Method for recycling positive electrode material of waste lithium battery based on double circulation of low-viscosity deep eutectic solvent

Abstract

The invention provides a method for double-circulation recovery of a waste lithium battery positive electrode material based on a low-viscosity deep eutectic solvent, and belongs to the technical field of recovery and regeneration of waste lithium ion battery materials. Based on a eutectic system of 1-butyl-3-methylimidazolium chloride and oxalic acid, the viscosity of the deep eutectic solvent is improved through a non-solvated diluent, so that the ion leaching efficiency and the solid-liquid separation efficiency are improved, water is added into the leachate to induce precipitation of an oxalate precursor, and dehydration is performed to realize regeneration of the deep eutectic solvent. The comprehensive recovery efficiency of the low-viscosity deep eutectic solvent to lithium, nickel, cobalt and manganese is 90% or above, the low-viscosity deep eutectic solvent can be repeatedly used, the problem that the deep eutectic solvent cannot be used for multiple times is solved, the investment cost of the deep eutectic solvent in lithium battery recovery is reduced, secondary pollutants in the recovery process are avoided, and the method is suitable for industrial production. Good application prospects are realized.

Description

Technical Field

[0001] The invention relates to the technical field of recycling and regenerating waste lithium-ion battery materials, and in particular to a method for recycling waste lithium battery positive electrode materials based on a low-viscosity deep eutectic solvent double circulation. Background Art

[0002] The rapid expansion of the consumer market for electric vehicles and electronic products has led to an exponential growth in the demand for lithium-ion batteries, which has brought about a huge market size for the recycling of waste batteries. At present, the recycling methods for waste lithium battery cathode materials mainly include hydrometallurgy and pyrometallurgy. Among them, deep eutectic solvents (DES) stand out as a green alternative leaching agent in the extraction and recovery of precious metal ions in hydrometallurgy. DES has excellent performance in dissolving metal oxides without the use of reducing agents, oxidizing agents or expensive extractants. In the application of DES to recover lithium battery cathode materials, the driving force for metal extraction mainly depends on the anion (usually Cl - ) with metal ions, and the reducing ability of DES. The high viscosity of DES will endanger the mass transfer of dissolved substances during the leaching / separation process, resulting in poor extraction effect. In addition, the high viscosity makes the separation efficiency of the leachate and solid impurities low, resulting in the loss of leachate and recyclable components. In addition, the process of extracting metal ions from the leachate in most current processes often causes fatal damage to the deep eutectic solvent and cannot be recycled, which will undoubtedly increase the cost of using DES. Summary of the invention

[0003] In view of the above deficiencies in the prior art, the present invention provides a method for double-circulation recovery of waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvents. The present invention uses recyclable low-viscosity deep eutectic solvents to regenerate lithium battery positive electrode materials, which solves the problem that deep eutectic solvents cannot be used multiple times, reduces the cost of deep eutectic solvents in lithium battery recycling, and avoids the generation of secondary pollutants during the recycling process.

[0004] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0005] A method for recycling waste lithium battery positive electrode materials based on a low-viscosity deep eutectic solvent double cycle, comprising the following steps:

[0006] (1) A low-viscosity deep eutectic solvent is prepared using 1-butyl-3-methylimidazolium chloride, oxalic acid and a diluent as raw materials; wherein 1-butyl-3-methylimidazolium chloride is a hydrogen bond acceptor and oxalic acid is a hydrogen bond donor;

[0007] (2) Mixing the waste battery positive electrode material with a low-viscosity deep eutectic solvent, and heating at 60-120 °C for 60-180 min to obtain a mixed solution;

[0008] (3) separating the mixed solution to obtain a leaching solution containing cobalt and manganese ions and a solid mixture containing lithium oxalate and nickel oxalate;

[0009] (4) adding water to the solid mixture in step (3), dispersing the mixture, and separating the mixture to obtain an aqueous solution containing lithium oxalate and a paste-like salt layer of nickel oxalate; adding water to the leaching solution in step (3), allowing the mixture to precipitate naturally, and separating the solid cobalt oxalate, the solid manganese oxalate, and the clear solution;

[0010] (5) supplementing the clear solution in step (4) with oxalic acid and performing high-temperature dehydration to obtain a regenerated low-viscosity deep eutectic solvent; dehydrating the aqueous solution of lithium oxalate in step (4) to obtain lithium oxalate crystals; washing and purifying the paste salt layer nickel oxalate in step (4) to obtain nickel oxalate crystals;

[0011] (6) The solid cobalt oxalate and solid manganese oxalate in step (4) and the lithium oxalate crystals and nickel oxalate crystals in step (5) are mixed in proportion and calcined to obtain a regenerated positive electrode material.

[0012] Preferably, in step (1), the molar ratio of 1-butyl-3-methylimidazolium chloride to oxalic acid is 4:1 to 1:1.

[0013] Preferably, in step (1), the diluent is propylene carbonate.

[0014] Preferably, in step (1), the amount of the diluent added is 10% to 30% of the total mass of the low-viscosity deep eutectic solvent, and the shear viscosity of the low-viscosity deep eutectic solvent is less than 40 Pa·s.

[0015] Preferably, in step (2), the mass ratio of the low viscosity deep eutectic solvent to the waste battery positive electrode material is 50:1 to 100:1.

[0016] Preferably, in step (2), the heating temperature is 90° C. and the heating time is 180 min.

[0017] Preferably, in step (4), in the precipitation of the leachate with water, the mass ratio of water to the leachate is 0.3:1 to 0.5:1.

[0018] Preferably, in step (5), the temperature of the high temperature dehydration is 80-100°C.

[0019] Preferably, in step (6), the calcination temperature is 800-1000°C, the calcination time is 12-24 h, and the calcination environment is aerobic conditions or air conditions.

[0020] The method for leaching cobalt and manganese ions of the present invention relates to the following principles: high-valent metal ions are reduced to low-valent metals by oxalic acid, cobalt and manganese ions coordinate with anions to form metal chloride complexes that are dissolved in a low-viscosity deep eutectic solvent, and nickel and lithium ions form insoluble metal salt precipitations with oxalic acid; in the precipitation recovery of cobalt and manganese ions, the principle relates to the following principles: the metal chloride complex structure is destroyed by water molecules to form cobalt oxalate and manganese oxalate precipitations; the collected lithium oxalate, nickel oxalate, cobalt oxalate and manganese oxalate are mixed and ball-milled according to a specific element ratio, and then calcined at high temperature to obtain the corresponding regenerated positive electrode material; for example, the collected lithium oxalate, nickel oxalate, cobalt oxalate and manganese oxalate are ball-milled and calcined according to the element ratio of Li: Ni: Co: Mn = 1: 0.5: 0.2: 0.3 to obtain the target product NCM523.

[0021] Compared with the prior art, the present invention is beneficial in that:

[0022] (1) The present invention starts from the properties of low-viscosity deep eutectic solvents and the ion leaching recovery route, adopts the eutectic system of 1-butyl-3-methylimidazolium chloride and oxalic acid, and improves the viscosity of the deep eutectic solvent by a non-solvating diluent to obtain a recyclable low-viscosity deep eutectic solvent. The low-viscosity deep eutectic solvent is used to recycle and reuse waste lithium battery positive electrode materials, thereby solving the problem that the deep eutectic solvent cannot be used multiple times, reducing the investment cost of the deep eutectic solvent in lithium battery recycling, and avoiding the generation of secondary pollutants during the recycling process.

[0023] (2) The double-circulation process of the present invention is fast, efficient, low-cost and pollution-free, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process flow chart of the method for recycling and regenerating waste battery positive electrode materials using a low-viscosity deep eutectic solvent according to the present invention;

[0025] Figure 2 is the leaching efficiency of deep eutectic solvent on waste battery cathode materials under different temperature conditions;

[0026] Figure 3 is the shear viscosity of the deep eutectic solvent at different propylene carbonate addition amounts;

[0027] Figure 4 is the precipitation efficiency of cobalt and manganese ions under different mass ratios of water to leachate;

[0028] Figure 5 To regenerate the leaching efficiency of low viscosity deep eutectic solvents;

[0029] Figure 6 This is the cycle performance diagram of the battery assembled using recycled positive electrode materials. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present invention provides a method for recycling waste lithium battery positive electrode materials based on a low-viscosity deep eutectic solvent double cycle, comprising the following steps:

[0032] (1) A low-viscosity deep eutectic solvent is prepared using 1-butyl-3-methylimidazolium chloride, oxalic acid and a diluent as raw materials; wherein 1-butyl-3-methylimidazolium chloride is a hydrogen bond acceptor and oxalic acid is a hydrogen bond donor;

[0033] (2) Mixing the waste battery positive electrode material with the deep eutectic solvent, and heating at 70-120 °C for 60-80 min to obtain a mixed solution;

[0034] (3) separating the mixed solution to obtain a leaching solution containing cobalt and manganese ions and a solid mixture containing lithium oxalate and nickel oxalate;

[0035] (4) adding water to the solid mixture in step (3), dispersing the mixture, and separating the mixture to obtain an aqueous solution containing lithium oxalate and a paste-like salt layer of nickel oxalate; adding water to the leaching solution in step (3), allowing the mixture to precipitate naturally, and separating the solid cobalt oxalate, the solid manganese oxalate, and the clear solution;

[0036] (5) supplementing the clear solution in step (4) with oxalic acid and performing high-temperature dehydration to obtain a regenerated low-viscosity deep eutectic solvent; dehydrating the aqueous solution of lithium oxalate in step (4) to obtain lithium oxalate crystals; washing and purifying the paste salt layer nickel oxalate in step (4) to obtain nickel oxalate crystals;

[0037] (6) The solid cobalt oxalate and solid manganese oxalate in step (4) and the lithium oxalate crystals and nickel oxalate crystals in step (5) are mixed in proportion and calcined to obtain a regenerated positive electrode material.

[0038] In some examples, in step (1), the molar ratio of 1-butyl-3-methylimidazolium chloride to oxalic acid is 4:1 to 1:1.

[0039] In some examples, in step (1), the amount of the diluent added is 10% to 30% of the total mass of the low viscosity deep eutectic solvent, and the shear viscosity of the low viscosity deep eutectic solvent is less than 40 Pa·s.

[0040] In some examples, in step (2), the mass ratio of the low viscosity deep eutectic solvent to the waste battery positive electrode material is 50:1 to 100:1.

[0041] In some examples, in step (4), in the precipitation of the leachate with water, the mass ratio of water to the leachate is 0.3:1~0.5:1.

[0042] In some examples, in step (5), the temperature of the high temperature dehydration is 80-100°C.

[0043] In some examples, in step (6), the calcination temperature is 800-1000° C., the calcination time is 12-24 hours, and the calcination environment is aerobic conditions or air conditions.

[0044] Example 1

[0045] A method for recycling waste lithium battery positive electrode materials based on a low-viscosity deep eutectic solvent double cycle, the steps are as follows:

[0046] (1) Preparation of deep eutectic solvent: weigh 17.4 g of 1-butyl-3-methylimidazolium chloride and 5 g of oxalic acid, stir at 80 °C for 20 min at a stirring speed of 200 r / min to form a colorless and transparent deep eutectic solvent;

[0047] (2) Leaching reaction: 1 g of waste battery positive electrode material powder was put into 30 g of deep eutectic solvent, stirred at 70-120 °C for 180 min, and filtered to separate the leachate. Figure 2 is the leaching efficiency of deep eutectic solvent on waste battery positive electrode materials under different temperature conditions; Figure 2 The optimal leaching temperature was selected as 90 ℃. After analysis, it was found that the leaching rate of cobalt and manganese ions was above 98% when stirring at 90 ℃.

[0048] (3) preparing a low-viscosity deep eutectic solvent: adding propylene carbonate in an amount of 10% to 50% of the total mass of the low-viscosity deep eutectic solvent to the deep eutectic solvent prepared in step (1), stirring at 60°C for 10 min to obtain a colorless and transparent low-viscosity deep eutectic solvent. Figure 3 is the shear viscosity of the deep eutectic solvent at different propylene carbonate addition amounts; Figure 3 The optimal addition amount of propylene carbonate is selected to be 15% of the total mass of the low viscosity deep eutectic solvent.

[0049] (4) Leaching-precipitation reaction: 1 g of waste battery positive electrode material powder was put into 30 g of low-viscosity deep eutectic solvent, stirred at 90 °C for 180 min, and filtered to separate the leaching solution containing cobalt and manganese ions and the solid mixture containing lithium oxalate and nickel oxalate. Analysis showed that the leaching rate of cobalt and manganese ions was above 99%.

[0050] (5) adding deionized water to the leachate in a mass ratio of deionized water to the leachate of 0.1:1 to 0.5:1, and filtering and separating to obtain solid cobalt oxalate, solid manganese oxalate, and a clear liquid; Figure 4 is the precipitation efficiency of cobalt and manganese ions under different mass ratios of deionized water and leaching solution; Figure 4 The optimal mass ratio of water to leachate is 0.35:1.

[0051] (5) Regeneration of low-viscosity deep eutectic solvent: Add 0.2 g oxalic acid to the clear solution and dehydrate it at 100 °C for 60 min to achieve regeneration of the low-viscosity deep eutectic solvent. The regenerated low-viscosity deep eutectic solvent can be recycled. Figure 5 In order to regenerate the leaching efficiency of the low-viscosity deep eutectic solvent, the ion leaching efficiency of the regenerated low-viscosity deep eutectic solvent is still above 95%.

[0052] (6) Recovery of lithium oxalate and nickel oxalate: The solid mixture of step (4) is dispersed with water, filtered to obtain an aqueous solution containing lithium oxalate and a paste-like salt layer of nickel oxalate, the paste-like salt layer of nickel oxalate is soaked in water and ethanol and ultrasonicated for 60 min, and nickel oxalate crystals are obtained by density differential centrifugation. The lithium oxalate aqueous solution is dehydrated to obtain lithium oxalate crystals.

[0053] (7) Regeneration of battery positive electrode materials: Lithium oxalate crystals, nickel oxalate crystals, solid cobalt oxalate and solid manganese oxalate were mixed and ball-milled according to the element ratio of Li: Ni: Co: Mn = 1: 0.5: 0.2: 0.3. The ball-milled powder was calcined at 800 °C for 12 h under aerobic conditions to obtain the regenerated positive electrode material R-NCM523.

[0054] (8) Electrochemical test of R-NCM523: R-NCM523 was made into electrode sheets and matched with lithium metal negative electrode to make button batteries, and the charge and discharge tests were carried out. The cycle performance is shown in Figure 6 .

[0055] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation, characterized in that: The following steps are involved: (1) A low viscosity deep eutectic solvent is prepared using 1-butyl-3-methylimidazolium chloride, oxalic acid and a diluent as raw materials; (2) Mixing the waste battery positive electrode material with a low-viscosity deep eutectic solvent and heating at 70-120 °C to obtain a mixed solution; (3) separating the mixed solution to obtain a leaching solution containing cobalt and manganese ions and a solid mixture containing lithium oxalate and nickel oxalate; (4) adding water to the solid mixture in step (3), dispersing the mixture, and separating the mixture to obtain an aqueous solution containing lithium oxalate and a paste-like salt layer of nickel oxalate; adding water to the leaching solution in step (3), allowing the mixture to precipitate naturally, and separating the solid cobalt oxalate, the solid manganese oxalate, and the clear solution; (5) Supplementing oxalic acid with the clear solution in step (4) and performing high-temperature dehydration to obtain a regenerated low-viscosity deep eutectic solvent; dehydrating the aqueous solution of lithium oxalate in step (4) to obtain lithium oxalate crystals; washing and purifying the paste salt layer nickel oxalate in step (4) to obtain nickel oxalate crystals; (6) The solid cobalt oxalate and solid manganese oxalate in step (4) and the lithium oxalate crystals and nickel oxalate crystals in step (5) are mixed in proportion and calcined to obtain a regenerated positive electrode material.

2. According to claim 1, a method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation, characterized in that: In step (1), the molar ratio of 1-butyl-3-methylimidazolium chloride to oxalic acid is 4:1 to 1:

1.

3. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (1), the diluent is propylene carbonate.

4. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (1), the amount of the diluent added is 10% to 30% of the total mass of the low-viscosity deep eutectic solvent, and the shear viscosity of the low-viscosity deep eutectic solvent is less than 40 Pa·s.

5. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (2), the mass ratio of the low viscosity deep eutectic solvent to the waste battery positive electrode material is 50:1~100:

1.

6. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (2), the heating time is 60 to 180 min.

7. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (4), in the precipitation of the leachate with water, the mass ratio of water to the leachate is 0.3:1 to 0.5:

1.

8. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1 is characterized in that: In step (5), the temperature of the high temperature dehydration is 80-100°C.

9. The method for recycling waste lithium battery positive electrode materials based on low-viscosity deep eutectic solvent double circulation according to claim 1, characterized in that: In step (6), the calcination temperature is 800-1000°C, the calcination time is 12-24 hours, and the calcination environment is aerobic conditions or air conditions.

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