Recycling method of positive electrode material of retired lithium cobalt oxide battery

Abstract

The invention discloses a method for recycling a retired lithium cobalt oxide positive electrode material, which comprises the following steps of: soaking and dissolving a binder in an N-methyl pyrrolidone solvent, stripping a LiCoO2 electrode material from an aluminum foil current collector, soaking the stripped waste LiCoO2 electrode material in an organic acid solution, then transferring the material into a subcritical system, and carrying out vacuum drying to obtain the retired lithium cobalt oxide positive electrode material. And under the assistance of the catalyst, the aim of co-recycling lithium ions and the lithium-removed product cobalt oxalate is fulfilled. According to the method, a SiO2 catalyst is adopted to assist a subcritical system in removing metal lithium and cobalt elements, complete removal of lithium and cobalt can be basically achieved, the removed solution can be converted into lithium carbonate and cobalt oxalate through follow-up treatment and is used for preparing a lithium cobalt oxide electrode material, the electrochemical performance is good, and the operation method is simple in operation process, controllable in condition, high in recovery rate and suitable for industrial production. The method is environment-friendly and beneficial to popularization and utilization.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery resource recycling and reuse, and specifically relates to a method for recycling and reusing retired lithium cobalt oxide battery positive electrode materials. Background Art

[0002] Among lithium-ion batteries, lithium cobalt oxide (LiCoO2) is a common cathode material widely used in consumer electronic devices such as mobile phones, laptops and tablets. Due to the stable performance and high energy density of lithium cobalt oxide batteries, the market demand has always been large. However, with the rapid growth of lithium battery use worldwide, the recycling and disposal of waste batteries has become an important environmental and resource issue. In addition, since cobalt is a rare metal, and the uneven distribution of cobalt resources and the instability of the supply chain, the price of cobalt fluctuates greatly, setting new highs in recent years, especially in the context of the rapid development of the new energy vehicle industry and the surge in demand for lithium batteries. The shortage of cobalt has further pushed up the price. By recycling cobalt from waste batteries, it is possible to reduce dependence on natural cobalt resources and reduce battery manufacturing costs.

[0003] After lithium cobalt oxide batteries are discarded, if they are not properly treated, heavy metals such as cobalt, lithium, nickel, and organic electrolytes in the batteries may leak, pollute the soil and water, and harm the environment and ecosystem. Recycling lithium cobalt oxide can avoid high energy consumption and environmental pollution in the process of mining the original ore. According to research, the energy consumption of recycling cobalt is much lower than that of mining new cobalt, and it can also reduce carbon emissions, which is in line with the global carbon neutrality goal. The complexity and technical challenges of recycling lithium cobalt oxide batteries mainly include: The recovery rate of cobalt and lithium in lithium cobalt oxide batteries is an important indicator for evaluating the recycling process. How to optimize the process and improve economic benefits is the key development direction of lithium cobalt oxide recycling technology. At present, there are two main methods for recycling lithium cobalt oxide batteries: pyrometallurgy and hydrometallurgy. Among them, pyrometallurgy has high energy consumption and may cause secondary pollution; while the hydrometallurgical process is relatively complex, and the problem of waste liquid treatment needs to be properly solved. At present, there is no report on the recovery of lithium cobalt oxide positive electrode materials by constructing a subcritical system to assist catalysis. Summary of the invention

[0004] The present invention aims to avoid the shortcomings of the above-mentioned prior art and to provide a method for recycling and reusing retired lithium cobalt oxide battery positive electrode materials under the condition of fully considering economic benefits, by constructing a subcritical system to assist catalysis in recycling and reusing the lithium cobalt oxide battery positive electrode materials. The method of the present invention can achieve the recovery of both metallic lithium and metallic cobalt, and further be used to prepare lithium cobalt oxide electrode materials. The method of the present invention has a simple operation process, controllable conditions, high recovery rate, and is environmentally friendly, which is conducive to promotion and application.

[0005] The technical solution of the present invention is as follows: A method for recycling and reusing retired lithium cobalt oxide battery positive electrode materials, specifically comprising the following steps: Step 1: Leaching lithium and cobalt ions from retired lithium cobalt oxide electrode positive electrode materials: In order to prevent spontaneous combustion and short circuit during the disassembly process, the battery must be discharged first. The battery was immersed in a 10% NaCl solution (w / v) for 12 hours to complete the discharge, then rinsed four times with ultrapure water and dried in an oven at 60°C for 12 hours. The aluminum film was manually disassembled, and the anode, cathode and diaphragm were separated. The binder in the waste lithium cobalt oxide electrode material was dissolved by soaking in N-methylpyrrolidone solvent, and then LiCoO2 was peeled off from the aluminum film. The obtained material was fully ground with a mortar and prepared for the leaching experiment; the obtained waste lithium cobalt oxide material was immersed in an organic acid solvent and stirred for 1 hour, and then transferred to a high-temperature and high-pressure reactor for leaching, and SiO2 dielectric material was added as a catalyst to obtain a leaching solution; the subcritical state was constructed by controlling the reaction temperature, reaction pressure and leaching time, and lithium ions and cobalt ions were selectively leached from the lithium cobalt oxide positive electrode active material, and the SiO2 catalyst material was recovered.

[0006] Step 2: adding a precipitant sodium oxalate to the leaching solution obtained in step 1, and obtaining cobalt oxalate by centrifugal washing and drying; after removing cobalt ions from the solution by precipitation, adding a precipitant sodium carbonate to produce lithium carbonate precipitation, and the obtained cobalt oxalate and lithium carbonate are used as raw materials to prepare lithium cobalt oxide electrode materials, which can then be recycled and reused.

[0007] Step 3: The cobalt oxalate and lithium carbonate recovered in step 2 are mixed according to a ratio and dispersed in ethanol, ball-milled and dried, and ground to obtain a precursor, which is placed in a calcination boat and calcined in a tube furnace in a protective atmosphere, first heated to 300-500° C. for 1-6 hours, then heated to 600-900° C. for 1-20 hours, and cooled to room temperature to obtain a lithium cobalt oxide electrode material.

[0008] Preferably, in step 1, the organic acid solvent is at least one of citric acid, succinic acid and malic acid; and the concentration of the organic acid is 0.1-0.5 mol / L.

[0009] Preferably, in step 1, the amount of the waste lithium cobalt oxide positive electrode material is 300 mg to 800 mg; and the amount of SiO2 catalyst added is 40 to 120 mg.

[0010] Preferably, in step 1, the reaction temperature is 120° C. to 180° C.; the reaction pressure is 1 MPa to 5 MPa; and the leaching time is 6 h to 12 h.

[0011] Preferably, in step 2, the sodium oxalate precipitant and the lithium carbonate precipitant are both saturated solutions.

[0012] Preferably, in step 3, when the cobalt oxalate and the lithium carbonate are mixed, the molar ratio of Li:Co is controlled to be (0.9-1.5):1.

[0013] Preferably, in step 3, the ball milling time is 0.5-15 h, and the ball milling speed is 10-1000 rpm / min.

[0014] Preferably, in step 3, the protective atmosphere is one or more of nitrogen, argon, carbon monoxide, argon hydrogen, and hydrogen.

[0015] Preferably, in step 3, the heating rate of the tube furnace is 1-8°C / min.

[0016] The present invention has the following beneficial effects: At present, there are two main methods for recycling lithium cobalt oxide batteries: pyrometallurgy and hydrometallurgy. Among them, pyrometallurgy has high energy consumption and may cause secondary pollution; while hydrometallurgy is relatively complex, and the problem of waste liquid treatment needs to be properly solved. The present invention adopts the construction of a subcritical system to assist in catalytic recovery of metallic lithium and cobalt, with a high leaching rate, and the leached solution is subsequently treated and converted for the cyclic preparation of lithium cobalt oxide electrode materials, and the electrochemical performance is good. Compared with the existing pyrometallurgy and hydrometallurgy, the present invention has less pollution and good recycling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) is an X-ray diffraction (XRD) diagram of LiCoO2 before recovery and SiO2 after recovery according to the present invention, and (b) is a Fourier transform infrared spectrum (FTIR) diagram of LiCoO2 before recovery and SiO2 after recovery; Figure 2 (a) is an X-ray diffraction (XRD) diagram of cobalt oxalate and lithium carbonate after recovery according to the present invention, and (b) is a Fourier transform infrared spectrum (FTIR) diagram of cobalt oxalate and lithium carbonate after recovery; Figure 3 (a) is a field emission scanning electron microscope (FESEM) image of LiCoO2 before recycling of the present invention, (b) is a SEM image of SiO2 after recycling, (c) is a SEM image of cobalt oxalate after recycling, and (d) is a SEM image of lithium carbonate; Figure 4 The charge-discharge curve diagram of lithium cobalt oxide prepared by using the cobalt oxalate and lithium carbonate recovered by the present invention as raw materials; Figure 5 The cycle performance diagram at 0.5C is a graph of lithium cobalt oxide prepared by using the cobalt oxalate and lithium carbonate recovered by the present invention as raw materials; Figure 6 The electrochemical impedance spectrum (EIS) diagram of lithium cobalt oxide prepared by using the cobalt oxalate and lithium carbonate recovered by the present invention as raw materials. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further analyzed and explained below through specific embodiments.

[0019] The present invention provides a method for recycling and reusing retired lithium cobalt oxide battery positive electrode materials, comprising the following steps: Step 1: Leaching lithium and cobalt ions from retired lithium cobalt oxide cathode materials: To prevent spontaneous combustion and short circuit during disassembly, the battery must be discharged first. The battery was immersed in a 10% NaCl solution (w / v) for 12 h to complete the discharge, then rinsed four times with ultrapure water and dried in an oven at 60 ° C for 12 h. The aluminum film was manually disassembled, and the anode, cathode and diaphragm were separated. The binder in the waste lithium cobalt oxide electrode material was dissolved by soaking in N-methylpyrrolidone solvent, and then LiCoO2 was peeled off from the aluminum film. The obtained material was fully ground in a mortar and prepared for the leaching experiment; 400 mg of waste lithium cobalt oxide material was weighed and soaked in 40 mL of 0.2 mol / L citric acid solution, stirred for 1 hour, and then transferred to a high-temperature and high-pressure reactor, and 80 mg of SiO2 dielectric material was added as a catalyst. The reaction temperature was adjusted to 150 ° C and the reaction pressure was 3 MPa. After leaching for 9 hours, the leached solution was tested by inductively coupled plasma spectrometer (ICP-MS) to obtain the concentration of lithium ions and cobalt ions in the leached solution. The lithium removal rate and cobalt removal rate were calculated to be more than 98%, as shown in Table 1. The catalyst material SiO2 after leaching was recovered and compared with the XRD before leaching. Figure 1 (a) shows the FTIR analysis of Figure 1 As shown in (b), the SiO2 catalyst material crystal form is transformed into an amorphous state, and the composition does not change. Figure 3 As shown in (a) and (b).

[0020] Step 2: Recycling of retired lithium cobalt oxide cathode materials: Add 500 mg of sodium oxalate to the leaching solution obtained in step 1, stir at room temperature for 30 minutes, and then centrifuge to obtain sodium oxalate precipitate and lithium solution. The lithium ion solution obtained in the previous step is reacted with saturated sodium carbonate, stirred at 95°C for 2 hours, and then a white lithium carbonate precipitate is extracted from the solution by centrifugation. The obtained cobalt oxalate and lithium carbonate are used as raw materials to prepare lithium cobalt oxide electrode materials, which can be recycled and reused. Figure 2 The XRD and FTIR diagrams of the cobalt oxalate and lithium carbonate recovered from the treatment are shown in Figure 1. The cobalt oxalate has a complete crystal form, no impurity peaks, and a high purity. The crystallinity of lithium carbonate is poor, but the composition is basically correct. Figure 3 As shown in (c) and (d).

[0021] Step 3: Recycling of retired lithium cobalt oxide cathode materials The cobalt oxalate and lithium carbonate recovered in step 2 are mixed according to the proportion and dispersed in ethanol, and the molar ratio of Li:Co is controlled to be 1.05:1. The ball mill is milled at a speed of 400 rpm / min for 10 hours. After the ball milling, it is dried at 80°C for 6 hours and ground for 0.5 hours to obtain a precursor. The precursor is placed in a calcination boat and calcined in a tubular furnace in a nitrogen atmosphere. First, the temperature is increased to 350°C at 4°C / min and calcined for 4 hours, and then the temperature is increased to 750°C at 2°C / min and calcined for 10 hours. Cool to room temperature to obtain a lithium cobalt oxide electrode material.

[0022] Step 4: Preparation of positive electrode Weigh 0.3 g of lithium cobalt oxide positive electrode active material, 0.0375 g of conductive agent acetylene black and 0.0375 g of binder polyvinylidene fluoride (PVDF) and mix them. Use 1-methyl-2-pyrrolidone (NMP) to prepare the mixture into slurry, evenly apply it on the current collector aluminum foil, dry it, and slice it to make a positive electrode sheet.

[0023] Electrochemical test: The experimental battery was assembled in an argon glove box with a metal lithium sheet as the negative electrode, Cellgard 2400 polypropylene membrane as the separator, and 1 mol / L LiPF6 solution (ethylene carbonate + dimethyl carbonate (volume ratio = 1:1)) as the electrolyte. Then, the battery was subjected to a constant current charge and discharge experiment at 25°C. The results are shown in the figure. Figure 4 shown.

[0024] Electrochemical tests showed that the capacities were 188 mAh / g and 162.1 mAh / g at 0.2C and 1C, respectively.

[0025] like Figure 5 As shown in the figure, from its cycle performance diagram at 0.5C, it can be seen that its capacity retention rate can reach 94% after 120 cycles.

[0026] from Figure 6 It can be seen that lithium cobalt oxide batteries have smaller charge transfer resistance and diffusion resistance.

[0027] Table 1 is a table of inductively coupled plasma spectrometer (ICP-MS) test results after the solution was leached in the embodiment.

[0028] Table 1 Electrode Materials Catalyst SiO2 dosage / mg Active substance mass / mg Lithium ion concentration in leachate (g / L) Lithium removal rate (%) Cobalt ion concentration in leachate (g / L) Cobalt removal rate (%) Lithium cobalt oxide 80 400 0.701 98.1 5.926 98.3 The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries, characterized in that: The steps include: Step 1: soaking and dissolving the retired lithium cobalt oxide battery in an N-methylpyrrolidone solvent to obtain a peeled retired lithium cobalt oxide battery positive electrode material, immersing the retired lithium cobalt oxide battery positive electrode material in an organic acid solvent and stirring for 1 hour, and then transferring it to a high-temperature and high-pressure reactor for leaching, adding a SiO2 dielectric material as a catalyst, and obtaining a leaching solution; Step 2: adding a precipitant sodium oxalate to the leaching solution, washing and drying by centrifugation to obtain cobalt oxalate, removing cobalt ions from the solution by precipitation, and then adding a precipitant sodium carbonate to produce lithium carbonate precipitation to obtain lithium carbonate; Step 3: Mix the cobalt oxalate and the lithium carbonate in a proportion and disperse them in ethanol, ball mill and dry, grind to obtain a precursor, place the precursor in a calcination boat, and calcine in a tube furnace in a protective atmosphere, first heat to 300-500°C for 1-6h, then heat to 600-900°C for 1-20h, and cool to room temperature to obtain a lithium cobalt oxide positive electrode material.

2. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 1, the organic acid solvent is at least one of citric acid, succinic acid and malic acid; and the concentration of the organic acid is 0.1-0.5 mol / L.

3. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 1, the amount of the retired lithium cobalt oxide battery positive electrode material is 300 mg to 800 mg; the amount of the SiO2 catalyst added is 40 to 120 mg.

4. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 1, the reaction temperature is 120° C. to 180° C., the reaction pressure is 1 MPa to 5 MPa, and the leaching time is 6 h to 12 h.

5. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 2, when the cobalt oxalate and the lithium carbonate are mixed, the molar ratio of Li:Co is controlled to be (0.9-1.5):

1.

6. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 3, the ball milling time is 0.5-15 h, and the ball milling speed is 10-1000 rpm / min.

7. The method for recycling and reusing the positive electrode material of retired lithium cobalt oxide batteries according to claim 1, characterized in that: In step 3, the protective atmosphere is one or more of nitrogen, argon, carbon monoxide, argon hydrogen, and hydrogen.

8. The method for recycling and reusing retired lithium cobalt oxide battery positive electrode materials according to claim 1, characterized in that: In step 3, the heating rate of the tubular furnace is 1-8°C / min.

Images