Leaching agent and leaching method for valuable metal in lithium battery positive electrode material

Abstract

The invention provides a leaching agent and a leaching method for valuable metals in a lithium battery positive electrode material, and belongs to the technical field of lithium battery recovery. The leaching agent comprises polymer binary acid which is in a liquid state at normal temperature, and the polymer binary acid is selected from one or more of double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol and double-end carboxyl polybutylene glycol. The leaching method comprises the following steps: mixing the lithium battery positive electrode material with the leaching agent, and carrying out leaching reaction to obtain a solution containing valuable metal ions. The leaching agent provided by the invention has a good leaching effect on valuable metals in the lithium battery positive electrode material, the required leaching temperature is low, the leaching speed is high, and the corrosion to equipment is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery recycling, and in particular relates to a leaching agent and a leaching method for valuable metals in lithium battery positive electrode materials. Background Art

[0002] With the booming development of portable electronic devices and the new energy vehicle industry, the number of used lithium-ion batteries has increased dramatically year by year. Recovering valuable metals (nickel, cobalt, manganese, lithium, etc.) from used lithium-ion batteries can effectively alleviate the problems of resource waste and environmental pollution caused by used lithium-ion batteries.

[0003] Pyrometallurgical and wet recycling processes are well-established and are currently the most commonly used methods for recycling spent lithium-ion batteries. The wet recycling process uses a leaching agent to extract the valuable metal ions from the lithium-ion battery's cathode material, followed by elemental separation and material regeneration to achieve the recovery of spent lithium-ion battery cathode materials. Leaching agents used in the wet recycling process include inorganic acids, organic acids, and a new green solvent, deep eutectic solvents.

[0004] Deep eutectic solvents usually include hydrogen bond acceptors and hydrogen bond donors. Using them to recycle spent lithium-ion batteries does not emit acidic wastewater, harmful gases or volatile organic compounds, and can leach metals over a wider temperature range. However, the hydrogen bond acceptor substances, such as choline chloride quaternary ammonium salts, will form halide anions Cl after absorbing water. - , which can cause severe corrosion to steel equipment. Furthermore, to maintain a uniform liquid state, hydrogen bond donors such as carboxylic acids and alcohols require a backbone with ≤5 carbon atoms. This is because the melting points of hydrogen bond donors and hydrogen bond acceptors increase with the number of carbon atoms in the backbone. This severely limits the selection of raw materials for deep eutectic solvents and hinders their development. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a leaching agent and method for leaching valuable metals from lithium battery positive electrode materials. The leaching agent provided by the present invention exhibits excellent leaching efficiency for valuable metals in lithium battery positive electrode materials, requires low leaching temperatures, has a fast leaching rate, and exhibits low corrosion to equipment.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a leaching agent for valuable metals in a positive electrode material of a lithium battery, wherein the leaching agent comprises a polymer dibasic acid that is liquid at room temperature, and the polymer dibasic acid is selected from one or more of double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol, and double-end carboxyl polybutylene glycol.

[0008] The present invention has found through research that double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol and double-end carboxyl polybutylene glycol, which are liquid at room temperature, can react with the valuable metals in the positive electrode material of lithium batteries alone without the assistance of hydrogen bond acceptors and reducing agents to leach the metals. Compared with small molecule dibasic acids, liquid double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol and double-end carboxyl polybutylene glycol have longer molecular chains, which extend the distance between the two carboxyl groups at the end, limit the intramolecular hydrogen bonding between the carboxyl groups, and allow the carboxyl groups to undergo more intermolecular hydrogen bonding, thereby being able to react more with the valuable metals in the positive electrode material of lithium batteries; in addition, there are a large number of ether bonds in the molecular chain, and the active O atoms in the ether bonds can coordinate with the metals, thereby increasing the metal leaching rate. The present invention uses the above-mentioned polymer as a leaching agent for the valuable metals in the positive electrode material of lithium batteries, which not only has a high leaching rate, a low required leaching temperature and a fast leaching speed, but also has lower corrosiveness than the small molecule organic acids used in conventional deep eutectic solvents.

[0009] In some embodiments of the present invention, the degree of polymerization of the polymer dibasic acid is independently 50-300, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300, preferably 150-250, more preferably 200.

[0010] Through research, the present invention has found that when the degree of polymerization of double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol, and double-end carboxyl polybutylene glycol is 50-300, they have a good leaching effect on valuable metals in lithium battery positive electrode materials, and the leaching effect is best when the degree of polymerization is 200. When the degree of polymerization is lower than 50 or greater than 300, the above polymers will gradually transform from liquid to solid, and the leaching effect will be significantly reduced.

[0011] In some embodiments of the present invention, the leaching agent further comprises a hydrogen bond acceptor.

[0012] Through research, the present invention has found that double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol, and double-end carboxyl polybutylene glycol can also replace small molecule organic acids as hydrogen bond donors, cooperate with hydrogen bond acceptors to form a deep eutectic solvent, and are used as leaching agents for valuable metals in lithium battery positive electrode materials. This leaching agent not only has a valuable metal leaching effect comparable to or better than that of a deep eutectic solvent using a small molecule dibasic acid, but also has lower corrosivity (when the molar ratio of hydrogen bond donor to hydrogen bond acceptor remains unchanged, the molecular weight of the polymer dibasic acid hydrogen bond donor is larger, the mass proportion is higher, and the mass proportion of the hydrogen bond acceptor is lower, which can reduce the mass content of corrosive hydrogen bond acceptors such as choline chloride, and the corrosivity of the polymer dibasic acid is also lower than that of the small molecule organic acid).

[0013] In some embodiments of the present invention, the hydrogen bond acceptor is selected from one or more of quaternary ammonium salts, amine compounds, amide compounds, halogen-containing compounds and aromatic compounds containing hydrogen bond acceptor groups.

[0014] In some embodiments of the present invention, the hydrogen bond acceptor is selected from one or more of choline chloride, phosphorylcholine, betaine, lactic acid and tetrabutylammonium bromide.

[0015] In some embodiments of the present invention, the ratio of the molar amount of the polymer dibasic acid to the molar amount of the hydrogen bond acceptor is 1:(1-4), for example, it can be 1:1, 1:1.2, 1:1.3, 1:1.5, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.3, 1:2.5, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.3, 1:3.5, 1:3.6, 1:3.8 or 1:4, etc.; preferably 1:2.

[0016] In a second aspect, the present invention provides a method for leaching valuable metals from a lithium battery positive electrode material, the leaching method comprising the following steps:

[0017] The positive electrode material of the lithium battery is mixed with the leaching agent described in the first aspect, and a leaching reaction is carried out to obtain a solution containing valuable metal ions.

[0018] In some embodiments of the present invention, the mass ratio of the lithium battery positive electrode material to the leaching agent is 1:(10-30); for example, it can be 1:10, 1:12, 1:13, 1:15, 1:16, 1:18, 1:20, 1:22, 1:23, 1:25, 1:26, 1:28 or 1:30, etc.

[0019] In some embodiments of the present invention, the temperature of the leaching reaction is above 60°C, for example, it can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C, etc.; preferably, it can be 80-120°C.

[0020] In some embodiments of the present invention, the leaching reaction time is more than 15 minutes, for example, it can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes, etc.; preferably, it is 30-60 minutes.

[0021] In some embodiments of the present invention, the leaching reaction is carried out under stirring conditions.

[0022] In some embodiments of the present invention, the stirring speed is 300-1000 rpm; for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm, etc.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses one or more of double-terminated carboxyl polyethylene glycol, double-terminated carboxyl polypropylene glycol, and double-terminated carboxyl polybutylene glycol, all of which are liquid at room temperature, as leaching agents for valuable metals in lithium battery positive electrode materials. Alternatively, the aforementioned polymer dibasic acids are combined with hydrogen bond acceptors to form a deep eutectic solvent, which serves as a leaching agent for valuable metals in lithium battery positive electrode materials. Compared to conventional deep eutectic solvent leaching agents containing small molecule organic acids, the leaching agent provided by the present invention not only has comparable or better valuable metal leaching effects, but also requires a low leaching temperature, has a fast leaching rate, and is less corrosive to equipment. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the specific embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0026] The NCM811 positive electrode material powder used in the embodiment of the present invention is recovered according to the following method:

[0027] The NCM811 soft-pack battery of the waste high-nickel graphite system was immersed in a 1 mol / L NaCl solution for 24 hours to achieve complete self-discharge, then dried in an 80°C oven for 8 hours, cooled to room temperature, and then the positive and negative electrodes, diaphragms and aluminum-plastic film shells were disassembled and separated; the positive electrode was dissolved in a 10wt% NaOH solution for 5 hours (solid-liquid ratio of 100g / L), and after the reaction was completed, it was filtered and dried. The dried powder was calcined in a muffle furnace at 650°C for 4 hours to obtain NCM811 positive electrode material powder.

[0028] The preparation method of the double-terminated carboxyl polyethylene glycol used in the embodiment of the present invention is as follows:

[0029] Polyethylene glycol and an oxidizing agent, sodium chlorite, are mixed in a molar ratio of 1:1. A catalyst, dimethylaminopyridine, is added at a catalyst amount of 5% by weight of the polyethylene glycol. Adipic acid is added to adjust the pH of the system to 7-8. The reaction is carried out at 40°C to convert the primary hydroxyl groups at both ends into carboxyl groups, thereby obtaining a double-carboxyl-terminated polyethylene glycol. The degree of polymerization (n) of the double-carboxyl-terminated polyethylene glycol is calculated based on the number average molecular weight of the polyethylene glycol.

[0030] Example 1

[0031] This embodiment provides a leaching agent for valuable metals in a lithium battery positive electrode material, which is double-terminated carboxyl polyethylene glycol (degree of polymerization n=200).

[0032] This embodiment also provides a method for leaching valuable metals from a lithium battery positive electrode material, comprising the following steps:

[0033] The NCM811 cathode material powder and the leaching agent provided in this embodiment were added to a three-necked flask in a mass ratio of 1:20, and heated to react at 80° C. for 30 min. During the reaction, the magnetic stirring speed was maintained at 600 rpm to obtain a solution containing Li, Ni, Co, and Mn ions.

[0034] Example 2-13

[0035] Examples 2-13 each provide a leaching agent and leaching method for valuable metals in a lithium battery positive electrode material. The only difference from Example 1 is that the degree of polymerization, reaction temperature, reaction time, and stirring rate of the double-terminated carboxyl polyethylene glycol are different, as shown in Table 1.

[0036] Leaching rate test:

[0037] A digestion reagent consisting of 68 wt% HNO3 solution, 36 wt% HCl solution, 40 wt% HF solution, and 70 wt% HCIO4 solution in a volume ratio of 2:1:1:1 was used to completely digest the NCM811 cathode material powder, and the metal ion concentration was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES) to obtain the actual metal element content of the NCM811 cathode material powder;

[0038] A 68 wt % concentrated nitric acid solution was mixed with water in a volume ratio of 2:100 to prepare a dilute nitric acid solution, and the solution after leaching in the above embodiment was diluted with the dilute nitric acid solution to the measurement range of ICP-OES. The metal ion concentration therein was measured by ICP-OES to obtain the amount of leached metal ions;

[0039] The ratio of the amount of leached metal ions to the actual metal element content of the NCM811 cathode material powder is the metal leaching rate. The above leaching rate test results are shown in Table 1.

[0040] Table 1

[0041]

[0042] The test results in Table 1 show that dual-carboxyl-terminated polyethylene glycol can react independently with valuable metals in lithium battery cathode materials, leaching metal ions. When the degree of polymerization (DP) of the dual-carboxyl-terminated polyethylene glycol is between 50 and 300, the leaching rate can reach over 85%, with the DP of 200 achieving the best leaching effect. When the DP is below 50 or above 300, the leaching rate decreases significantly as the dual-carboxyl-terminated polyethylene glycol gradually transforms from a liquid to a solid state.

[0043] Example 14

[0044] This embodiment provides a leaching agent for valuable metals in a lithium battery positive electrode material, which is composed of double-terminal carboxyl polyethylene glycol (degree of polymerization = 200) and choline chloride in a molar ratio of 1:2.

[0045] This embodiment also provides a method for leaching valuable metals from a lithium battery positive electrode material, comprising the following steps:

[0046] The NCM811 cathode material powder and the leaching agent provided in this embodiment were added to a three-necked flask in a mass ratio of 1:20, and heated to react at 80° C. for 30 min. During the reaction, the magnetic stirring speed was maintained at 600 rpm to obtain a solution containing Li, Ni, Co, and Mn ions.

[0047] Examples 15-23

[0048] Examples 15-23 each provide a leaching agent and leaching method for valuable metals in a lithium battery positive electrode material. The only difference from Example 14 is the degree of polymerization n value of the double-ended carboxyl polyethylene glycol, the mass ratio of the positive electrode material powder to the leaching agent, and / or the hydrogen bond acceptor, as shown in Table 2.

[0049] Comparative Examples 1-3

[0050] Comparative Examples 1-3 each provide a leaching agent and leaching method for valuable metals in a lithium battery positive electrode material, which differ from Example 14 only in that the hydrogen bond donor and / or hydrogen bond acceptor is different, as shown in Table 2.

[0051] Table 2

[0052]

[0053] As can be seen from the test results in Table 2, under the same conditions, the leaching agents using double-ended carboxyl polyethylene glycol as hydrogen bond donors (Examples 14-23) have comparable or better metal leaching effects than the leaching agents using small molecule dibasic acid hydrogen bond donors (Comparative Example). Since the molecular weight of double-ended carboxyl polyethylene glycol is much greater than that of small molecule dibasic acids, the mass content of corrosive hydrogen bond acceptors such as choline chloride in the leaching agents provided by Examples 14-22 is lower; in addition, the acidity of double-ended carboxyl polyethylene glycol is also lower than that of small molecule dibasic acids. In other words, by using double-ended carboxyl polyethylene glycol instead of small molecule dibasic acids as hydrogen bond donors, the leaching agents obtained in the present invention reduce corrosivity while maintaining comparable or better metal leaching effects.

[0054] The foregoing description is intended only to provide specific embodiments of the present disclosure, intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments described herein, but rather to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A leaching agent for valuable metals in lithium battery positive electrode materials, characterized in that: The leaching agent comprises a polymer dibasic acid which is liquid at room temperature, and the polymer dibasic acid is selected from one or more of double-end carboxyl polyethylene glycol, double-end carboxyl polypropylene glycol and double-end carboxyl polybutylene glycol.

2. The leaching agent according to claim 1, characterized in that The degree of polymerization of the polymer dibasic acid is 50-300, preferably 150-250, more preferably 200.

3. The leaching agent according to claim 1 or 2, characterized in that The leachant also includes a hydrogen bond acceptor.

4. The leaching agent according to claim 3, characterized in that The hydrogen bond acceptor is selected from one or more of quaternary ammonium salts, amine compounds, amide compounds, halogen-containing compounds and aromatic compounds containing hydrogen bond acceptor groups.

5. The leaching agent according to claim 3 or 4, characterized in that The hydrogen bond acceptor is selected from one or more of choline chloride, phosphorylcholine, betaine, lactic acid and tetrabutylammonium bromide.

6. The leaching agent according to any one of claims 3 to 5, characterized in that The ratio of the molar amount of the polymer dibasic acid to the molar amount of the hydrogen bond acceptor is 1:(1-4), preferably 1:

2.

7. A method for leaching valuable metals from a lithium battery positive electrode material, characterized in that: The leaching method comprises the following steps: The lithium battery positive electrode material is mixed with the leaching agent according to any one of claims 1 to 6, and a leaching reaction is carried out to obtain a solution containing valuable metal ions.

8. The leaching method according to claim 7, characterized in that The mass ratio of the lithium battery positive electrode material to the leaching agent is 1:(10-30).

9. The leaching method according to claim 7 or 8, characterized in that The leaching reaction temperature is above 60°C, preferably 80-120°C; Preferably, the leaching reaction time is more than 15 minutes, preferably 30-60 minutes.

10. The leaching method according to any one of claims 7 to 9, characterized in that: The leaching reaction is carried out under stirring conditions; Preferably, the stirring speed is 300-1000 rpm.

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