Method for recycling positive electrode material of waste lithium cobalt oxide battery

Abstract

The invention discloses a method for recycling a positive electrode material of a waste lithium cobalt oxide battery. The recycling method comprises the following steps: uniformly mixing positive electrode powder disassembled from the waste lithium cobalt oxide battery with oxalic acid containing crystal water, reacting at 120-180 DEG C for 1-5 hours, then adding water into a reaction product, cleaning, filtering and drying to obtain cobalt oxalate precipitate; the preparation method comprises the following steps: ball-milling cobalt oxalate and 2-methylimidazole, uniformly mixing, and reacting at 60-150 DEG C for 12-48 hours to obtain the metal-organic framework material ZIF-67. According to the method disclosed by the invention, the ZIF-67 is prepared by taking the positive electrode material of the waste lithium cobalt oxide battery as the cobalt source, and the method has the characteristics of simple process, low cost, no generation of organic waste liquid and no pollution to the environment; according to the method, the recycled waste lithium cobalt oxide batteries are used for preparing the functional material, waste reutilization and environmental protection are achieved, important economic value and social benefit are achieved, and more thoughts and schemes are provided for improving the additional value application of the waste batteries.

Description

Technical Field

[0001] The present application relates to the technical field of recycling waste battery resources, and in particular to a method for recycling positive electrode materials of waste lithium cobalt oxide batteries. Background Art

[0002] With the rapid development of electric vehicles and renewable energy storage systems, demand for batteries has skyrocketed. However, batteries inevitably become obsolete after a few years of use. If not properly handled, these used batteries will result in a massive waste of resources and serious environmental pollution caused by solid waste. Batteries also contain a variety of valuable materials, such as cobalt, nickel, and lithium. Recycling these materials not only helps alleviate resource pressures but also reduces environmental pollution, achieving a win-win situation for both the economy and the environment. Therefore, the recycling of valuable metals from power batteries is of great significance to both comprehensive resource utilization and environmental protection.

[0003] Lithium cobalt oxide (LiCoO2) batteries are a common lithium-ion battery widely used in mobile devices, electric vehicles, and energy storage systems. Because they contain high-value metallic cobalt, they have high recycling value. In particular, using them as a cobalt source to prepare inexpensive, readily available, highly active, and highly stable functional materials is a forward-looking idea. However, there are relatively few studies on the use of cobalt metal extracted from spent LiCoO2 batteries to prepare nanofunctional materials, and most of the research focuses on cobalt oxides (such as Co3O4, CoO). Therefore, it is of great significance to further explore the potential applications of spent lithium cobalt oxide batteries in the preparation of functional materials and increase their added value applications.

[0004] In the article Journal of Material Cycles and Waste Management (2022) 24:425–432, the authors proposed and demonstrated the feasibility of preparing ZIF-67 materials from cobalt metal extracted from spent LiCoO2 batteries by precipitation of cobalt oxalate, providing a forward-looking approach to reducing the cost of raw materials for synthesizing ZIF-67 materials. However, the liquid-phase synthesis method used in this article produces a large amount of waste liquid, and due to the limited solubility of cobalt oxalate in water and alcohol, large-scale application is not possible.

[0005] In summary, how to achieve low-cost, efficient and environmentally friendly recycling of waste lithium cobalt oxide batteries remains a research focus and difficulty in the waste battery resource recycling industry. Summary of the Invention

[0006] The purpose of this application is to provide a new method for recycling the positive electrode materials of waste lithium cobalt oxide batteries.

[0007] This application adopts the following technical solutions:

[0008] One aspect of the present application discloses a method for recycling positive electrode materials of waste lithium cobalt oxide batteries, comprising: uniformly mixing positive electrode powder obtained from disassembling waste lithium cobalt oxide batteries with oxalic acid containing crystal water, reacting at 120-180°C for 1-5 hours, and after completion of the reaction, adding water to the reaction product for washing, filtering, and drying to obtain cobalt oxalate precipitate; uniformly mixing cobalt oxalate and 2-methylimidazole through ball milling, transferring the uniformly mixed powder to a reactor, and reacting at 60-150°C for 12-48 hours to obtain a metal-organic framework material ZIF-67.

[0009] It should be noted that the recycling method of the present application directly uses waste lithium cobalt oxide batteries to prepare metal-organic framework material ZIF-67, thereby recovering the cobalt valuable metal in the waste lithium cobalt oxide batteries. It not only solves the problem of environmental pollution and waste of valuable metal resources caused by the scrapping and discarding of waste lithium cobalt oxide batteries, but also recycles the cobalt metal resources in the waste lithium cobalt oxide batteries to prepare multifunctional metal-organic framework (MOF) material ZIF-67, realizing the added value of waste. In addition, the present application adopts a solid-solid reaction method to recover cobalt metal resources from waste lithium cobalt oxide batteries as a cobalt source, and a solvent-free crystallization method to synthesize the metal-organic framework (MOF) material ZIF-67. During the preparation process, only grinding, temperature control, and final drying treatment are used. Compared with the liquid phase synthesis method used in the prior art, the present application has the characteristics of simple process, low production cost, no generation of organic waste liquid, no pollution to the environment, and has the advantage of large-scale production.

[0010] In one implementation of the present application, the molar ratio of the positive electrode powder to the oxalic acid containing crystal water is 1:(2-20).

[0011] In one implementation of the present application, water is added for cleaning, specifically ultrasonic cleaning is used.

[0012] In one implementation of the present application, the rotation speed for uniform mixing by ball milling is 300-500 r / min, and the ball milling time is 5-10 min.

[0013] In one implementation of the present application, the molar ratio of cobalt oxalate to 2-methylimidazole is 1:(4-32).

[0014] Another aspect of the present application discloses a metal-organic framework material ZIF-67 prepared by the method of recycling the positive electrode material of waste lithium cobalt oxide batteries of the present application.

[0015] Another aspect of the present application discloses a method for recovering cobalt from the positive electrode material of waste lithium cobalt oxide batteries, comprising: uniformly mixing the positive electrode powder obtained from disassembling the waste lithium cobalt oxide batteries with oxalic acid containing crystalline water, reacting at 120-180° C. for 1-5 hours, and after the reaction is completed, adding water to the reaction product for washing, filtering, and drying to obtain a cobalt oxalate precipitate.

[0016] It should be noted that the method for recovering cobalt from waste lithium cobalt oxide battery positive electrode materials in the present application is actually the step of obtaining cobalt oxalate precipitate in the method for recycling waste lithium cobalt oxide battery positive electrode materials in the present application; therefore, its specific molar ratio, cleaning method, etc. can refer to the method for recycling waste lithium cobalt oxide battery positive electrode materials in the present application and are not specifically limited here.

[0017] Another aspect of the present application discloses cobalt oxalate prepared by the method of recovering cobalt from waste lithium cobalt oxide battery positive electrode materials.

[0018] The beneficial effects of this application are:

[0019] The method for recycling the positive electrode material of waste lithium cobalt oxide batteries of the present application uses the positive electrode material of waste lithium cobalt oxide batteries as a cobalt source to prepare the metal-organic framework material ZIF-67. The method has the characteristics of simple process, low production cost, no generation of organic waste liquid, no pollution to the environment, and the advantage of large-scale production. The method of the present application utilizes recycled waste lithium cobalt oxide batteries to prepare functional materials, realizes the reuse of waste and environmental protection, has important economic value and social benefits, and provides more ideas and solutions for increasing the added value application of waste batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the process of preparing the metal-organic framework material ZIF-67 from waste lithium cobalt oxide battery positive electrode materials in the embodiment of the present application. DETAILED DESCRIPTION

[0021] ZIF-67 is a metal organic framework (MOF) material. Due to its large specific surface area, porosity, adjustable structure, easy modification, and compound properties, it and its derivatives are widely used in the fields of electrode materials, electrocatalysts, and medicine by researchers. At present, the synthesis of ZIF-67 material is mainly based on the method of utilizing high-purity metal salt liquid phase synthesis. This method uses high-purity metal salts and a large amount of solvents and low productive rate in the building-up process, making the synthesis cost of ZIF-67 material high, thereby limiting its large-scale application. Therefore, how to simply and conveniently produce ZIF-67 material on a large scale remains the research focus and difficulty of this area. In the article Journal of Material Cycles and Waste Management (2022) 24:425–432, the authors proposed and demonstrated the possibility of preparing ZIF-67 from cobalt metal extracted from waste LiCoO2 batteries by cobalt oxalate precipitation, providing a forward-looking idea for reducing the raw material cost of synthesizing ZIF-67 materials. However, the liquid-phase synthesis method used in the article will produce a large amount of waste liquid, and due to the limited solubility of cobalt oxalate in water and alcohol, it cannot be applied on a large scale.

[0022] In view of this, the present application creatively adopts a solid-solid reaction method to recover cobalt metal resources from waste lithium cobalt oxide batteries as a cobalt source, and a solvent-free crystallization method to synthesize the metal-organic framework material ZIF-67. Figure 1 As shown, the method for recycling the positive electrode material of waste lithium cobalt oxide batteries of the present application includes mixing the positive electrode powder obtained from disassembling the waste lithium cobalt oxide batteries with oxalic acid containing crystalline water, reacting at 120-180°C for 1-5 hours, and after the reaction is completed, adding water to the reaction product for washing, filtering, and drying to obtain cobalt oxalate precipitate; ball-milling the cobalt oxalate and 2-methylimidazole to mix evenly, reacting at 60-150°C for 12-48 hours to obtain the metal-organic framework material ZIF-67.

[0023] Compared with the prior art, the method for recycling the positive electrode material of waste lithium cobalt oxide batteries in this application has the following advantages:

[0024] (1) Recycling the cobalt valuable metals in waste lithium cobalt oxide batteries not only solves the problem of environmental pollution and waste of valuable metal resources caused by waste lithium cobalt oxide batteries after they are scrapped and discarded, but also recycles the cobalt metal resources in waste lithium cobalt oxide batteries to prepare multifunctional metal-organic framework (MOF) material ZIF-67, realizing the added value utilization of waste, realizing waste reuse and environmental protection, which has important economic and social benefits and provides more ideas for increasing the added value application of waste batteries.

[0025] (2) The solid-solid reaction method is used to recover cobalt metal resources from waste lithium cobalt oxide batteries as a cobalt source, and the solvent-free crystallization method is used to synthesize the metal-organic framework (MOF) material ZIF-67. During the preparation process, only grinding, controlling a certain temperature, and drying treatment are used. Compared with the liquid phase preparation method, it has the advantages of simple process, low production cost, no generation of organic waste liquid, no pollution to the environment, and can be produced on a large scale.

[0026] The present invention is further described in detail below through specific examples and drawings. The following examples are only used to further illustrate the present invention and should not be construed as limiting the present invention.

[0027] Example 1

[0028] (1) After the used lithium cobalt oxide battery is fully discharged by soaking it in a 20% sodium chloride solution for 24 hours, it is disassembled to obtain the positive and negative electrode sheets. The positive electrode powder is then separated from the positive electrode sheet to obtain lithium cobalt oxide powder (LiCoO2), i.e., the positive electrode powder for standby use;

[0029] (2) Weigh 3 g of the lithium cobalt oxide powder (LiCoO2) recovered in step (1) and oxalic acid dihydrate (H2C2O4·2H2O) in a molar ratio of 1:5, grind and mix them evenly, transfer them to a hydrothermal reactor, heat to 150°C, and react for 2 h to obtain a sticky pink powder;

[0030] (3) adding water to the viscous powder in step (2), ultrasonically washing, filtering, and drying to obtain a pink cobalt oxalate precipitate for later use;

[0031] (4) 5 mmol of the cobalt oxalate precipitate in step (3) was mixed with 2-methylimidazole in a molar ratio of 1:4, placed in a ball mill, and automatically ground at a speed of 350 r / min for 5 min to obtain a mixed powder of cobalt oxalate and 2-methylimidazole;

[0032] (5) The mixed powder in step (4) was transferred to a reactor, placed in an oven, heated to 140°C, maintained for 12 hours, cooled to room temperature, washed with deionized water and ethanol, and vacuum dried to obtain the metal-organic framework material ZIF-67.

[0033] The product of step (5) was subjected to XRD and BET characterization tests; wherein, the BET characterization test was performed using a static volumetric flask method. The results showed that the obtained product was ZIF-67 with a yield of 92% and a specific surface area of 1120 m 2 / g.

[0034] The pink cobalt oxalate precipitate from step (3) was weighed, and after the viscous sample from step (3) was immersed in water, the leachate solution and the precipitate were subjected to ICP testing to test the cobalt content. The recovery rate of cobalt in the cobalt oxalate precipitate was calculated as follows: P = m*w% / (CV+m*w%); where P is the recovery rate of cobalt in the cobalt oxalate, m is the mass of the solid powder after immersion in water, w% is the cobalt content in the solid powder, C is the concentration of cobalt in the solution, and V is the volume of the leachate. After calculation, the cobalt recovery rate in this example was 99.0%.

[0035] Based on the above experiments, this example further tested different molar ratios of lithium cobaltate powder to oxalic acid dihydrate and measured the cobalt recovery rates of the cobalt oxalate prepared under these different molar ratios and reaction temperature and time conditions. The specific molar ratios, temperatures, and time conditions, and their corresponding cobalt recoveries, are shown in Table 1.

[0036] Table 1 Cobalt recovery of cobalt oxalate prepared under different conditions

[0037] molar ratio Reaction temperature Reaction time Cobalt recovery rate Test 1 1:2 120℃ 2h 80.5％ Test 2 1:2 150℃ 2h 83.5％ Test 3 1:10 150℃ 5h 95.5％ Test 4 1:20 150℃ 1h 94.6％ Test 5 1:5 180℃ 2h 98.6％

[0038] In Table 1, the molar ratio is the molar ratio of lithium cobaltate powder to oxalic acid dihydrate, and the reaction temperature and reaction time are the heating temperature and reaction time in the hydrothermal reactor in step (2).

[0039] The results in Table 1 show that the recovery of cobalt oxalate can be achieved when the molar ratio of lithium cobaltate powder to oxalic acid dihydrate is 1:(2-20); however, the cobalt recovery rate is higher when the molar ratio of the two is 1:(5-20), reaching more than 90%. In particular, the recovery rate of cobalt metal reaches the maximum when the molar ratio of the two is 1:5.

[0040] Example 2

[0041] (1) After the used lithium cobalt oxide battery is fully discharged by soaking it in a 20% sodium chloride solution for 24 hours, it is disassembled to obtain the positive and negative electrode sheets, and then the positive electrode powder is separated from the positive electrode sheet to obtain lithium cobalt oxide powder (LiCoO2) for standby use;

[0042] (2) Weigh 3 g of the lithium cobalt oxide powder recovered in step (1) and oxalic acid dihydrate (H2C2O4·2H2O) in a molar ratio of 1:5, grind and mix them evenly, transfer them to a hydrothermal reactor, heat to 150°C, and react for 2 h to obtain a sticky pink powder;

[0043] (3) ultrasonically washing and drying the viscous powder in step (2) to obtain a pink cobalt oxalate precipitate for later use;

[0044] (4) 3 mmol of the cobalt oxalate dihydrate precipitate in step (3) and 2-methylimidazole were mixed in a ratio of 1:8, placed in a ball mill, and automatically ground at a speed of 400 r / min for 5 min to obtain a mixed powder of cobalt oxalate and 2-methylimidazole;

[0045] (5) The mixed powder in step (4) was transferred to a reactor, placed in an oven, heated to 150°C, maintained for 24 hours, cooled to room temperature, washed with deionized water and ethanol, and vacuum dried to obtain a metal-organic framework material ZIF-67.

[0046] The product of step (5) was tested in the same manner as in Example 1 to confirm that the metal-organic framework material ZIF-67 was indeed prepared in this example with a yield of 95% and a specific surface area of 1335 m 2 / g.

[0047] Example 3

[0048] (1) After the used lithium cobalt oxide battery is fully discharged by soaking it in a 20% sodium chloride solution for 24 hours, it is disassembled to obtain the positive and negative electrode sheets, and then the positive electrode powder is separated from the positive electrode sheet to obtain lithium cobalt oxide powder (LiCoO2) for standby use;

[0049] (2) Weigh 3 g of the lithium cobalt oxide powder recovered in step (1) and oxalic acid dihydrate (H2C2O4·2H2O) in a molar ratio of 1:5, grind and mix them evenly, transfer them to a hydrothermal reactor, heat to 150°C, and react for 2 h to obtain a sticky pink powder;

[0050] (3) ultrasonically washing and drying the viscous powder in step (2) to obtain a pink cobalt oxalate precipitate for later use;

[0051] (4) 1 mmol of the cobalt oxalate dihydrate precipitate in step (3) and 2-methylimidazole were mixed in a ratio of 1:32, placed in a ball mill, and automatically ground at a speed of 500 r / min for 10 min to obtain a mixed powder of cobalt oxalate and 2-methylimidazole;

[0052] (5) The mixed powder in step (4) was transferred to a reactor, placed in an oven, heated to 150°C, maintained for 24 hours, cooled to room temperature, washed with deionized water and ethanol, and vacuum dried to obtain a metal-organic framework material ZIF-67.

[0053] The product of step (5) was tested in the same manner as in Example 1 to confirm that the metal-organic framework material ZIF-67 was indeed prepared in this example with a yield of 96% and a specific surface area of 1267 m 2 / g.

[0054] Example 4

[0055] (1) After the used lithium cobalt oxide battery is fully discharged by soaking it in a 20% sodium chloride solution for 24 hours, it is disassembled to obtain the positive and negative electrode sheets, and then the positive electrode powder is separated from the positive electrode sheet to obtain lithium cobalt oxide powder (LiCoO2) for standby use;

[0056] (2) Weigh 3 g of the lithium cobalt oxide powder recovered in step (1) and oxalic acid dihydrate (H2C2O4·2H2O) in a molar ratio of 1:5, grind and mix them evenly, transfer them to a hydrothermal reactor, heat to 150°C, and react for 2 h to obtain a sticky pink powder;

[0057] (3) ultrasonically washing and drying the viscous powder in step (2) to obtain a pink cobalt oxalate precipitate for later use;

[0058] (4) 5 mmol of the cobalt oxalate precipitate in step (3) and 2-methylimidazole were mixed in a ratio of 1:2, placed in a ball mill, and automatically ground at a speed of 350 r / min for 8 min to obtain a mixed powder of cobalt oxalate and 2-methylimidazole;

[0059] (5) The mixed powder in step (4) was transferred to a reactor, placed in an oven, heated to 60°C, maintained for 48 hours, cooled to room temperature, washed with deionized water and ethanol, and vacuum dried to obtain a metal-organic framework material ZIF-67.

[0060] The product of step (5) was tested in the same manner as in Example 1 to confirm that the metal-organic framework material ZIF-67 was indeed prepared in this example with a yield of 90% and a specific surface area of 1023 m 2 / g.

[0061] Comparative analysis of Example 1 to Example 4 shows that the molar ratio of cobalt oxalate and 2-methylimidazole is 1: (4-32) and after ball milling for 5-10min at 300-500r / min, the reaction is carried out at 60-150°C for 12-48h to obtain the desired metal-organic framework material ZIF-67. However, when the amount of 2-methylimidazole is low, such as when the molar ratio of cobalt oxalate and 2-methylimidazole in Example 4 is 1: 2, the yield of the metal-organic framework material ZIF-67 is low. As for the reaction temperature and reaction time, in principle, within the range of 60-150°C, the lower the temperature, the longer the reaction time required, for example, the reaction is carried out at 60°C for 48 hours and at 150°C for 12 hours.

[0062] The above content is a further detailed description of the present application in conjunction with specific implementation methods, and the specific implementation of the present application cannot be considered to be limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application.

Claims

1. A method for recycling waste lithium cobalt oxide battery cathode materials, characterized by: The method includes: uniformly mixing cathode powder obtained from dismantling waste lithium cobalt oxide batteries with oxalic acid containing crystal water, reacting at 120-180°C for 1-5 hours, and after the reaction is completed, adding water to the reaction product for washing, filtering, and drying to obtain cobalt oxalate precipitate; uniformly mixing cobalt oxalate and 2-methylimidazole through ball milling, and reacting at 60-150°C for 12-48 hours to obtain a metal-organic framework material ZIF-67.

2. The method according to claim 1, wherein: The molar ratio of the positive electrode powder to the oxalic acid containing crystal water is 1:(2-20).

3. The method according to claim 1, wherein: The adding of water for cleaning specifically adopts ultrasonic cleaning.

4. The method according to claim 1, wherein: The ball milling mixing is carried out at a rotation speed of 300-500 r / min, and the ball milling time is 5-10 min.

5. The method according to any one of claims 1 to 4, characterized in that: The molar ratio of the cobalt oxalate to 2-methylimidazole is 1:(4-32).

6. The metal-organic framework material ZIF-67 prepared by the method according to any one of claims 1 to 5.

7. A method for recovering cobalt from waste lithium cobalt oxide battery cathode materials, characterized in that: The method comprises the steps of uniformly mixing cathode powder obtained from dismantling waste lithium cobalt oxide batteries with oxalic acid containing crystal water, reacting the mixture at 120-180° C. for 1-5 hours, and after the reaction is completed, adding water to the reaction product for washing, filtering, and drying to obtain cobalt oxalate precipitate.

8. The method according to claim 7, wherein: The molar ratio of the positive electrode powder to the oxalic acid containing crystal water is 1:(2-20).

9. The method according to claim 7 or 8, characterized in that: The adding of water for cleaning specifically adopts ultrasonic cleaning.

10. Cobalt oxalate prepared by the method according to any one of claims 7 to 9.

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