Preparation method and application of ternary MOF based on waste lithium battery oxide derivation

Abstract

The invention relates to the technical field of waste plastic recovery and electrochemical energy storage, and discloses a preparation method and application of a ternary MOF based on waste lithium battery oxide derivation, and the preparation method comprises the following steps: step 1, taking a waste PET plastic bottle as an organic ligand precursor, taking a nickel cobalt manganese oxide obtained by disassembling a waste ternary lithium battery as a metal source, and adding N, N-dimethyl formamide into the organic ligand precursor; adding nitric acid into a N, N-dimethylformamide / water mixed solvent to adjust the acidity and promote the leaching of metal ions; according to the preparation method and application of the ternary MOF based on waste lithium battery oxide derivation, a waste PET plastic bottle is used as an organic ligand precursor to be combined with nickel-cobalt-manganese oxide in a waste ternary lithium battery, the ternary MOF is directly synthesized through a hydrothermal method, high-value utilization of two types of typical solid waste is achieved, and the method is suitable for industrial production. Valuable metals such as nickel, cobalt and manganese in the waste lithium battery are efficiently recycled, and the metal leaching and coordination efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of waste plastic recycling and electrochemical energy storage technology, specifically to a method for preparing ternary MOFs derived from waste lithium battery oxides and their applications. Background Technology

[0002] Waste PET plastic bottles and used ternary lithium batteries are two types of typical solid waste recognized in the global environmental governance field. Although they can be mechanically recycled and reshaped, this method can only achieve downgrading and cannot return them to high-value applications. A large amount of unrecycled PET has a degradation cycle of up to hundreds of years in the natural environment, which can easily cause soil and water pollution. At the same time, with the rapid development of new energy vehicles and energy storage industries, the annual amount of retired ternary lithium batteries has surged. Although the valuable metals such as nickel, cobalt, and manganese contained in them have recycling value, traditional recycling technologies have obvious limitations. Existing recycling methods are inefficient and pose potential environmental pollution risks. Therefore, how to combine these two types of waste for resource utilization, especially in the field of electrochemical energy storage, has become an urgent problem to be solved.

[0003] Supercapacitors, as a high-power and high-stability energy storage device, have wide applications in electric vehicles, renewable energy, and other fields. Their performance mainly depends on the structure and properties of the electrode materials. Among them, MOF, also known as metal-organic framework materials, has become a research hotspot for capacitor electrode materials in recent years due to its high specific surface area, good pore structure and metal active sites. Combining MOF with waste can not only improve battery performance, but also effectively promote waste resource utilization.

[0004] Existing waste recycling technologies mostly target single types of waste, such as recycling only PET or only lithium battery metals, without considering the compatibility of the chemical properties of the two types of waste. That is, PET can be degraded into organic ligands and lithium battery oxides can provide metal sources, which leads to limited resource utilization. Furthermore, MOFs synthesized by traditional methods have poor conductivity, requiring the addition of a large amount of conductive agents to meet electrode requirements. Moreover, MOFs are prone to framework collapse during charge and discharge, resulting in insufficient cycle stability.

[0005] To address the aforementioned issues, there is an urgent need for innovative designs based on existing metal-organic framework materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing ternary MOFs derived from waste lithium battery oxides and their applications, in order to solve the problems mentioned in the background art. Existing waste recycling technologies are mostly aimed at single wastes, only recycling PET or only recycling lithium battery metals, without considering the chemical property matching between the two types of wastes. That is, PET can be degraded into organic ligands and lithium battery oxides can provide metal sources, resulting in limited resource utilization. In addition, MOFs synthesized by traditional methods have poor conductivity, requiring the addition of a large amount of conductive agent to meet electrode requirements. Furthermore, MOFs are prone to framework collapse during charge and discharge, resulting in insufficient cycle stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing ternary MOFs derived from waste lithium battery oxides and its application, comprising the following steps: Step 1: Using waste PET plastic bottles as organic ligand precursors and nickel cobalt manganese oxide obtained from the dismantling of waste ternary lithium batteries as metal source, nitric acid is added to N,N-dimethylformamide / water mixed solvent to adjust acidity and promote metal ion leaching. Step 2: The obtained mixture is transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor for hydrothermal reaction. After the reaction, it is washed and dried to obtain a ternary metal-organic framework material containing a Ni / Co / Mn-terephthalate skeleton. Step 3: Use the synthesized ternary metal-organic framework material as the electrode material of the supercapacitor to improve capacitance performance.

[0008] By adopting the above technical solution, ternary MOFs are prepared by co-processing waste PET and waste lithium battery NCM and used for supercapacitor electrodes, realizing the high-value recycling of two types of waste. At the same time, it provides a preparation path for high-performance electrode materials, solving the problems of low recycling efficiency and high cost of electrode materials in traditional waste recycling.

[0009] Preferably, the mass ratio of nickel cobalt manganese oxide from the dismantling of waste ternary lithium batteries in step 1 to waste PET plastic is 0.05–2.2:1, and the volume ratio of N,N-dimethylformamide to water in step 1 is 1–8:1.

[0010] By adopting the above technical solution, the mass ratio of NCM to PET is limited to ensure the appropriate ratio of metal source and organic ligand, thus guaranteeing the synthesis efficiency and structural stability of MOF, avoiding raw material waste or incomplete reaction, and clarifying the hydrothermal reaction temperature and time range. This allows for flexible control of MOF crystallinity and morphology to meet different performance requirements and ensure that the synthesized product has a good pore structure.

[0011] Preferably, in step 1, the mass ratio of nitric acid to nickel cobalt manganese oxide is 0.01–0.60:1, and the molar ratio of the provided protons to the total molar ratio of Ni, Co and Mn is 0.5–5:1. The pH of the solution before the reaction is 1.0–5.0, and the nitric acid is calculated as pure HNO3.

[0012] By adopting the above technical solution, limiting the volume ratio of DMF to water, optimizing the mixed solvent system, promoting the leaching of NCM metal ions and the degradation of PET, ensuring the uniformity of the reaction, and laying the foundation for the excellent structure of MOF.

[0013] Preferably, the hydrothermal reaction temperature in step 2 is 120–260°C, and the reaction time is 8–30 hours.

[0014] By adopting the above technical solution, the amount of nitric acid, the proton molar ratio and pH are standardized to achieve efficient leaching of metal ions and avoid interference from impurities, ensuring uniform metal composition of MOF and improving electrochemical activity.

[0015] Preferably, the N,N-dimethylformamide / water mixed solvent in step 1 can be replaced by NMP, DMAC, DEF or ethylene glycol / water system.

[0016] By adopting the above technical solution, multiple alternative solvents for DMF are provided, increasing the flexibility of solvent selection, adapting to different production conditions, reducing the process's dependence on a single solvent, and improving industrial applicability.

[0017] Preferably, the ratio of the PET plastic solid and the nickel cobalt manganese oxide solid to the solvent is 1:20–80 (g:mL), and the obtained PET plastic solid and nickel cobalt manganese oxide solid are washed sequentially with DMF, ethanol and deionized water, and then vacuum dried at 60–120°C for 6–12 h.

[0018] By adopting the above technical solution, the solid-liquid ratio and post-treatment conditions are limited to ensure that the reaction proceeds fully. At the same time, impurities are removed by washing and drying to improve the purity and structural stability of MOF and ensure consistent performance.

[0019] A ternary MOF derived from waste lithium battery oxides, wherein the metal molar ratio Ni:Co:Mn = 1:(0.5–1.5):(0.5–1.5), and the BET specific surface area is ≥600 m². 2 / g, total pore volume ≥0.4cm³ 3 / g, with morphology of plate-like, rod-like or flower-like secondary assemblies, and average characteristic size of 50–500 nm.

[0020] By adopting the above technical solution, the MOF parameters are clearly defined, ensuring that the material has a high specific surface area, abundant active sites and suitable morphology, providing structural support for supercapacity and high performance.

[0021] A supercapacitor electrode sheet, which is obtained by further processing the ternary MOF prepared above, includes a current collector and an electrode active layer coated thereon. The electrode active layer is composed of ternary MOF (80-90% by mass), conductive agent (2-10% by mass), and binder (2-10% by mass), and is suitable for alkaline or neutral electrolytes. The conductive agent and binder are composed in a mass ratio of 8:1:1, and are suitable for alkaline or neutral electrolytes.

[0022] By adopting the above technical solution, the composition of the electrode sheet and the applicable electrolyte are defined, and the active material, conductivity and adhesion are balanced, so that the electrode sheet is easy to form, has good conductivity, and is suitable for alkaline or neutral supercapacitive systems.

[0023] Preferably, the electrode sheet has a specific capacitance ≥1000 in a 2M KOH three-electrode system and a current density of 1, and a specific capacitance retention rate ≥80% at 15.

[0024] By adopting the above technical solution, the specific capacitance and retention rate of the electrode sheet are limited, ensuring that the electrode has excellent performance under both high and low current densities, thus meeting the requirements of high capacity and high rate for ultracapacitors.

[0025] An asymmetric two-electrode supercapacitor, wherein at least one electrode comprises the supercapacitor electrode sheet described above, and the other electrode is a carbon-based electrode, the device having an energy density ≥25 and a corresponding power density ≥1700.

[0026] By adopting the above technical solution, the asymmetric supercapacitor structure and performance are clearly defined, achieving a balance between high energy and high power, and making it suitable for high-end scenarios such as electric vehicles and energy storage power stations.

[0027] Compared with the prior art, the beneficial effects of the present invention are: the preparation method of ternary MOF derived from waste lithium battery oxide and its application: 1. By combining waste PET plastic bottles as organic ligand precursors with nickel, cobalt, and manganese oxides from waste ternary lithium batteries, ternary MOFs are directly synthesized via a hydrothermal method. This method achieves high-value utilization of two typical types of solid waste, efficiently recovering valuable metals such as nickel, cobalt, and manganese from waste lithium batteries with significantly improved metal leaching and coordination efficiency, and avoiding the downgraded recycling of PET plastics. The structure and morphology of MOFs can be precisely adjusted by controlling the reaction temperature, reaction time, and precursor mass ratio, ultimately obtaining high-performance electrode materials that meet the requirements of supercapacitors. This effectively solves the dual problems of low recycling efficiency and high environmental pollution of traditional wastes, as well as the high cost of raw materials for high-performance electrode materials in the electrochemical field. 2. Furthermore, the innovative approach of using waste PET as a ligand precursor not only reduces environmental pollution from plastic waste but also provides more cost-effective materials for the field of electrochemical energy storage. The synthesized MOF has a high specific surface area, abundant pore structure, and metal active sites, which can provide a good channel for the rapid diffusion of electrolyte ions while maintaining good electrochemical stability and durability. In practical applications, this technology effectively improves the energy density and power density of supercapacitors. Attached Figure Description

[0028] Figure 1 The X-ray diffraction pattern of the ternary MOF structure of Ni / Co / Mn terephthalate obtained in Example 1 of this invention; Figure 2 This is a scanning electron microscope image of the ternary MOF skeleton of Ni / Co / Mn terephthalate obtained in Example 1 of the present invention. Figure 3 The galvanostatic charge-discharge (GCD) curves of the material in Example 1 under a three-electrode system are shown. Figure 4 This is an exploded structural diagram of the asymmetric two-electrode capacitor device in Example 1; Figure 5 The constant current charge-discharge (GCD) curves of the asymmetric two-electrode capacitor device in Example 1 are shown. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figures 1-5 This invention provides a technical solution: a method for preparing ternary MOFs derived from waste lithium battery oxides and its application; Example 1: Step 1: In this embodiment, 2.00g of cleaned and dried waste PET fragments and 0.80g of NCM powder from waste batteries are premixed in a mixed solvent of 80mL N,N-dimethylformamide and 20mL deionized water for 10min. After adding 0.24g of 68% nitric acid, the mixture is stirred for another 30min to bring the apparent pH to approximately 2.2 at room temperature and then NCM leaching is initiated. Step 2: The reaction slurry was transferred to a 100mL polytetrafluoroethylene-lined hydrothermal reactor and reacted at 180℃ for 16h. The mixture was then naturally cooled to room temperature. After centrifugation, the product was washed three times each with DMF, anhydrous ethanol and deionized water, and then vacuum dried at 80℃ for 8h to obtain 2.18g of light green powder. Characterization of ternary MOF (metal-organic framework) materials: The molar ratio of the metals, as determined by ICP-OES, was Ni:Co:Mn = 1:0.92:0.84. N2 adsorption showed that the BET specific surface area was 720·m² and the total pore volume was 0.52·m². The XRD pattern shows characteristic diffraction peaks of terephthalate-type MOFs, such as Figure 1 As shown; SEM images revealed a morphology dominated by rods ranging from 100 to 300 nm, such as... Figure 2 As shown; The ternary MOF with Ni / Co / Mn terephthalate framework prepared in the above steps was used as the active material. It was mixed with acetylene black and PTFE in ethanol at a ratio of 8:1:1 and ultrasonically prepared for 30 min. The slurry was then coated onto nickel foam pretreated with 3M HCl. The final loading was controlled to be 2.0. Three-electrode testing was conducted in 2M KOH, using Hg / HgO as a reference and a platinum sheet as the counter electrode. The operating potential window was set to 0-0.5V (vs. Hg / HgO). For two-electrode asymmetric devices, PVA / KOH gel electrolyte was used, and the device operating voltage was 0-1.6V. In a 2M KOH three-electrode system, the sample exhibited a specific capacitance of approximately 1150 A at 1 A and retained approximately 84% of its specific capacitance at 15 A; the corresponding GCD curve is shown below. Figure 3 As shown; In the asymmetric two-electrode device of PVA / KOH gel electrolyte, its structural schematic diagram is shown below. Figure 4 The calculated energy density is 27, corresponding to a power density of approximately 1800. The GCD curve is shown below. Figure 5 As shown.

[0031] Example 2: Step 1: In this embodiment, 1.50g of cleaned and dried waste PET fragments and 0.30g of NCM powder from waste batteries are premixed in a mixed solvent of 60mL N-methylpyrrolidone (NMP) and 20mL deionized water for 10min. After adding 0.18g of 68% nitric acid, the mixture is stirred for another 40min to bring the apparent pH to approximately 1.6 at room temperature and then NCM leaching is initiated. Step 2: The reaction slurry was transferred to a 100mL PTFE-lined hydrothermal reactor and reacted at 200℃ for 12h. The mixture was then naturally cooled to room temperature. After centrifugation, the product was washed three times each with DMF, anhydrous ethanol and deionized water, and then vacuum dried at 90℃ for 10h to obtain 1.63g of light green powder. Ternary MOF characterization: The molar ratio of metals in the material, as determined by ICP-OES, is Ni:Co:Mn = 1:1.10:0.60, which is within the composition range of the claims. N2 adsorption tests showed that the material had a BET specific surface area of ​​650 and a total pore volume of 0.45. The XRD pattern shows characteristic diffraction peaks of terephthalate type MOF, which are sharper than those in Example 1; SEM images revealed a morphology dominated by 80–200 nm nanorods / short rods with clustered growth. The ternary MOF with Ni / Co / Mn terephthalate framework prepared in the above steps was used as the active material. It was mixed with acetylene black and PTFE in ethanol at a ratio of 8:1:1 and ultrasonically prepared for 30 min. The slurry was then coated onto nickel foam pretreated with 3MHCl, and the final loading was controlled to be 2.0. Three-electrode testing was conducted in 2M KOH, using Hg / HgO as a reference and a platinum sheet as the counter electrode. The operating potential window was set to 0-0.5V (vs. Hg / HgO). For two-electrode asymmetric devices, PVA / KOH gel electrolyte was used, and the device operating voltage was 0-1.6V. The specific capacitances of the Ni / Co / Mn terephthalate framework ternary MOF are 980 and 804 at 1 A and 15 A, respectively, with a capacitance retention of 82%. The ternary MOF with a Ni / Co / Mn terephthalate framework has an energy density of 25.5 Wh· and a corresponding power density of 1730 W· in a two-electrode capacitor. In a three-electrode system with 2M KOH, the specific capacitance of the sample at 1A is approximately 1050F, and it exhibits a specific capacitance retention of approximately 81% at 15A. In the asymmetric two-electrode device with PVA / KOH gel electrolyte, the calculated energy density is approximately 25.5, and the corresponding power density is 1730. Regarding the amount of raw materials and the selection of solvents, Example 1 used 2.00g of waste PET fragments and 0.80g of waste lithium battery NCM powder, with a mass ratio of 0.4:1, and the solvent was a mixture of 80mL N,N-dimethylformamide and 20mL deionized water. Example 2 used 1.50g of waste PET fragments and 0.30g of NCM powder, with the mass ratio reduced to 0.2:1, and the solvent was replaced with a mixture of 60mL N-methylpyrrolidone and 20mL deionized water. Regarding the adjustment parameters of the reaction system, in Example 1, 0.24g of 68% nitric acid was added to adjust the apparent pH at room temperature to about 2.2, and the mixture was premixed and stirred for 30 minutes to initiate NCM leaching. In Example 2, the amount of 68% nitric acid added was reduced to 0.18g, the pH was reduced to about 1.6, and the premixing and stirring time was extended to 40 minutes. Regarding the hydrothermal reaction and post-treatment conditions, the hydrothermal reaction temperature of Example 1 was 180°C, the reaction time was 16 hours, and the product drying conditions were 80°C vacuum drying for 8 hours. In Example 2, the hydrothermal temperature was increased to 200°C, the reaction time was shortened to 12 hours, and the drying conditions were adjusted to 90°C vacuum drying for 10 hours. Regarding the MOF characterization results, the MOF synthesized in Example 1 had a metal molar ratio of Ni:Co:Mn = 1:0.92:0.84, a BET specific surface area of ​​720, a total pore volume of 0.52, and exhibited a single rod-like morphology of 100-300 nm under scanning electron microscopy. The characteristic peaks of X-ray diffraction were clear. In contrast, the MOF of Example 1 had a metal molar ratio of Ni:Co:Mn = 1:1.10:0.60, a reduced BET specific surface area of ​​650, a total pore volume of 0.45, and exhibited nanorods / short rods of 80-200 nm with clustering under SEM. The characteristic peaks of XRD were sharper than those of Example 1. In terms of electrochemical performance indicators, in the three-electrode system, the MOF electrode of Example 1 has a specific capacitance of 1150 at a current density of 1 and a capacitance retention rate of 84% at 15. Under the same test conditions, the MOF electrode of Example 2 has a specific capacitance of 1050 and a capacitance retention rate of 81% at 15. In the asymmetric two-electrode device test, the device energy density of Example 1 is 27 and the corresponding power density is 1800. The device in Example 2 has an energy density of 25.5 and a corresponding power density of 1730, and its overall electrochemical performance is slightly lower than that in Example 1.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing ternary MOFs derived from waste lithium battery oxides, characterized in that, Includes the following steps: Step 1: Using waste PET plastic bottles as organic ligand precursors and nickel cobalt manganese oxide obtained from the dismantling of waste ternary lithium batteries as metal source, nitric acid is added to N,N-dimethylformamide / water mixed solvent to adjust acidity and promote metal ion leaching. Step 2: The obtained mixture is transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor for hydrothermal reaction. After the reaction, it is washed and dried to obtain a ternary metal-organic framework material containing a Ni / Co / Mn-terephthalate skeleton. Step 3: Use the synthesized ternary metal-organic framework material as the electrode material of the supercapacitor to improve capacitance performance.

2. The method for preparing ternary MOFs based on waste lithium battery oxides according to claim 1, characterized in that: In step 1, the mass ratio of nickel cobalt manganese oxide from the dismantled waste ternary lithium batteries to waste PET plastic is 0.05–2.2:1, and the volume ratio of N,N-dimethylformamide to water in step 1 is 1–8:

1.

3. The method for preparing ternary MOFs based on waste lithium battery oxides according to claim 1, characterized in that: In step 1, the mass ratio of nitric acid to nickel cobalt manganese oxide is 0.01–0.60:1, and the molar ratio of the provided protons to the total molar ratio of Ni, Co and Mn is 0.5–5:

1. The pH of the solution before the reaction is 1.0–5.0, and the nitric acid is calculated as pure HNO3.

4. The method for preparing ternary MOFs based on waste lithium battery oxides according to claim 1, characterized in that: The hydrothermal reaction temperature in step 2 is 120–260℃, and the reaction time is 8–30 hours.

5. The method for preparing ternary MOFs based on waste lithium battery oxides according to claim 1, characterized in that: The N,N-dimethylformamide / water mixed solvent in step 1 can be replaced with NMP, DMAC, DEF, or an ethylene glycol / water system.

6. The method for preparing ternary MOFs based on waste lithium battery oxides according to claim 1, characterized in that: The ratio of the PET plastic solids and nickel cobalt manganese oxide solids to the solvent is 1:20–80 (g:mL), and the obtained PET plastic solids and nickel cobalt manganese oxide solids are washed sequentially with DMF, ethanol and deionized water, and then vacuum dried at 60–120℃ for 6–12h.

7. A ternary MOF derived from waste lithium battery oxide, characterized in that: Prepared by any one of claims 1-6, wherein the metal molar ratio Ni:Co:Mn = 1:(0.5–1.5):(0.5–1.5), and the BET specific surface area is ≥600 m². 2 / g, total pore volume ≥0.4cm³ 3 / g, with morphology of plate-like, rod-like or flower-like secondary assemblies, and average characteristic size of 50–500 nm.

8. A supercapacitor electrode sheet, characterized in that: The electrode sheet obtained by further processing the ternary MOF prepared according to claim 7 includes a current collector and an electrode active layer coated thereon. The electrode active layer is composed of ternary MOF (80-90% by mass), conductive agent (2-10% by mass) and binder (2-10% by mass), and is suitable for alkaline or neutral electrolytes.

9. A supercapacitor electrode sheet according to claim 8, characterized in that: The electrode sheet has a specific capacitance ≥1000 in a 2M KOH three-electrode system and a current density of 1, and a specific capacitance retention rate ≥80% at 15.

10. An asymmetric two-electrode supercapacitor, characterized in that: At least one electrode comprises the supercapacitor electrode sheet as described in claim 9, and the other electrode is a carbon-based electrode. The device has an energy density ≥25 and a corresponding power density ≥1700.

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