A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using deep eutectic solvents

Abstract

A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, which relates to a method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries. The present invention aims to solve the technical problems of high cost, easy generation of intermediate pollution, and difficulty in selectively separating transition metals in the existing methods for leaching transition metals from the cathode material of waste ternary lithium batteries. The present invention includes two steps: preparing a deep eutectic solvent and selectively leaching ternary powder. The deep eutectic solvent provided by the present invention has good thermal stability, and at the same time has a good selective leaching effect on lithium, cobalt, and manganese in the cathode powder of waste ternary lithium batteries, and hardly leaches nickel under certain conditions. By adjusting the leaching conditions, the present invention for the first time selectively leaches and separates transition metals nickel and cobalt with similar chemical properties in the cathode powder at the leaching stage under mild conditions and in a short time.

Description

Technical Field

[0001] The present invention relates to a method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries. Background Art

[0002] With the growing energy demand, it is met by rechargeable lithium-ion batteries. However, the accelerated production of these devices will soon translate into a large amount of waste. Since the lifespan of lithium-ion batteries in small electronic products is only about 3 years, and that of electric vehicles is only 5 - 10 years, a large amount of lithium-ion waste will be generated in the future. The development of sustainable recycling methods for lithium-ion batteries can minimize adverse effects and alleviate the constraints on the supply chain of battery manufacturers. For example, metals such as lithium, nickel, and cobalt in the cathode material of lithium-ion batteries are global strategic resources and are expensive, with high recycling value. It is predicted that the future demand for key elements (especially cobalt and nickel) will exceed the identified reserves, and the geographical and environmental pressures associated with major mining operations will continue to increase. Therefore, there is an urgent need to develop sustainable recycling methods to recover key elements from potential valuable secondary resources. However, due to the complex composition of lithium-ion batteries and the similar physical and chemical properties of metals nickel and cobalt, it is difficult to selectively separate them in the leached solution. Currently, domestic and foreign leaching methods usually adopt wet leaching, using inorganic or organic acids to uniformly acid-leach ternary powders, and then extraction and separation process methods, which often rely on solvent extraction. This method usually exhibits high selectivity performance, but it will not only have an adverse impact on the environment, but also incur high chemical costs or waste, and may face challenges in the complex chemical morphology of the solution. Therefore, compared with the above methods, a method that uses a relatively environmentally friendly solvent and can achieve selective leaching of nickel and cobalt at the leaching stage undoubtedly has a very broad application prospect.

[0003] Deep eutectic solvents are a new type of green reagent that can replace ionic liquids. They are eutectic mixtures composed of a hydrogen bond donor and a hydrogen bond acceptor with relatively high original melting points. Due to the charge delocalization caused by hydrogen bonding between the two, deep eutectic solvents contain large, asymmetric ions and have low lattice energy. Therefore, they have a low melting point, and the reduced melting point makes them liquid at room temperature. Summary of the Invention

[0004] The present invention aims to solve the technical problems of the existing leaching methods for transition metals in the cathode material of ternary lithium batteries, such as high cost, easy generation of intermediate pollution, and difficulty in selectively separating transition metals, and provides a method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using deep eutectic solvents.

[0005] The method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using deep eutectic solvents of the present invention is carried out according to the following steps:

[0006] 1. Add a hydrogen bond acceptor, a hydrogen bond donor, and a diluent into a round-bottom flask, and heat and stir until a homogeneous, clear, and deep eutectic solvent is obtained.

[0007] The hydrogen bond acceptor, hydrogen bond donor, and diluent are choline chloride, malonic acid, and deionized water in sequence.

[0008] 2. Add the deep eutectic solvent obtained in step 1 and the waste NCM ternary lithium battery cathode material powder into a round-bottom flask, and heat and stir in an oil bath for 45 min to 60 min at a heating temperature of 80 °C to 100 °C, thus completing the selective leaching and separation of nickel and other metals in the ternary lithium battery cathode material powder.

[0009] The reason why the deep eutectic solvent prepared in step 1 of the present invention can achieve the selective leaching of nickel and other metal ions is as follows:

[0010] First, nickel and the hydrogen bond donor malonic acid can form nickel malonate dihydrate, which is an insoluble precipitate under the conditions of the present invention; choline chloride forms a more stable complex [CoCl4] with Co ions 2- , so Co will not precipitate.

[0011] Second, when transition metals form five-membered ring chelate complexes with malonic acid, the stability of nickel complexes is greater than that of cobalt complexes.

[0012] Third, the protons contained in malonic acid act as oxygen acceptors, which not only enable the efficient leaching of metallic lithium but also change the complex formed with chloride ions. The present invention designs this deep eutectic solvent based on this.

[0013] Using the leaching method of the present invention and applying it to the sustainable recycling of waste NCM ternary lithium battery cathode materials, it has good selective leaching performance for nickel and other metal ions, solves the technical problems such as long process flow, high chemical costs (extractants and energy), and environmental pollution existing in the current process, and provides a feasible path for the sustainable recycling of current NCM ternary cathode materials.

[0014] Because the properties of nickel and cobalt are very similar, it is very difficult to achieve the selectivity of nickel and cobalt in the leaching stage. The leaching method of the present invention only leaches cobalt but does not leach nickel, and under this condition, nickel will form insoluble complexes.

[0015] The deep eutectic solvent synthesis method of the present invention is simple, low-cost, and environmentally friendly, and has great potential for industrial applications. The method provided by the present invention can selectively leach and separate nickel and other metal ions, and has the characteristics of high leaching efficiency: lithium, cobalt, and manganese are almost 100% leached; good selectivity: almost no leaching of nickel; low cost and being a green solvent. Description of the Drawings

[0016] Figure 1 It is the data graph of the leaching and separation effect in Experiment 1;

[0017] Figure 2 It is Figure 1 the data graph at 100 °C in

[0018] Figure 3 It is the XRD characterization graph of the raw material NCM811 and the residue after leaching at different temperatures in Experiment 1;

[0019] Figure 4 It is the data graph of the leaching and separation effect in Experiment 2;

[0020] Figure 5 It is the data graph of the leaching and separation effect in Experiment 3;

[0021] Figure 6 It is the data graph of the leaching and separation effect in Experiment 4. Detailed Description of the Invention

[0022] Detailed Description of the Invention 1: This embodiment is a method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, and the specific steps are as follows:

[0023] 1. Add a hydrogen bond acceptor, a hydrogen bond donor, and a diluent to a round-bottom flask, and heat and stir until a uniform and clear deep eutectic solvent is obtained;

[0024] The hydrogen bond acceptor, hydrogen bond donor, and diluent are choline chloride, malonic acid, and deionized water in sequence;

[0025] 2. Add the deep eutectic solvent obtained in step 1 and the powder of the cathode material of waste NCM ternary lithium batteries to a round-bottom flask, and heat and stir in an oil bath for 45 min to 60 min, and the heating temperature is 80 °C to 100 °C, then the selective leaching and separation of nickel and other metals in the powder of the cathode material of ternary lithium batteries is completed.

[0026] Detailed Description of the Invention 2: The difference between this embodiment and Detailed Description of the Invention 1 is that: the heating and stirring temperature in step 1 is 60 °C to 70 °C. Others are the same as Detailed Description of the Invention 1.

[0027] Detailed Description of the Invention 3: The difference between this embodiment and Detailed Description of the Invention 1 or 2 is that: the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor in step 1 is 1:(0.5 - 2). Others are the same as Detailed Description of the Invention 1 or 2.

[0028] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is that: the mass concentration of the diluent in the deep eutectic solvent described in Step 1 is 30% to 35%. Others are the same as any one of Embodiments 1 to 3.

[0029] Embodiment 5: The difference between this embodiment and Embodiment 4 is that: the dosage of the NCM ternary lithium battery cathode material powder in the deep eutectic solvent in Step 2 is 20 g / L to 50 g / L. Others are the same as Embodiment 4.

[0030] The present invention is verified by the following experiments:

[0031] Experiment 1: This experiment is used to illustrate the effect of temperature on a method for selectively leaching and separating transition metals from waste ternary lithium battery cathode materials using a deep eutectic solvent. Specifically, it is carried out according to the following steps:

[0032] I. Add a hydrogen bond acceptor, a hydrogen bond donor, and a diluent into a 50 mL round-bottom flask, heat and stir at 60 °C for 90 min to obtain a uniform and clear deep eutectic solvent;

[0033] The hydrogen bond acceptor, hydrogen bond donor, and diluent are choline chloride, malonic acid, and deionized water in sequence;

[0034] The molar ratio of choline chloride to malonic acid is 1:1;

[0035] The mass concentration of the diluent in the deep eutectic solvent is 35%;

[0036] II. Add the deep eutectic solvent obtained in Step I and waste nickel-cobalt-manganese ternary powder NCM811 into a round-bottom flask. The dosage of the nickel-cobalt-manganese ternary powder NCM811 is 20 g / L. Heat and stir in an oil bath at 40 °C, 60 °C, 80 °C, 100 °C, 120 °C, and 140 °C for 60 min, with a rotation speed of 400 r / min; after filtration, obtain the leaching solution, and use an atomic absorption spectrometer to measure the concentration of each metal ion in the leaching solution as Figure 1 shown, Figure 2 is Figure 1 the data graph at 100 °C in. The results show that at 100 °C, this deep eutectic solvent shows selectivity for nickel and lithium cobalt manganese, and lithium, manganese, and cobalt are almost 100% leached, while nickel is hardly leached.

[0037] The raw material NCM811 and the residues after leaching at different temperatures were characterized by X-ray diffraction (XRD), as Figure 3The XRD patterns of the raw material NCM811 at 40 °C, 80 °C, and 100 °C are shown. PDF87-1562 is the standard card of lithium nickel cobalt oxide, and PDF24-1804 is the standard card of nickel malonate dihydrate. The results show that the phase composition of the characteristic peaks of the leaching residue before 80 °C is mainly oxides of lithium, nickel, cobalt, and manganese. After leaching at 80 °C and 100 °C with the deep eutectic solvent, the phase composition of the characteristic peaks of the solid residue is nickel malonate dihydrate, indicating that the main form of nickel after 80 °C is insoluble nickel malonate dihydrate.

[0038] Experiment 2: This experiment is used to illustrate the effect of time on the method of selectively leaching metal ions from the cathode powder of waste ternary lithium batteries using a deep eutectic solvent. The specific steps are as follows:

[0039] I. Choline chloride and malonic acid were added to a 50 mL round-bottom flask in a molar ratio of 1:2, and 30 wt% deionized water was added as a diluent. The mixture was heated and stirred at 70 °C for 120 min to obtain a homogeneous and clear deep eutectic solvent.

[0040] II. The obtained deep eutectic solvent and the waste nickel cobalt manganese ternary powder NCM811 were added to a round-bottom flask at a dosage of 20 g / L. The mixture was heated and stirred in an oil bath at 100 °C for 15 min, 30 min, 45 min, 60 min, and 75 min, respectively, with a rotation speed of 400 r / min. After filtration, the leaching solution was obtained, and the concentrations of various metal ions in the leaching solution were measured using an atomic absorption spectrometer. As Figure 4 , the results show that the deep eutectic solvent exhibits the best selectivity for nickel and lithium cobalt manganese at 45 min (the leaching rate of nickel is very low, 0.78% at 100 °C and 45 min, 0.6% at 60 min, and 0.25% at 75 min).

[0041] Experiment 3: This experiment is used to illustrate the effect of the solid-liquid ratio dosage on the method of selectively leaching metal ions from the cathode powder of waste ternary lithium batteries using a deep eutectic solvent. The specific steps are as follows:

[0042] I. Choline chloride and malonic acid were added to a 50 mL round-bottom flask in a molar ratio of 2:1, and 35 wt% deionized water was added as a diluent. The mixture was heated and stirred at 60 °C for 120 min to obtain a homogeneous and clear deep eutectic solvent.

[0043] II. The obtained deep eutectic solvent and the waste nickel-cobalt-manganese ternary powder NCM811 were added to a round-bottom flask at dosages of 200 g / L, 100 g / L, 50 g / L, 30 g / L, 20 g / L, and 15 g / L respectively, heated and stirred in an oil bath at a temperature of 100 °C for 60 min at a rotation speed of 400 r / min. After filtration, the leaching solution was obtained, and an atomic absorption spectrometer was used to measure the concentrations of various metal ions in the solution. As Figure 5 The test results show that the deep eutectic solvent exhibits the best separation effect of nickel from lithium, cobalt, and manganese at 20 g / L.

[0044] Experiment 4: This experiment was used to illustrate the influence of the type of waste lithium battery on a method for selectively leaching metal ions from the cathode powder of waste ternary lithium batteries using a deep eutectic solvent. The specific steps were as follows:

[0045] I. Choline chloride and malonic acid were added to a 50 mL round-bottom flask at a molar ratio of 2:1, and 35 wt% deionized water was added as a diluent. The mixture was heated and stirred at 60 °C for 120 min to obtain a uniform and clear deep eutectic solvent;

[0046] II. The obtained deep eutectic solvent was added to a round-bottom flask at a dosage of 20 g / L respectively with the waste NCM811, waste NCM111, and waste NCM622 ternary powders. The mixture was heated and stirred in an oil bath at a temperature of 100 °C for 60 min at a rotation speed of 400 r / min. After filtration, the leaching solution was obtained, and an atomic absorption spectrometer was used to measure the concentrations of various metal ions in the solution. As Figure 6 shown, the test results show that the deep eutectic solvent has a selective effect on different types of ternary cathode materials, and this solvent exhibits the best separation effect of nickel from lithium, cobalt, and manganese for NCM811.

Claims

1. A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, characterized in that The method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent is carried out according to the following steps: First, add a hydrogen bond acceptor, a hydrogen bond donor, and a diluent into a round-bottom flask, and heat and stir until a uniform and clear deep eutectic solvent is obtained; The hydrogen bond acceptor, hydrogen bond donor, and diluent are choline chloride, malonic acid, and deionized water in sequence; Second, add the deep eutectic solvent obtained in the first step and the powder of the cathode material of the waste NCM ternary lithium battery into a round-bottom flask, and heat and stir in an oil bath for 45 min to 60 min, and the heating temperature is 80°C to 100°C, thus completing the selective leaching and separation of nickel and other metals in the powder of the cathode material of the ternary lithium battery.

2. A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, characterized in that The temperature of the heating and stirring in the first step is 60°C to 70°C.

3. A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, characterized in that The molar ratio of the hydrogen bond acceptor and the hydrogen bond donor in the first step is 1:(0.5 - 2).

4. A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, characterized in that The mass concentration of the diluent in the deep eutectic solvent in the first step is 30% - 35%.

5. A method for selectively leaching and separating transition metals from the cathode material of waste ternary lithium batteries using a deep eutectic solvent, characterized in that The dosage of the powder of the cathode material of the NCM ternary lithium battery in the deep eutectic solvent in the second step is 20 g / L to 50 g / L.

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