Method for hydro-thermal synthesis of metal organic framework by using waste lithium ion battery leachate

Abstract

The invention relates to the technical field of metal organic materials, in particular to a method for hydro-thermal synthesis of a metal organic framework by using a waste lithium ion battery lixivium, which comprises the following steps: firstly, carrying out discharge, disassembly, ultrasonic separation, calcination and ball milling treatment on a waste lithium cobalt oxide battery to obtain lithium cobalt oxide powder; preparing a 2-6 mol / L acetic acid solution, mixing the acetic acid solution with the powder, adding a hydrogen peroxide reducing agent, heating, stirring and leaching to obtain a leaching solution containing cobalt acetate; adding trimesic acid into the leachate, and heating and stirring to prepare a mixed solution; and transferring the mixed solution into a hydrothermal kettle for reaction, and filtering, washing and drying to obtain Co3 (BTC) 2. 12H2O. According to the method, waste battery recycling and MOF material preparation are combined, cobalt acetate in a waste battery leaching solution serves as a metal node, trimesic acid serves as an organic ligand, and MOF is subjected to hydro-thermal synthesis. The method has the advantages of mild process conditions, realization of high-value utilization of cobalt resources in waste batteries, reduction of environmental pollution, reduction of the preparation cost of the MOF material, high product purity and crystallinity, and wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of metal-organic materials technology, specifically a method for hydrothermal synthesis of metal-organic frameworks using leachate from waste lithium-ion batteries. Background Technology

[0002] With the rapid development of new energy vehicles, energy storage systems, and portable electronic devices, lithium-ion batteries, with their outstanding advantages such as high energy density and long cycle life, have been applied on an unprecedented scale in various end products, becoming a core basic component supporting the development of related industries. However, the rapid expansion of the industry has also brought significant follow-up challenges. Early lithium-ion batteries have gradually entered their end-of-life cycle, and coupled with the accelerated pace of electronic device upgrades, a large number of waste lithium-ion batteries are constantly being generated, forming a massive and rapidly growing wave of waste batteries. Their proper disposal and efficient utilization have become an urgent problem facing the industry.

[0003] Discarded lithium-ion batteries have a complex composition, containing various substances that pose potential hazards to the ecological environment and public health. If not properly disposed of, harmful substances such as heavy metals, toxic electrolytes, and fluorides inside the batteries can easily leak into the natural environment. Once seeped into the soil, they can cause excessive levels of heavy metals, pollute groundwater and surface water, and disrupt the ecological balance of aquatic bodies. These harmful substances are not only difficult to degrade naturally, but may also accumulate through the food chain, posing a long-term threat to plant and animal growth and human health, leading to serious environmental safety problems.

[0004] Lithium-ion batteries, especially lithium cobalt oxide batteries, are rich in lithium and cobalt, metals that are scarce strategic resources with extremely high recycling value and are known as valuable urban minerals. However, the industry currently still relies on traditional landfill or incineration methods for disposing of used lithium-ion batteries. These methods cannot effectively recover valuable metals, resulting in a huge waste of strategic resources and further exacerbating the environmental burden. This runs counter to the global consensus on green and sustainable development and is inconsistent with the industrial development trend of resource recycling.

[0005] Metal-organic frameworks (MOFs) are a class of porous crystalline materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. They possess excellent properties such as high designability, ultra-large specific surface area, and tunable pore environment, showing broad application prospects in adsorption separation, catalytic reactions, and gas storage. Currently, the synthesis of MOF materials largely relies on pure metal salts as precursors, resulting in high raw material costs. Furthermore, the resource recycling of spent lithium-ion batteries is mostly limited to the refining of single metal elements, leading to relatively simple recycling pathways and low added value. Therefore, utilizing leachate from spent lithium-ion batteries to synthesize MOFs offers a new approach to solving these problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for hydrothermal synthesis of metal-organic frameworks using leachate from waste lithium-ion batteries, in order to solve the problems mentioned in the background art, such as environmental pollution and resource waste caused by improper disposal of waste lithium-ion batteries, and the high cost caused by the reliance on pure metal salts in the synthesis of traditional metal-organic framework materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries includes the following steps: (1) Raw material preparation: After the waste lithium-ion batteries are discharged, disassembled and separated, and the cathode is specially treated, high-purity lithium cobalt oxide LiCoO2 powder cathode material is obtained; (2) Solution preparation: Measure the acetic acid reagent, add deionized water and stir evenly to prepare an acetic acid solution with a concentration of 2-6 mol / L; (3) Leaching reaction: The lithium cobalt oxide powder obtained in step (1) is mixed with the acetic acid solution prepared in step (2) in proportion, and hydrogen peroxide H2O2 is added as a reducing agent. The mixture is heated and stirred at 50-80℃ for 40-90 min. After the reaction is completed, the mixture is filtered and the leachate containing cobalt acetate Co(Ac)2 is collected. (4) Preparation of mixed solution: Add organic ligand pyromellitic acid solid powder to the leachate obtained in step (3), heat and stir at 40-60°C to completely dissolve pyromellitic acid and obtain a uniform mixed solution; (5) Hydrothermal reaction: The mixed solution obtained in step (4) is transferred to a hydrothermal reactor with a polytetrafluoroethylene liner. After sealing and assembly, the hydrothermal reaction is carried out at 120-135℃ for 12-48h. After the reaction is completed, the hydrothermal reactor is naturally cooled to room temperature. (6) Washing and drying: The solid product after hydrothermal reaction is filtered and separated, washed and dried to finally obtain the metal-organic framework material Co3(BTC)2·12H2O.

[0008] As a preferred method, the specific method of discharge treatment in step (1) is as follows: the waste lithium-ion battery is completely immersed in a sodium sulfate electrolyte solution with a mass concentration of 5-10% and left to stand for 24 hours. The electrolyte solution establishes an ion conduction path between the inside and outside of the battery, and the residual charge is fully released. Then the battery is placed in a forced-air drying oven at 60℃±5℃ and dried for 2-3 hours to ensure that the residual charge of the battery is ≤0.01C and to avoid safety hazards during disassembly.

[0009] Preferably, the cathode-specific treatment in step (1) includes the following sub-steps: Step (11): Use mechanical dismantling equipment to disassemble waste lithium-ion batteries and separate the positive electrode, negative electrode, separator, plastic shell and metal shell in sequence. During the dismantling process, control the ambient humidity ≤60% and the temperature 20~25℃. Step (12): Cut the positive electrode sheet into regular small pieces of 10mm×20mm±1mm, put them into the cleaning tank of the ultrasonic cleaner, add deionized water until the electrode sheet is completely submerged, set the cleaning temperature to 70℃±3℃, ultrasonic power to 240W±10W, ultrasonic frequency to 40~60kHz, and continue the treatment for 90min±5min to completely peel the aluminum foil from the positive electrode active material, with a peeling rate ≥99%; Step (13): Place the obtained positive electrode material into a muffle furnace and heat it to 700℃±20℃ at a heating rate of 5℃ / min. Calcinate it at a constant temperature for 120min±10min to completely remove graphite and residual organic binder. The carbon content of the material after calcination is ≤1.0%. The positive electrode material includes a mixture of positive electrode active material and graphite. Step (14): Transfer the calcined material into a planetary ball mill, add agate balls, the ball-to-material ratio is 10:1, and ball mill at a speed of 300-400 r / min for 60 min ± 5 min to obtain lithium cobalt oxide powder cathode material with a particle size of 1-20 μm and a particle size distribution uniformity ≤2.

[0010] As a preferred option, the preparation parameters of the acetic acid solution in step (2) are as follows: acetic acid with a purity of ≥99.5% is selected as the raw material, the volume ratio of acetic acid to deionized water is 14:(14~56), wherein acetic acid is fixed at 14 ml, and the amount of deionized water added is 14~56 ml. During the preparation process, the solution is magnetically stirred at 25℃ for 15~20 min to ensure that the solution is mixed evenly. The final volume of the acetic acid solution is 28~70 ml, the concentration is 3.5~6 mol / L, and the pH value is 1.0~2.5.

[0011] Preferably, the parameters of the leaching reaction in step (3) are as follows: the solid-liquid ratio of lithium cobalt oxide powder to acetic acid solution is 3-10 g / L; the reducing agent is a 30 wt% hydrogen peroxide solution, added at a rate of 5-10 vol%; mechanical stirring is used at a speed of 400-700 r / min; the temperature fluctuation is controlled to ≤±2℃ during the reaction using a constant temperature water bath; after the reaction, the solution is filtered through a 0.22 μm organic filter membrane, and the filtrate is collected as the leachate, wherein the cobalt leaching rate is ≥92%, and the Co content in the leachate is ≥92%. 2+ The concentration is 0.5–6.0 g / L.

[0012] As a preferred option, the preferred parameters for the leaching reaction in step (3) are: solid-liquid ratio of 3 to 10 g / L, hydrogen peroxide addition of 5 to 10 vol%, reaction temperature of 70℃ ± 2℃, stirring speed of 500 r / min ± 30 r / min, and reaction time of 60 min ± 5 min. It can be used for subsequent MOF synthesis without additional purification.

[0013] Preferably, the preparation parameters of the mixed solution in step (4) are as follows: the volume of the leachate is 20-70 ml, the purity of the organic ligand triphenyl benzoic acid is ≥99%, the added mass is 0.2-0.6 g, the heating temperature is controlled at 40-60℃±2℃, magnetic stirring is used, the stirring speed is 300-600 r / min, the heating and stirring time is 20-40 min, and the dissolution status is observed every 10 min to ensure that the triphenyl benzoic acid is completely dissolved. The resulting mixed solution is uniform and transparent, without precipitation or stratification, and the pH value is 1.0-2.4.

[0014] As a preferred option, the preferred preparation parameters for the mixed solution in step (4) are as follows: 20-70 ml of leachate, 0.5 g of trimesic acid, heating temperature of 60℃±2℃, stirring speed of 400 r / min±30 r / min, heating and stirring time of 30 min, standing for 10-15 min after stirring to remove any small bubbles that may exist in the solution, the uniformity error of the concentration of the resulting mixed solution is ≤±2%, and the molar ratio of ligand to metal ion is 1:(0.5-7.0).

[0015] As a preferred embodiment, the parameters of the hydrothermal reaction in step (5) are as follows: the volume of the polytetrafluoroethylene liner of the hydrothermal reactor is 50-200 ml, the amount of mixed solution added does not exceed 80% of the liner volume, after sealing, it is placed in a programmed temperature-increasing oven with a heating rate of 10℃ / min, a reaction temperature of 120-135℃±5℃, and a reaction time of 12-48h±1h; among which, the preferred reaction conditions are 130℃±2℃ and 6h±0.5h. Under these conditions, the Co3(BTC)2·12H2O prepared has high crystallinity, and the 2θ in the XRD pattern shows characteristic diffraction peaks at 17.5°, 18.7°, 27.1°, and 28.6°, with a peak position deviation from the standard pattern ≤±0.2° and no obvious interference from impurity peaks.

[0016] Preferably, the washing process in step (6) is as follows: the solid product is washed 3 to 5 times with deionized water with a resistivity ≥18.2MΩ·cm using a combination of soaking and stirring. The amount of deionized water added each time is 5 to 10 times the mass of the solid product. After soaking for 5 to 10 minutes, the product is stirred for 1 to 2 minutes and then filtered through a 0.22μm filter membrane. The conductivity of the final washing solution is ≤10μS / cm. The drying process is as follows: the washed solid product is placed in a drying oven and dried for 8 to 12 hours at a temperature of 60 to 80℃±3℃. After drying, the three-dimensional porous crystal structure of the product Co3(BTC)2·12H2O is intact and there is no lattice distortion.

[0017] Compared with the prior art, the beneficial effects of the present invention are: I. Achieving efficient resource recycling and coordinated environmental protection This invention innovatively uses leachate from spent lithium-ion batteries as the core raw material for MOF material synthesis, successfully achieving the high-value conversion of cobalt resources from spent batteries. Cobalt and other valuable metals contained in spent lithium-ion batteries are scarce strategic resources. Traditional disposal methods, such as landfilling or incineration, not only cause serious resource waste but may also lead to the leakage of heavy metals and toxic electrolytes, polluting soil and water bodies. This invention extracts cobalt from spent batteries through a scientific leaching process, converting it into metal nodes for synthesizing MOF materials. This allows for the full utilization of urban mineral resources while reducing the environmental damage caused by spent batteries at the source, aligning with the global consensus on green and sustainable development and achieving the dual goals of resource recycling and environmental protection.

[0018] II. The process design is scientific, reasonable, and highly practical. The synthesis process of this invention has significant advantages such as mild conditions, high controllability, and simple operation. From raw material preparation and solution configuration to hydrothermal reaction, washing, and drying, the parameters for each step are clearly defined and easily controlled, requiring no complex equipment or harsh reaction environment. The leaching process uses acetic acid solution with an appropriate amount of hydrogen peroxide as a reducing agent, achieving efficient leaching of cobalt at a mild temperature, avoiding the use of highly corrosive reagents and reducing process difficulty and safety risks. In the hydrothermal reaction stage, optimized temperature and time parameters ensure the targeted synthesis of the target product. The entire process is seamless and highly efficient, suitable for small-scale laboratory preparation and possessing the potential for large-scale industrial applications, significantly reducing the preparation cost and barriers to the promotion of MOF materials.

[0019] III. The target product has high purity and excellent and stable performance. This invention successfully prepared high-purity Co3(BTC)2·12H2O metal-organic framework (MOF) materials by precisely controlling the process parameters at each stage. The XRD pattern of the product showed high agreement with the standard pattern, with clear characteristic diffraction peaks and no obvious impurities, proving its high crystallinity and regular structure. This MOF material inherits the inherent advantages of metal-organic framework materials, laying a solid foundation for its application in adsorption separation, catalytic reactions, gas storage, and other fields. Meanwhile, the strict limitation of process parameters ensured the stability and consistency of product performance, avoiding structural defects or performance degradation caused by fluctuations in reaction conditions, thus improving the reliability and application value of the product.

[0020] IV. Expanding Industrial Application Paths and Facilitating Industrial Upgrading This invention bridges the gap between the waste lithium-ion battery recycling and MOF material preparation industries, providing a new path for the coordinated development of related industries. On the one hand, it offers high-value end-product options for the resource-based recycling of waste lithium-ion batteries, breaking through the traditional single-mode recycling approach limited to metal element refining, and enhancing the economic benefits and market competitiveness of the waste battery recycling industry. On the other hand, it provides a low-cost, environmentally friendly source of raw materials for MOF material synthesis, eliminating dependence on pure metal salt precursors and enriching the preparation strategies for MOF materials. This invention not only promotes the deep integration of the new energy waste recycling industry and the new materials industry, but also provides high-performance new materials for multiple fields such as environmental protection, chemical engineering, and energy, possessing broad application prospects and significant industrial value. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are explained in detail together with the embodiments of the invention, but do not constitute a limitation thereof.

[0022] Figure 1 XRD pattern of Co3(BTC)2·12H2O metal-organic framework material; Figure 2 XRD patterns of hydrothermal products under conditions of 130℃ and 6h. Figure 3 XRD patterns of hydrothermal products under conditions of 130℃ and 24h; Figure 4 The XRD patterns of the hydrothermal products under conditions of 105℃ and 48h are shown. Figure 5 The XRD patterns of the hydrothermal products under conditions of 130℃ and 48h are shown. Figure 6 The XRD patterns of the hydrothermal products under conditions of 140℃ and 30h are shown. Figure 7 This is a flowchart illustrating the process of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 1. Raw material preparation Waste lithium cobalt oxide batteries were completely immersed in an 8% sodium sulfate electrolyte solution and left to stand for 24 hours to release residual charge. They were then dried in a 60℃ forced-air drying oven for 2.5 hours to ensure residual charge ≤0.01C. The batteries were disassembled using mechanical disassembly equipment in an environment of 22℃ and 55% humidity, separating the positive electrode, negative electrode, separator, plastic casing, and metal casing. The positive electrode was cut into regular 10mm×20mm pieces and placed in an ultrasonic cleaner. Deionized water was added to completely submerge the electrode. The cleaning temperature was set to 70℃, ultrasonic power to 240W, and ultrasonic frequency to 50kHz, and the treatment was continued for 90 minutes, achieving a 99.5% peeling rate between the aluminum foil and the positive electrode active material. The peeled positive electrode material (a mixture of positive electrode active material and graphite) was placed in a muffle furnace and heated to 700℃ at a rate of 5℃ / min, then calcined at this temperature for 120 minutes. The carbon content of the calcined material was 0.3%. The calcined material was transferred to a planetary ball mill, and agate balls (ball-to-material ratio 10:1) were added. The mill was then ball-milled for 60 minutes at a speed of 350 r / min to obtain lithium cobalt oxide (LiCoO2) powder cathode material with a particle size of 2-5 μm and a particle size distribution uniformity of 1.5.

[0025] 2. Solution preparation Acetic acid with a purity of 99.8% was selected as the raw material. 14 ml of acetic acid was placed in a beaker, and 56 ml of deionized water was added. The mixture was magnetically stirred at 25°C for 18 min. After mixing evenly, 70 ml of acetic acid solution with a concentration of 3.5 mol / L and a pH value of 2.1 was obtained.

[0026] 3. Leaching reaction Lithium cobalt oxide powder was mixed with the above acetic acid solution at a solid-liquid ratio of 8 g / L. A 3 vol% (w / v) 30 wt% hydrogen peroxide solution was added as a reducing agent. The mixture was placed in a constant-temperature water bath, and the reaction temperature was controlled at 70℃, the stirring speed at 500 r / min, and the reaction was carried out for 60 min. After the reaction, the mixture was filtered through a 0.22 μm organic filter membrane, and the filtrate was collected as the leachate. The cobalt leaching rate was >95%, and the Co content in the leachate was [missing information]. 2+ The concentration is 1.8 g / L.

[0027] 4. Preparation of mixed solutions Measure 50 ml of the above leachate into a beaker, add 0.5 g of 99.2% pure pyromellitic acid solid powder, set the heating temperature to 60℃ and the magnetic stirring speed to 400 r / min, heat and stir for 30 min, observing the dissolution status every 10 min during this period, until the pyromellitic acid is completely dissolved. After stirring, let stand for 12 min to remove tiny air bubbles. The resulting mixed solution is uniform and transparent, without precipitation or stratification, with a pH of 3.5, a concentration uniformity error of ±1.2%, and a ligand to metal ion molar ratio of 1:3.

[0028] 5. Hydrothermal reaction The mixed solution was transferred to a 100 ml PTFE-lined hydrothermal reactor, with the solution volume being 50% (50 ml) of the liner volume. After sealing and assembly, the reactor was placed in a programmed temperature oven and heated to 130 °C at a rate of 10 °C / min, maintaining the reaction temperature for 6 hours. After the reaction was completed, the hydrothermal reactor was allowed to cool naturally to room temperature.

[0029] 6. Wash and dry The solid product after the hydrothermal reaction was collected by filtration and then soaked and washed four times with deionized water (resistivity 18.25 MΩ·cm) with stirring. Each time, the amount of deionized water added was 8 times the mass of the solid product. After soaking for 8 minutes, the mixture was stirred for 1.5 minutes and then filtered through a 0.22 μm filter membrane. The washed solid product was then placed in a drying oven and dried at 70℃ for 10 hours.

[0030] 7. Product Characterization Finally, the metal-organic framework material Co3(BTC)2·12H2O was obtained. XRD analysis showed that its spectrum was consistent with... Figure 1 The standard spectra shown are completely consistent. The characteristic diffraction peaks of 2θ at 17.5°, 18.7°, 27.1°, and 28.6° have a peak position deviation of ≤ ±0.1°, with no impurity peaks or lattice distortion.

[0031] Example 2 1. Raw material preparation Waste lithium cobalt oxide batteries were immersed in a 6% sodium sulfate solution and left to stand for 24 hours, then dried at 60°C for 2 hours, resulting in a residual charge ≤0.01C. The batteries were disassembled at 23°C and 58% humidity. After separating the positive electrode sheet, the pieces were cut into 9mm × 21mm (±1mm error) pieces and placed in an ultrasonic cleaner. The cleaning temperature was set to 68°C, ultrasonic power to 235W, and ultrasonic frequency to 45kHz, and the treatment time was 88 minutes, achieving an aluminum foil peeling rate of 99.2%. The positive electrode material was heated to 690°C in a muffle furnace at a rate of 5°C / min and calcined at this temperature for 115 minutes, resulting in a carbon content of 0.4%. Ball milling was performed at a rotation speed of 320 r / min for 58 minutes to obtain lithium cobalt oxide powder with a particle size of 3–4 μm and a particle size distribution uniformity of 1.1.

[0032] 2. Solution preparation Measure 14 ml of acetic acid with a purity of 99.5%, add 42 ml of deionized water, stir magnetically at 25°C for 16 min, and prepare a 56 ml acetic acid solution with a concentration of 4 mol / L and a pH of 1.7.

[0033] 3. Leaching reaction Lithium cobalt oxide powder was mixed with acetic acid solution at a solid-liquid ratio of 6 g / L, and 7 vol% of 30 wt% hydrogen peroxide solution was added. The mixture was reacted in a constant temperature water bath at 65℃ and a stirring speed of 550 r / min for 70 min. After filtration, the cobalt leaching rate in the leachate was 93%. 2+ Concentration 2.5 g / L.

[0034] 4. Preparation of mixed solutions Take 40 ml of leachate, add 0.4 g of 99% pure triphenyl benzoic acid, heat to 55℃, stir at 450 r / min for 35 min, and let stand for 10 min to obtain a uniform and transparent solution with pH 3.3, concentration uniformity error ±1.5%, and ligand to metal ion molar ratio of 1:1.7.

[0035] 5. Hydrothermal reaction A 100ml hydrothermal reactor was used. The amount of mixed solution added was 40% of the liner volume. After sealing, the temperature was increased to 130℃ at 10℃ / min and reacted for 6 hours. The mixture was then allowed to cool naturally to room temperature.

[0036] 6. Wash and dry The solid was washed three times with 18.21 MΩ·cm deionized water, with each wash using 7 times the mass of the solid. The washings were soaked for 6 min and stirred for 1 min. The conductivity of the final wash solution was 9 μS / cm. The solid was dried at 65℃ for 9 h, yielding the product Co3(BTC)2·12H2O.

[0037] Example 3 1. Raw material preparation Waste batteries were immersed in a 5% sodium sulfate solution and left to stand for 24 hours, then dried at 60℃ for 3 hours, with a residual charge ≤0.01C. Disassembly was carried out at 20℃ and 50% humidity. The positive electrode sheet was cut into 11mm×19mm (error ±1mm) pieces. Ultrasonic cleaning parameters were: temperature 73℃, power 245W, frequency 55kHz, and processing time 92min, achieving an aluminum foil peeling rate of 99.1%. The positive electrode material was heated to 720℃ in a muffle furnace (heating rate 5℃ / min) and calcined at a constant temperature for 125min, resulting in a carbon content of 0.5%. Ball milling at 380r / min for 62min yielded lithium cobalt oxide powder with a particle size of 4–5μm and a particle size distribution uniformity of 1.2.

[0038] 2. Solution preparation Add 14 ml of acetic acid (99.5% purity) to 14 ml of deionized water, stir at 25°C for 20 min to prepare 28 ml of acetic acid solution with a concentration of 6 mol / L and a pH of 0.6.

[0039] 3. Leaching reaction Lithium cobalt oxide powder (solid-liquid ratio 10 g / L) was mixed with acetic acid solution, and 10 vol% of 30 wt% hydrogen peroxide was added. The reaction was carried out at 75℃ and 600 r / min for 80 min. After filtration, the cobalt leaching rate of the leachate was 92%. 2+ Concentration 4.2 g / L.

[0040] 4. Preparation of mixed solutions Take 20 ml of leachate, add 0.2 g of trimesic acid (purity 99%), heat to 45℃, stir at 350 r / min, heat and stir for 25 min, let stand for 15 min to obtain a homogeneous solution with pH 3.7, concentration uniformity error ±1.8%, and ligand to metal ion molar ratio 1:1.2.

[0041] 5. Hydrothermal reaction A 50ml hydrothermal reactor was used. The amount of mixed solution added was 40% of the liner volume. The heating rate was 10℃ / min. The temperature was raised to 130℃ and reacted for 6 hours. The mixture was then allowed to cool naturally to room temperature.

[0042] 6. Wash and dry The solid was washed five times with deionized water, each time using 10 times the mass of the solid. The washings were soaked for 10 minutes and stirred for 2 minutes. The conductivity of the final wash solution was 7 μS / cm. The drying conditions were 75℃ for 11 hours, yielding the product Co3(BTC)2·12H2O.

[0043] IV. Comparative Examples (Deviating from Key Hydrothermal Parameters) 1. Raw material preparation Completely consistent with Example 1, lithium cobalt oxide powder cathode material of the same specifications was obtained.

[0044] 2. Solution preparation The same as in Example 1 was used to prepare a 3.5 mol / L acetic acid solution.

[0045] 3. Leaching reaction Completely consistent with Example 1, a cobalt acetate leaching solution of the same purity was obtained.

[0046] 4. Preparation of mixed solutions Completely consistent with Example 1, a homogeneous mixed solution was obtained.

[0047] 5. Hydrothermal reaction The mixed solution was transferred to a hydrothermal reactor of the same specifications, sealed, and heated at 10℃ / min to the conditions in Table 1 for reaction. After the reaction was completed, it was allowed to cool naturally to room temperature.

[0048] Table 1 6. Wash and dry The washing and drying process is exactly the same as in Example 1.

[0049] 7. Product Characterization XRD analysis showed that the product chromatogram was similar to... Figure 1 The standard spectrum of Co3(BTC)2·12H2O shown is significantly different, lacking the characteristic diffraction peaks at 17.5°, 18.7°, 27.1°, and 28.6°. The spectrum corresponds to... Figures 3-6 It is not the target product; it has low crystallinity and no obvious porous structure, and cannot meet the performance requirements of the target MOF material.

[0050] Comparison Conclusion The comparative example showed that the hydrothermal reaction temperature (105℃ or 140℃) was lower than the core range of the preferred range of 120-135℃ defined in the claims of this invention, and the reaction time (24h-48h) deviated from the optimal reaction time. As a result, the metal ions and organic ligands could not coordinate and assemble according to the target ratio and structure, and Co3(BTC)2·12H2O was ultimately not prepared. This proves that the key parameters such as hydrothermal reaction temperature and time defined in this invention are necessary conditions for achieving the synthesis of the target product.

[0051] The data from the above three sets of examples and the comparative examples at 105℃ and 48h are compared in Table 2 below.

[0052] Table 2 The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries, characterized in that, Includes the following steps: (1) Raw material preparation: After the waste lithium-ion batteries are discharged, disassembled and separated, and the cathode is specially treated, high-purity lithium cobalt oxide LiCoO2 powder cathode material is obtained; (2) Solution preparation: Measure the acetic acid reagent, add deionized water and stir evenly to prepare an acetic acid solution with a concentration of 2-6 mol / L; (3) Leaching reaction: The lithium cobalt oxide powder obtained in step (1) is mixed with the acetic acid solution prepared in step (2) in proportion, and hydrogen peroxide H2O2 is added as a reducing agent. The mixture is heated and stirred at 50-80℃ for 40-90 min. After the reaction is completed, the mixture is filtered and the leachate containing cobalt acetate Co(Ac)2 is collected. (4) Preparation of mixed solution: Add organic ligand pyromellitic acid solid powder to the leachate obtained in step (3), heat and stir at 40-60°C to completely dissolve pyromellitic acid and obtain a uniform mixed solution; (5) Hydrothermal reaction: The mixed solution obtained in step (4) is transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and subjected to a hydrothermal reaction at 120-135°C for 12-48 hours. After the reaction is completed, the hydrothermal reactor is naturally cooled to room temperature. (6) Washing and drying: The solid product after hydrothermal reaction is filtered and separated, washed and dried to finally obtain the metal-organic framework material Co3(BTC)2·12H2O.

2. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The specific method of discharge treatment in step (1) is as follows: the waste lithium-ion battery is completely immersed in a sodium sulfate electrolyte solution with a mass concentration of 5-10% and left to stand for 24 hours. The electrolyte solution establishes an ion conduction path between the inside and outside of the battery, and the residual charge is fully released. Then the battery is placed in a forced-air drying oven at 60℃±5℃ and dried for 2-3 hours to ensure that the residual charge of the battery is ≤0.01C and to avoid safety hazards during disassembly.

3. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The cathode-specific treatment described in step (1) includes the following sub-steps: Step (11): Use mechanical dismantling equipment to disassemble waste lithium-ion batteries and separate the positive electrode, negative electrode, separator, plastic shell and metal shell in sequence. During the dismantling process, control the ambient humidity ≤60% and the temperature 20~25℃. Step (12): Cut the positive electrode sheet into regular small pieces of 10mm×20mm±1mm, put them into the cleaning tank of the ultrasonic cleaner, add deionized water until the electrode sheet is completely submerged, set the cleaning temperature to 70℃±3℃, ultrasonic power to 240W±10W, ultrasonic frequency to 40~60kHz, and continue the treatment for 90min±5min to completely peel the aluminum foil from the positive electrode active material, with a peeling rate ≥99%; Step (13): Place the obtained positive electrode material into a muffle furnace and heat it to 700℃±20℃ at a heating rate of 5℃ / min. Calcinate it at a constant temperature for 120min±10min to completely remove graphite and residual organic binder. The carbon content of the material after calcination is ≤1.0%. The positive electrode material includes a mixture of positive electrode active material and graphite. Step (14): Transfer the calcined material into a planetary ball mill, add agate balls, the ball-to-material ratio is 10:1, and ball mill at a speed of 300-400 r / min for 60 min ± 5 min to obtain lithium cobalt oxide powder cathode material with a particle size of 1-20 μm and a particle size distribution uniformity ≤2.

4. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The preparation parameters of the acetic acid solution in step (2) are as follows: acetic acid with a purity of ≥99.5% is selected as the raw material, the volume ratio of acetic acid to deionized water is 14:(14~56), wherein acetic acid is fixed at 14ml, and the amount of deionized water added is 14~56ml. During the preparation process, the solution is magnetically stirred at 25℃ for 15~20min to ensure that the solution is mixed evenly. The final solution volume is 28~70ml, the concentration is 3.5~6mol / L, and the pH value is 1.0~2.

5.

5. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The parameters for the leaching reaction in step (3) are as follows: the solid-liquid ratio of lithium cobalt oxide powder to acetic acid solution is 3-10 g / L; the reducing agent is a 30 wt% hydrogen peroxide solution, added at a rate of 5-10 vol%; mechanical stirring is used at a speed of 400-700 r / min; the temperature fluctuation is controlled to ≤±2℃ during the reaction using a constant temperature water bath; after the reaction, the solution is filtered through a 0.22 μm organic filter membrane, and the leachate is collected, wherein the cobalt leaching rate is ≥92%, and the Co content in the leachate is ≥92%. 2+ The concentration is 0.5–6.0 g / L.

6. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, In step (3), the solid-liquid ratio in the leaching reaction is 3-10 g / L, the amount of hydrogen peroxide added is 5-10 vol%, the reaction temperature is 70℃±2℃, the stirring speed is 500 r / min±30 r / min, and the reaction time is 60 min±5 min. At this time, the leaching solution contains cobalt acetate and can be used for subsequent MOF synthesis without additional purification.

7. The method for hydrothermal synthesis of metal-organic frameworks from spent lithium-ion batteries according to claim 1, characterized in that, The preparation parameters of the mixed solution in step (4) are as follows: the volume of the leachate is 20-70 ml, the purity of the organic ligand pyromellitic acid is ≥99%, the added mass is 0.2-0.6 g, the heating temperature is controlled at 40-60℃±2℃, the magnetic stirring method is used, the stirring speed is 300-600 r / min, the heating and stirring time is 20-40 min, and the dissolution status is observed every 10 min to ensure that the pyromellitic acid is completely dissolved. The resulting mixed solution is uniform and transparent, without precipitation or stratification, and the pH value is 1.0-2.

4.

8. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The preferred preparation parameters for the mixed solution in step (4) are as follows: 20-70 ml of leachate, 0.5 g of trimesic acid, heating temperature 60℃±2℃, stirring speed 400 r / min±30 r / min, heating and stirring time 30 min, and standing for 10-15 min after stirring to remove any small bubbles that may exist in the solution. The uniformity error of the concentration of the resulting mixed solution is ≤±2%, and the molar ratio of ligand to metal ion is 1:(0.5-7.0).

9. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The parameters of the hydrothermal reaction in step (5) are as follows: the volume of the polytetrafluoroethylene liner of the hydrothermal reactor is 50-200 ml, the amount of mixed solution added does not exceed 80% of the liner volume, after sealing, it is placed in a programmed temperature oven with a heating rate of 10℃ / min, a reaction temperature of 120-135℃±5℃, and a reaction time of 12-48h±1h.

10. The method for hydrothermal synthesis of metal-organic frameworks using leachate from spent lithium-ion batteries according to claim 1, characterized in that, The washing process in step (6) is as follows: the solid product is washed 3 to 5 times with deionized water with a resistivity ≥18.2MΩ·cm using a combination of soaking and stirring. The amount of deionized water added each time is 5 to 10 times the mass of the solid product. After soaking for 5 to 10 minutes, the product is stirred for 1 to 2 minutes and then filtered through a 0.22μm filter membrane. The conductivity of the final washing solution is ≤10μS / cm. The drying process is as follows: the washed solid product is placed in a drying oven and dried for 8 to 12 hours at a temperature of 60 to 80℃±3℃ to maintain the integrity of the three-dimensional porous crystal structure of Co3(BTC)2·12H2O without lattice distortion.

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