Method for recycling metal elements in waste ternary lithium battery

Abstract

The invention discloses a method for recycling metal elements in a waste ternary lithium battery, and relates to the technical field of waste lithium ion battery recycling. The invention relates to a method for recovering metal elements in a waste ternary lithium battery. The method comprises the following steps: S1, pretreatment: sequentially carrying out calcination and ball-milling activation treatment on a positive electrode material of a waste lithium ion battery; s2, mechanochemical leaching: carrying out ball-milling leaching on the positive electrode material activated in the step S1, oxalic acid, a reducing agent, deionized water and ball-milling beads to obtain a leaching solution; and S3, carrying out solid-liquid separation on the leachate obtained in the step S2 to obtain a lithium-rich solution and residues. According to the method, the lithium leaching efficiency is high; and even under the harsh condition of high solid-to-liquid ratio, excellent lithium leaching efficiency and selectivity can still be kept. In addition, by means of the method, residues generated in the recycling process can be utilized in a high-valued mode, and the oxygen evolution catalyst for water electrolysis is prepared.

Description

Technical Field

[0001] The present invention belongs to the field of recycling of waste lithium-ion batteries, and specifically includes a method for recycling metal elements in waste ternary lithium batteries. Background Art

[0002] With the wide application of lithium-ion batteries in the fields of new energy vehicles, energy storage, etc., their market scale has continued to grow rapidly. However, the problem of treating waste lithium-ion batteries has become increasingly prominent. Waste lithium-ion batteries not only contain various high-value metal resources such as lithium, cobalt, nickel, manganese, and copper, but also contain harmful substances such as fluorides and organic solvents. These metal resources are limited in nature, and the traditional mining and refining processes cause a greater burden on the environment; while if the harmful substances are not properly treated, they will pose a serious threat to the ecological environment and human health. Therefore, developing a green, efficient and economically viable waste lithium-ion battery recycling technology has become a key issue that needs to be solved urgently. Especially for the efficient recovery and resource utilization of lithium elements, innovative technological breakthroughs are urgently needed.

[0003] Chinese Patent CN118877949A discloses a method for recycling metal elements in waste ternary lithium batteries by mechanically chemically driven eutectic solvents, including the following steps: S1 Leaching: Ball-milling a mixture of the cathode material powder of waste ternary lithium batteries, eutectic solvents and grinding aids under the action of ball-milling media to obtain a leaching solution; S2 Precipitation: Performing fractional precipitation on the leaching solution to obtain hydroxides of Ni, Co, Mn and Li2CO3 respectively; the grinding aid is a mesoporous microsphere of (α-SiO2·H2O)x·(Al2O3)y, where x = 0.1-0.9 and y = 1-x. The eutectic solvent is at least one of choline chloride-ethylene glycol, choline chloride-urea, choline chloride-malonic acid or choline chloride-benzoic acid. When the solid-liquid ratio of the lithium battery cathode material to the eutectic solvent is 2.5 g / L, after leaching in the eutectic solvent for 120 min, the leaching efficiencies of Li, Mn, Co, and Ni can all reach more than 99%. However, this recycling method is only applicable to the case where the solid-liquid ratio of the lithium battery cathode material to the eutectic solvent is relatively low. When the solid-liquid ratio of the lithium battery cathode material to the eutectic solvent is increased to 50-100 g / L, the leaching efficiencies of Li, Mn, Co, and Ni will be significantly reduced. Summary of the Invention

[0004] The present invention aims to overcome the defects and deficiencies of the existing methods for recycling metal elements in waste ternary lithium batteries, which have low metal leaching rates under high solid-liquid ratio conditions, and provides a method for recycling metal elements in waste ternary lithium batteries, which can also maintain excellent lithium leaching efficiency under the harsh conditions of a high solid-liquid ratio between the cathode material of waste ternary lithium batteries and the extraction solution.

[0005] To achieve the above object, the present invention is implemented through the following steps:

[0006] A method for recovering metal elements from waste ternary lithium batteries, comprising the following steps:

[0007] S1. Pretreatment: successively calcining and ball-milling and activating the waste lithium-ion battery cathode material;

[0008] S2. Mechanochemical leaching: the cathode material activated in S1, oxalic acid, a reducing agent, and deionized water are ball-milled with ball-milling beads to obtain a leaching solution;

[0009] S3. Solid-liquid separation of the leaching solution obtained in step S2 to obtain a lithium-rich solution and a residue;

[0010] Among them, in step S1, the cathode material is Li(Ni x Co y Mn z )O2, where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1;

[0011] Among them, in step S2, the solid-liquid ratio of the cathode material activated in S1 to deionized water is 10-100 g / L.

[0012] Through the pretreatment step of step S1 of the present invention, after calcining the cathode material, it is beneficial to remove organic substances and pre-decompose the crystal structure, providing a porous cathode material for ball-milling. Ball-milling the calcined cathode material is beneficial to destroying its crystal structure; increasing the surface energy, thereby accelerating the solid-liquid interface reaction during acid leaching. Since cobalt and manganese in the waste lithium-ion battery cathode material are in +3 and +4 valence states respectively and are difficult to completely dissolve in acidic solutions, a reducing agent can be used to reduce cobalt and manganese to +2 valence, which is easy to leach. In step S2 of the present invention, oxalic acid is used as the leaching agent because lithium in the cathode material can be converted into water-soluble lithium oxalate, and oxalic acid can complex with other metal ions except lithium ions to form precipitates, thereby accelerating the leaching process and obtaining a lithium-rich solution with few impurity ions, high lithium leaching rate and selectivity. After solid-liquid separation in step S3, a lithium-rich solution and a residue containing nickel, cobalt, and manganese elements can be obtained.

[0013] Preferably, in step S1, the calcination temperature is 200-400 °C, and the calcination time is 20-100 min.

[0014] Preferably, in step S1, the ball-milling time is 10-100 min, the ball-milling speed is 300-600 r / min, and the mass ratio of the ball-milling beads to the cathode material is (5-25):1.

[0015] Preferably, in step S2, the mass ratio of oxalic acid to the cathode material is (0.1-3):1.

[0016] Preferably, in step S2, the reducing agent is one or more of sodium sulfite, ferrous sulfate, hydrogen peroxide, and ascorbic acid.

[0017] More preferably, the reducing agent in step S2 is hydrogen peroxide.

[0018] To avoid introducing impurity ions and affecting subsequent purification, the reducing agent is preferably hydrogen peroxide.

[0019] Preferably, in step S2, the mass ratio of the cathode material activated by S1 to the ball milling beads is 1:(10-50).

[0020] Preferably, in step S2, the temperature of the deionized water is 25-90°C.

[0021] Preferably, in step S2, the ball milling time is 3-90 min, and the rotational speed of the ball mill is 300-700 r / min.

[0022] Preferably, the solid-liquid ratio of the cathode material to the deionized water in step S2 is 10-100 g / L.

[0023] Under the harsh conditions of a high solid-liquid ratio of 50-100 g / L, the method of the present invention can still maintain excellent lithium leaching efficiency and selectivity.

[0024] The present invention also protects a method for preparing lithium carbonate, including the following steps: evaporating and crystallizing the lithium-rich solution obtained by the method for recovering metal elements from the waste ternary lithium battery described in any one of the above, and calcining to obtain Li2CO3.

[0025] The present invention also protects a method for preparing an oxygen evolution catalyst for electrolyzing water. The residue obtained by the method for recovering metal elements from the waste ternary lithium battery described in any one of the above is calcined at 200-800°C to prepare an oxygen evolution catalyst for electrolyzing water.

[0026] In the specific implementation manner, the calcination temperature can be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C.

[0027] Preferably, the calcination temperature is 450-500°C. The calcination temperature affects the performance of the oxygen evolution catalyst material. A slightly higher calcination temperature is beneficial to reducing the overpotential and Tafel slope.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The present invention provides a method for recovering metal elements from waste ternary lithium batteries. The cathode material of waste lithium-ion batteries is activated through pre-treatment of calcination and ball milling, and based on mechanochemistry, a synergistic process of ball milling and leaching is adopted to achieve efficient recovery of lithium from waste ternary lithium batteries, with excellent lithium leaching efficiency and selectivity.

[0030] Moreover, the method of the present invention can also highly utilize the residues generated during the recovery process to prepare an oxygen evolution catalyst for electrolyzing water. Description of the Drawings

[0031] Figure 1 XRD pattern obtained by comparing the X-ray diffraction peaks of Li2CO3 obtained in Example 1 with the standard card.

[0032] Figure 2 XRD patterns of the cathode material of waste lithium-ion batteries before and after pre-treatment in Example 1.

[0033] Figure 3 BET patterns of the cathode material of waste lithium-ion batteries before and after pre-treatment in Example 1.

[0034] Figure 4 Linear sweep voltammetry (LSV) curve and Tafel curve when the residue in Example 1 is used as an oxygen evolution catalyst for electrolyzing water.

[0035] Figure 5 Linear sweep voltammetry (LSV) curve and Tafel curve when the residue in Example 8 is used as an oxygen evolution catalyst for electrolyzing water. Detailed Embodiments

[0036] The present invention will be further described below in conjunction with the drawings in the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0037] Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

[0038] Example 1

[0039] A method for recovering metal elements from waste ternary lithium batteries includes the following steps:

[0040] S1. Pre-treatment: The cathode material of waste lithium-ion batteries is sequentially subjected to calcination and ball milling activation treatment.

[0041] Specifically, in a nitrogen atmosphere, 4 g of Li(Ni 0.5 Co 0.2 Mn 0.3)The O2 cathode material is heated to 300 °C at a heating rate of 5 °C / min and calcined for 60 min. After the calcination, it is allowed to cool naturally to room temperature. Subsequently, the calcined cathode material is placed in a 100 ml ball mill jar, and 60 g of ball milling beads are added so that the mass ratio of the ball milling beads to the cathode material is 15:1. Ball milling is carried out at a rotation speed of 600 r / min for 60 min to obtain the activated cathode material.

[0042] S2. Mechanochemical leaching: The activated cathode material, oxalic acid, reducing agent, and deionized water after S1 are mixed at a certain solid-liquid ratio and added to the ball mill jar. A certain mass of ball milling beads is added and ball milling leaching is carried out at a certain rotation speed to obtain the leaching solution.

[0043] Specifically, in a 100 ml ball mill jar, 40 g of ball milling beads are loaded, and 2 g of the activated cathode material after S1, 4 g of oxalic acid (the mass ratio of oxalic acid to the cathode material is 2:1), 0.5 ml of hydrogen peroxide, and 40 ml (60 °C) of deionized water (the solid-liquid ratio of the cathode material to deionized water is 50 g / L) are added. The ball milling process is carried out at a rotation speed of 600 r / min. Ball milling leaching is carried out for 10 min.

[0044] S3. Resource recovery: The leaching solution obtained in step S2 is subjected to solid-liquid separation through a vacuum filtration device to obtain a lithium-rich solution and residues.

[0045] Specifically, the leaching solution is subjected to solid-liquid separation using a vacuum filtration device with a 0.45 μm filter membrane and a suction filtration pressure of 0.1 Mpa to obtain a lithium-rich solution and residues.

[0046] A preparation method of lithium carbonate, the above lithium-rich solution is evaporated and crystallized in a water bath heating device at 80 °C, and then the crystallization product is heated to 500 °C at a heating rate of 5 °C / min in an air atmosphere and calcined for 2 h to obtain Li2CO3.

[0047] A preparation method of an oxygen evolution catalyst for electrolyzing water, the above residues are washed 3 times with deionized water and then heated to 600 °C at a rate of 10 °C / min and calcined for 2 h in an air atmosphere to prepare an efficient oxygen evolution catalyst for electrolyzing water.

[0048] Example 2

[0049] A method for recovering metal elements in waste ternary lithium batteries,

[0050] Same as the scheme of Example 1, the difference is that the cathode material in step S1 is Li(Ni 0.6 Co 0.2 Mn 0.2 )O2.

[0051] Example 3

[0052] A method for recovering metal elements from waste ternary lithium batteries

[0053] Same as the solution in Example 1, except that in step S1, the cathode material is Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2.

[0054] Example 4

[0055] A method for recovering metal elements from waste ternary lithium batteries

[0056] Same as the solution in Example 1, except that in step S1, the cathode material is Li(Ni 0.8 Co 0.1 Mn 0.1 )O2.

[0057] Example 5

[0058] A method for recovering metal elements from waste ternary lithium batteries

[0059] Same as the solution in Example 1, except that in step S2, the mass ratio of oxalic acid to the cathode material is 3:1. That is, the mass of oxalic acid is 6 g.

[0060] Example 6

[0061] A method for recovering metal elements from waste ternary lithium batteries

[0062] Same as the solution in Example 1, except that in step S2, the temperature of deionized water is 80 °C.

[0063] Example 7

[0064] A method for recovering metal elements from waste ternary lithium batteries

[0065] Same as the solution in Example 1, except that in step S2, the solid-liquid ratio is 100 g / L. That is, the cathode material after S1 activation is 4 g.

[0066] Example 8

[0067] A method for recovering metal elements from waste ternary lithium batteries

[0068] Same as the solution in Example 1, except that in step S3, the calcination temperature of the residue is 400 °C.

[0069] Example 9

[0070] A method for recovering metal elements from waste ternary lithium batteries

[0071] Same as the solution in Example 1, except that in step S1, the calcination time is 80 min.

[0072] Example 10

[0073] A method for recovering metal elements from waste ternary lithium batteries

[0074] Same as the solution in Example 1, the difference is that the calcination time in step S1 is 40 min

[0075] Example 11

[0076] A method for recovering metal elements from waste ternary lithium batteries

[0077] Same as the solution in Example 1, the difference is that the calcination temperature in step S1 is 400 °C

[0078] Example 12

[0079] A method for recovering metal elements from waste ternary lithium batteries

[0080] Same as the solution in Example 1, the difference is that the calcination temperature in step S1 is 200 °C

[0081] Example 13

[0082] A method for recovering metal elements from waste ternary lithium batteries

[0083] Same as the solution in Example 1, the difference is that the ball milling time in step S1 is 70 min

[0084] Example 14

[0085] A method for recovering metal elements from waste ternary lithium batteries

[0086] Same as the solution in Example 1, the difference is that the ball milling time in step S1 is 50 min

[0087] Example 15

[0088] A method for recovering metal elements from waste ternary lithium batteries

[0089] Same as the solution in Example 1, the difference is that the mass of the ball milling beads in step S1 is 100 g. That is, the mass ratio of the ball milling beads to the cathode material is 25:1

[0090] Comparative Example 1

[0091] A method for recovering metal elements from waste ternary lithium batteries

[0092] Same as the solution in Example 1, the difference is that step S1 is not carried out

[0093] Comparative Example 2

[0094] A method for recovering metal elements from waste ternary lithium batteries

[0095] Same as the solution of Embodiment 1, the difference is that in step S2, stirring at 80 °C is used instead of ball milling.

[0096] Comparative Example 3

[0097] A method for recovering metal elements from waste ternary lithium batteries, comprising the following steps:

[0098] S0. Pretreatment: Discharge, disassemble, crush the waste ternary lithium battery, and separate to obtain the positive electrode material powder.

[0099] Specifically, first completely discharge the waste ternary lithium battery on a self-made lighting device and disassemble it in a fume hood.

[0100] Separate the components such as the negative electrode, positive electrode, plastic separator, and housing. Clean and dry the positive electrode, and then put it into a high-speed universal grinder for mechanical and physical crushing. Use a 200-mesh sieve to separate the aluminum foil and the positive electrode material powder. Use deionized water as the medium and perform ultrasonic treatment in an ultrasonic device to separate the copper foil and graphite.

[0101] S1. Leaching: The cathode material, eutectic solvent, and grinding aid (mesoporous (α-SiO2·H2O)x·(Al2O3)y microspheres (x = 0.1 - 0.9, y = 1 - x)) are mixed at a certain solid-liquid ratio and added to a stainless-steel ball mill jar. A certain mass of steel balls is added and ball milled at a certain rotational speed to obtain a leaching solution. Specifically, first, the eutectic solvent is prepared: Choline chloride and ethylene glycol with a molar ratio of 1:2 are mixed in a beaker and magnetically stirred at 80 °C for 60 min. The obtained eutectic solvent is named choline chloride-ethylene glycol. Preparation of the grinding aid (mesoporous (α-SiO2·H2O)x·(Al2O3)y microspheres (x = 0.1 - 0.9, y = 1 - x)): The reaction is carried out in a 250 ml flask at 35 °C with magnetic stirring at a rotational speed of 300 rpm. First, solution I containing KCl (0.0015 g), ethanol (38 ml), water (6 ml), and ammonia water (3 ml) is added to the 250 mL flask and magnetically stirred at 35 °C and a rotational speed of 300 rpm. Then, solution II containing 58 ml of ethanol, 5.64 g of tetraethyl orthosilicate, and 5.06 g of ammonium aluminum sulfate is continuously added to the flask within 2 hours using a syringe pump. After further reacting for 15 hours, the obtained microspheres are centrifuged and purified, and washed 3 times with ethanol. Finally, the microspheres are vacuum dried at room temperature. Then, 2 g of the cathode material powder, 120 mg of the grinding aid (mesoporous (α-SiO2·H2O)x·(Al2O3)y microspheres (x = 0.1 - 0.9, y = 1 - x)), and 40 ml of choline chloride-ethylene glycol are physically mixed (solid-liquid ratio 50 g / L), and then added to a 100 ml stainless-steel ball mill jar containing 60 g of steel balls and ball milled at 600 rpm for 30 min, 60 min, and 120 min. After the ball milling is completed, a leaching solution is obtained.

[0102] S2. Precipitation: The leaching solution is filtered and separated to obtain a filtrate and a filter residue. NaOH and Na2CO3 are added to the filtrate to stepwise precipitate Ni, Co, Mn, and Li in the filtrate. Specifically, first, deionized water is slowly added to the filtrate. When the filtrate becomes colorless, 0.5 M NaOH solution is added to adjust the pH of the filtrate to 10, and then magnetic stirring is carried out for 30 min. After the reaction, centrifugal separation is carried out to obtain a Li-containing solution and a precipitate. The precipitate is washed 3 times with deionized water and then dried at 60 °C for 12 h to obtain Me(OH)2 (Me = Ni, Co, Mn). The Li-containing solution is heated in a water bath to 90 °C, 0.5 M Na2CO3 is added, and after reacting for 60 min, centrifugal separation is immediately carried out to obtain a white precipitate of Li2CO3. S3. Calcination: Me(OH)2 (Me = Ni, Co, Mn) is calcined at 500 - 700 °C for 3 - 6 h to obtain metal oxides of Ni, Co, and Mn. Specifically, Me(OH)2 (Me = Ni, Co, Mn) is calcined at 600 °C for 5 h to obtain metal oxides.

[0103] Comparative Example 4

[0104] A method for recovering metal elements from waste ternary lithium batteries

[0105] Same as the scheme of Example 1, the difference is that the calcination in step S1 is not included.

[0106] Comparative Example 5

[0107] A method for recovering metal elements from waste ternary lithium batteries

[0108] Same as the scheme of Example 1, the difference is that the ball milling in step S1 is not included.

[0109] Performance test

[0110] (1) XRD test:

[0111] Figure 1 The XRD pattern of the Li2CO3 obtained in Example 1 compared with the standard card. From Figure 1 It can be seen that the Li2CO3 obtained in Example 1 of the present invention has a very high purity.

[0112] Figure 2 The XRD patterns of the waste lithium-ion battery cathode material before and after pretreatment in Example 1. From Figure 2 It can be seen that after the waste lithium-ion battery cathode material is pretreated by the present invention, the crystal structure is damaged.

[0113] (2) BET test: Figure 3BET spectra of the spent lithium-ion battery cathode material before and after pretreatment in Example 1. After calculation by the BET equation, the specific surface area of the spent lithium-ion battery cathode material increased from 2.4436 m 2 / g to 6.4916 m 2 / g after pretreatment with the present invention, forming a porous and loose material.

[0114] (3) Surface energy test: After pretreatment with the present invention, the surface energy of the spent lithium-ion battery cathode material increased from 18.9 mN / m to 53.5 mN / m, indicating that after pretreatment with the present invention, the surface energy of the spent lithium-ion battery cathode material increased, which is beneficial to accelerating the solid-liquid interfacial reaction during acid leaching.

[0115] (4) Lithium leaching rate and selectivity test:

[0116] Take 1 ml of the leaching solution from the ball mill pot, filter it immediately after sampling and dilute it 10 times for quantitative analysis of metal ion concentration.

[0117] The leaching efficiency and selectivity of lithium are calculated by the following two formulas:

[0118]

[0119] Among them, C t , V, m and ω represent the concentration (g / L) of the target metal in the lithium-rich solution, the volume (L) of the lithium-rich solution, the mass (g) of the cathode material, and the mass fraction (%) of the target metal in the cathode material at different reaction times, respectively; C M , C Li , C Ni , C Co and C Mn represent the concentrations (g / L) of the target metal, lithium, nickel, cobalt and manganese in the lithium-rich solution, respectively.

[0120] The lithium leaching rate and selectivity data of each example and comparative example are shown in Table 1 below.

[0121] Table 1

[0122]

[0123]

[0124] (5) Electrolytic water test:

[0125] The residues obtained in Example 1 and Example 8 were used as oxygen evolution catalysts for electrolytic water, and their oxygen evolution performance was tested. An electrochemical workstation was used to test the oxygen evolution catalytic performance of the electrodes prepared from each catalyst. A three-electrode system was adopted, where the counter electrode was a platinum sheet electrode, the reference electrode was a Hg / HgO electrode, and the electrolyte was an aqueous KOH solution with a concentration of 1 mol / L.

[0126] Figure 4 Figure 4 shows the linear sweep voltammetry (LSV) curve and Tafel curve when the residue of Example 1 was used as the oxygen evolution catalyst for electrolytic water.

[0127] Figure 5 Figure 8 shows the linear sweep voltammetry (LSV) curve and Tafel curve when the residue of Example 8 was used as the oxygen evolution catalyst for electrolytic water.

[0128] From Figure 4 and Figure 5 it can be seen that when the current density was 10 mA / cm 2 , the overpotential of the residue of Example 1 as the oxygen evolution catalyst for electrolytic water was 264 mV, and the overpotential of the residue of Example 8 as the oxygen evolution catalyst for electrolytic water was 280 mV. The overpotential of the oxygen evolution catalyst obtained in Example 1 was lower, indicating more excellent oxygen evolution catalytic performance. The Tafel slope of the residue of Example 1 as the oxygen evolution catalyst for electrolytic water was 77.96 mV / dec, and the Tafel slope of the residue of Example 8 as the oxygen evolution catalyst for electrolytic water was 81.36 mV / dec. The Tafel slope of the oxygen evolution catalyst obtained in Example 1 was lower, indicating more excellent oxygen evolution catalytic performance.

[0129] In summary, the present invention efficiently recovers lithium from waste ternary lithium batteries by mechanochemical method. Under the condition of a solid-liquid ratio of 100 g / L, nearly complete lithium leaching efficiency can be achieved within 10 min, and the leaching efficiency can be as high as 83-99%, and the selectivity can be as high as 92-97%. Even under the harsh condition of a high solid-liquid ratio (100 g / L), the lithium leaching efficiency and selectivity still remained at excellent levels of 84% and 93% respectively. By heat-treating the residue, the present invention systematically studied the effect of calcination temperature on the material properties, and found that the residue calcined at the optimal temperature in Example 1 exhibited excellent catalytic performance for the oxygen evolution reaction, with an overpotential as low as 264 mV (10 mA / cm 2 ), and the Tafel slope was only 77.96 mV / dec, significantly superior to the commercial Co3O4 catalyst, realizing the high-value utilization of the residue.

[0130] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for recovering metal elements in waste ternary lithium batteries, characterized in that, It includes the following steps: S1. Pretreatment: successively calcine and ball-mill and activate the waste lithium-ion battery cathode material; S2. Mechanochemical leaching: after leaching by ball-milling the cathode material activated in S1, oxalic acid, reducing agent and deionized water with ball-milling beads to obtain a leaching solution; S3. Solid-liquid separation of the leaching solution obtained in step S2 to obtain a lithium-rich solution and residues; Among them, in step S1, the positive electrode material is Li(Ni x Co y Mn z )O2, where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1; Among them, in step S2, the solid-liquid ratio of the cathode material activated in S1 to deionized water is 10-100 g / L.

2. The method for recycling metal elements in waste ternary lithium batteries according to claim 1, wherein, In step S1, the calcination temperature is 200-400 °C and the calcination time is 20-100 min.

3. The method for recycling metal elements in waste ternary lithium batteries according to claim 1, wherein, In step S1, the ball-milling time is 10-100 min, the ball-milling speed is 300-600 r / min, and the mass ratio of ball-milling beads to the cathode material is (5-25):

1.

4. The method for recycling metal elements in waste ternary lithium batteries according to claim 1, wherein In step S2, the mass ratio of oxalic acid to the cathode material is (0.1-3):

1.

5. The method for recovering metal elements in waste ternary lithium batteries according to claim 1 is characterized in that, In step S2, the reducing agent is one or more of sodium sulfite, ferrous sulfate, hydrogen peroxide, ascorbic acid.

6. The recovery method of metal elements in waste ternary lithium batteries according to claim 1, characterized in that In step S2, the mass ratio of the cathode material activated in S1 to ball-milling beads is 1:(10-50).

7. The recycling method of metal elements in waste ternary lithium batteries according to claim 1, wherein In step S2, the temperature of the deionized water is 25-90 °C.

8. The method for recycling metal elements in waste ternary lithium batteries according to claim 1, wherein, In step S2, the ball-milling time is 3-90 min and the ball-mill speed is 300-700 r / min.

9. A method for preparing lithium carbonate, characterized in that, It includes the following steps: evaporate and crystallize the lithium-rich solution obtained by the method for recovering metal elements in the waste ternary lithium battery according to any one of claims 1-8, and perform calcination treatment to obtain Li2CO3.

10. A preparation method of an oxygen evolution catalyst for electrolyzing water, characterized in that, It includes the following steps: calcine the residues obtained by the method for recovering metal elements in the waste ternary lithium battery according to any one of claims 1-8 at 200-800 °C to prepare an oxygen evolution catalyst for electrolyzing water.

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