[0056] Example 4:

[0057] The first step was heat treatment of the positive electrode sheet of the disassembled waste lithium battery, and the powdery positive electrode material and aluminum foil were separated, and the specific steps were as follows:

[0058] The positive electrode sheet (NCM811 type, and the positive electrode material was LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) of the waste ternary lithium battery was used as a raw material, and was placed in a muffle furnace, and the binder was removed at 450°C for 2 h. Finally, the powdery positive electrode material was peeled off from the aluminum foil.

[0059] The second step was preparation of a deep eutectic solvent of a choline chloride-organic acid-alcohol-water system and ion leaching, and the specific steps were as follows:

[0060] A deep eutectic solvent was prepared by dissolving 13.9 g (0.1 mol) of choline chloride and 21.4 g of citric acid (0.1 mol) in a solution of 90 mL of ethylene glycol and 30 mL of water. 2 g of the powdery positive electrode material was added to the deep eutectic solvent, and stirring was performed at 90°C for 2 h to obtain a leaching solution.

[0061] The third step was preparation of a precipitant solution and selective precipitation of metal ions, and the specific steps were as follows:

[0062] A precipitant solution was prepared by dispersing 6.18 g (0.1 mol) of boric acid in a mixed solution of 60 mL of ethylene glycol and 20 mL of water. The precipitant solution was added to the leaching solution at room temperature to obtain a suspension, and hydrothermal treatment was performed in a high-temperature pressure kettle at 160°C for 12 h. Filtration and washing were performed to obtain an electric catalyst containing nickel, cobalt and manganese.

[0063] In summary, the present application leaches nickel, cobalt, manganese and lithium ions by a deep eutectic solvent of choline chloride-organic acid-alcohol-water system, and obtains an electrocatalyst containing nickel, cobalt and manganese by hydrothermal preparation through adding a precipitant. The deep eutectic solvent used in the present application is safe and non-toxic, has a low eutectic temperature and can be prepared at normal temperature, and has the advantages of recyclability, and the prepared electrocatalyst is uniform and has high catalytic efficiency.

[0064] The details of the present application are known in the art.

Claims

1. A method for efficiently recovering nickel, cobalt, and manganese from spent lithium batteries to prepare electrocatalysts, characterized in that the method includes the following steps: (1) Heat treatment is performed on the positive electrode sheet of the disassembled waste lithium battery to separate the powdered positive electrode material and aluminum foil. The waste lithium batteries are one or more of the following: NCM111, NCM523, NCM622, and NCM811 ternary lithium batteries. (2) Add the powdered positive electrode material obtained in step (1) into a deep eutectic solvent and stir at 10 to 100°C for 0.1 to 10 hours to obtain a leachate containing nickel, cobalt, manganese and lithium ions. The deep eutectic solvent includes choline chloride, organic acid, alcohol and water, wherein the molar ratio of choline chloride to organic acid is 2:1 to 1:5; the volume ratio of water to alcohol is 2:1 to 1:5; the mass ratio of water to deep eutectic solvent is 5% to 40%; and the solid-solution ratio of powdered cathode material to deep eutectic solvent is 1:30 to 1:

100. The organic acid is one or more of citric acid, ascorbic acid, and lactic acid; the alcohol is one or more of methanol, ethanol, isopropanol, and ethylene glycol. (3) Add the precipitant solution to the above leachate, seal it in a high-pressure reactor, and react at 100-220°C for 0.1-20 h; so that nickel, cobalt and manganese ions are selectively precipitated, and the electrocatalyst containing nickel, cobalt and manganese is obtained by filtration and washing. The mass ratio of precipitant to solvent is 1:20 to 1:5; the volume ratio of precipitant solution to leachate is 1:1 to 1:

10.

2. The method for efficiently recovering nickel, cobalt, and manganese from spent lithium batteries to prepare electrocatalysts as described in claim 1, characterized in that: The precipitant is one of oxalic acid, boric acid, thiourea, and sodium carbonate; the solvent is a mixed solution of water and alcohol, and the alcohol is one or more of methanol, ethanol, isopropanol, and ethylene glycol; the volume ratio of water to alcohol is 2:1 to 1:

5.

3. The method for efficiently recovering nickel, cobalt, and manganese from spent lithium batteries to prepare electrocatalysts as described in claim 1, characterized in that: In the preparation method described above, the temperature for heat treatment of the positive electrode sheet in step (1) is 200-600℃, and the heat treatment time is 1-10h.

4. The method for efficiently recovering nickel, cobalt, and manganese from spent lithium batteries to prepare electrocatalysts as described in claim 1, characterized in that: In the preparation method described above, the leaching and stirring temperature in step (2) is 10-100℃, and the stirring time is 0.1-10h.

5. The application of the electrocatalyst obtained by the method of claim 1, characterized in that the oxygen evolution catalytic reduction of oxygen atoms in fuel cells is oxygen gas.

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