A Method for Recycling Waste Lithium Battery Materials

Abstract

The present invention discloses a method for recycling waste lithium battery materials, comprising the following steps: S1. Acid leaching the battery black powder; S2. Adding iron powder to remove copper; S3. Adding an oxidizing agent; S4. Adding extractant A to extract calcium and zinc to obtain a raffinate; S5. Adding extractant P507 to the raffinate obtained in S4 to extract cobalt and nickel to obtain a raffinate containing manganese, magnesium, and lithium; S6. Adding extractant Cy-272 to the raffinate obtained in S5 to extract nickel and magnesium to obtain a raffinate containing lithium; S7. Adding liquid caustic soda to the raffinate obtained in S6, filtering under pressure, concentrating, crystallizing, and centrifuging to separate anhydrous sodium sulfate and centrifugal mother liquor; cooling and filtering the centrifugal mother liquor, adding soda ash to the filtrate to obtain crude lithium carbonate, washing with water, pulping, injecting carbon dioxide to generate a lithium bicarbonate solution, and finally forming lithium carbonate. The present invention can balance the recovery rate and recovery purity of metallic lithium. When the recovery rate reaches over 90%, the purity can reach over 98%.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and particularly relates to a method for recycling waste lithium battery materials. Background Art

[0002] Lithium batteries are a type of battery with a lithium metal or lithium alloy as the positive electrode material and a non-aqueous electrolyte solution. Due to their advantages such as high voltage, light weight, large specific energy, small self-discharge, long cycle life, no memory effect, wide working temperature range, and less environmental pollution, they have quickly occupied the secondary battery market and gradually replaced traditional rechargeable batteries. With the rapid development of mobile and portable devices, especially the rapid development of new energy vehicles in recent years, the application scope of lithium ion batteries has become more and more common, and the usage amount has increased year by year.

[0003] During the use of lithium batteries, when the battery capacity drops to 80% of the initial capacity, the battery reaches the end of its service life and will be scrapped. In order to reduce waste of resources, waste lithium batteries will be recycled. Lithium batteries are mainly composed of positive electrode materials, negative electrode materials, electrolytes, and separators. The precious metal resources in lithium batteries are mainly concentrated in the positive electrode materials. The positive electrode materials mainly contain metal resources such as cobalt, nickel, copper, and lithium. At present, the general recycling process for waste lithium battery positive electrode materials is to first perform mechanical treatment on the battery monomers, and then wet-process the positive electrode sheets to obtain valuable metals.

[0004] In the current recycling process, metal resources such as nickel, cobalt, and manganese are first extracted, and then lithium metal resources are finally extracted by carbonate precipitation. This process of finally extracting lithium inevitably causes the loss of lithium metal resources during the recycling process, and the recovery rate of lithium drops significantly. On the other hand, due to the large amount of lithium ions present in the leaching, extraction, and stripping processes, the purity of the nickel and cobalt salts obtained by extraction cannot reach the battery-grade standard and is difficult to be reused in the remanufacture of lithium ion batteries.

[0005] Therefore, many studies focus on preferentially extracting lithium. For example, a method for preferentially extracting metal lithium and simultaneously obtaining battery-grade metal salts from waste ternary lithium ion batteries disclosed in the applicant's previous invention patent CN113444885A, by roasting and reducing the waste battery black powder in a hydrogen atmosphere and then leaching with pure water, achieves the goal of preferentially extracting metal lithium resources and effectively improves the recovery rate of metal lithium.

[0006] However, due to the large number of metal elements in the positive electrode sheet and the mutual interference between different metal elements, the recovery purity of lithium is limited. Summary of the Invention

[0007] The object of the present invention is to provide a method for recycling waste lithium battery materials, which can balance the recovery rate and recovery purity of metallic lithium. When the recovery rate reaches over 90%, the purity can reach over 98%.

[0008] A method for recycling waste lithium battery materials provided by the present invention comprises the following steps:

[0009] S1. Add water to the battery black powder to form a slurry, add low-concentration sulfuric acid and a first reducing agent, adjust the pH to 1.0 - 2.5, control the temperature at 45°C to 55°C. After reacting for a period of time, add high-concentration sulfuric acid and a second reducing agent, control the reaction temperature above 80°C. After reacting for a period of time, obtain reaction liquid A. Press-filter reaction liquid A and collect filtrate A;

[0010] S2. Add iron powder to filtrate A obtained in S1, filter to remove copper in the filtrate, and obtain filtrate B;

[0011] S3. Add an oxidizing agent to filtrate B obtained in S2, heat to above 85°C, adjust the pH to 4.0 - 4.5, react to obtain reaction liquid B. Press-filter reaction liquid B and collect filtrate C;

[0012] S4. Add extractant A to filtrate C to extract calcium and zinc, and obtain a raffinate containing manganese, cobalt, nickel, magnesium, and lithium. The extractant A is a mixture of Cy-302 and P204, and the extraction conditions are pH 1.5 - 2.5 and temperature 25 - 35°C;

[0013] S5. Add extractant P507 to the raffinate obtained in S4 to extract cobalt and nickel, and obtain a raffinate containing manganese, magnesium, and lithium. The extraction conditions are: pH 2.0 - 3.5;

[0014] S6. Add extractant Cy-272 to the raffinate obtained in S5 to extract nickel and magnesium, and obtain a raffinate containing lithium. The extraction conditions are: pH 9.0 - 9.5 and extraction temperature 20 - 40°C;

[0015] S7. Add liquid caustic soda to the raffinate obtained in S6, maintain the pH at 9.0 - 10.0, press-filter to obtain filtrate D;

[0016] S8. Concentrate and crystallize filtrate D obtained in S7, and centrifuge to separate out anhydrous sodium sulfate and centrifuge mother liquor;

[0017] S9. Cool and filter the centrifuge mother liquor obtained in S8, add soda ash to the filtrate to obtain crude lithium carbonate;

[0018] S10. Wash and slurry the crude lithium carbonate obtained in S9, inject carbon dioxide to generate a lithium bicarbonate solution. Filter and separate the insoluble matter, and the purified lithium bicarbonate solution enters the pyrolysis process. After heating, lithium carbonate is formed.

[0019] Preferably, the first reducing agent is ascorbic acid and the second reducing agent is sodium thiosulfate.

[0020] Preferably, the addition amount of the second reducing agent is greater than that of the first reducing agent.

[0021] Preferably, in step S1, the concentration of the low-concentration sulfuric acid is 70% to 85%, and the concentration of the high-concentration sulfuric acid is 95% to 98%.

[0022] Preferably, in step S1, after the filter residue obtained by pressure filtration is slurried, sulfuric acid and a reducing agent are added, the pH is adjusted to 1.0 - 2.5, the reaction temperature is controlled to be higher than 80 °C to obtain reaction liquid A1, and the operations of S2 to S10 are performed on the reaction liquid A1.

[0023] Preferably, in step S4, the mass ratio of Cy-302 to P204 in the configuration is 3:1 - 1.5.

[0024] Preferably, in step S1, after adding the second reducing agent, the leaching temperature is controlled at 85 °C to 90 °C.

[0025] Preferably, in step S1, the reaction time for adding the first reducing agent is 0.5 h to 1.2 h.

[0026] Preferably, in step S1, the reaction time for adding the second reducing agent is 1 h to 1.5 h.

[0027] Preferably, the extractants Cy-302, P204, P507, and Cy-272 are saponified before use.

[0028] By implementing the above technical solutions, the present invention has the following beneficial effects:

[0029] 1. The present invention optimizes the separation process of ions, and recovers copper, (calcium, zinc), cobalt, nickel, magnesium, and lithium successively, which can reduce the mutual interference between metal ions and overcome the influence of mutual interference on the ion recovery rate and recovery purity.

[0030] 2. When leaching the battery slurry, the present invention uses two reducing agents added successively to reduce metal ions in stages. The first reducing agent has strong reducibility and can quickly reduce metal ions at a lower temperature. The second reducing agent has weak reducibility and can fully reduce metal ions at a higher temperature. The cooperation of the first reducing agent and the second reducing agent can significantly improve the leaching rate of metal ions.

[0031] 3. By optimizing the sulfuric acid concentration and reducing agent used in leaching, the present invention can give full play to the respective advantages of the two reducing agents and improve the leaching rate of metal ions.

[0032] 4. The present invention optimizes the extractant, especially extractant A for extracting calcium and zinc. By using a composite extractant and optimizing the extraction conditions, the relative specificity of extraction can be improved. With fewer extraction stages, high extraction rates can be achieved, the extraction efficiency can be increased, and the loss of other ions can be reduced. Specific Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] With the rapid development of new energy vehicles in recent years, the application scope of lithium-ion batteries has become more and more common, and the usage has increased year by year. Recycling used lithium-ion batteries is the most effective means to recycle used lithium-ion batteries.

[0035] The recycling of used lithium-ion batteries mainly includes two parts. The first part is completed in the dry process workshop, including sorting, discharging, disassembling and crushing of used lithium-ion battery raw materials; the second part is completed in the wet process workshop, including processes such as batching, leaching, and extraction.

[0036] The First Part

[0037] 1. Cascade utilization of used lithium-ion batteries

[0038] In the cascade utilization workshop of used lithium-ion battery raw materials, the batteries are sorted. The batteries that meet the requirements of cascade utilization after detection are recharged and sold externally, and the waste batteries that do not meet the requirements of cascade utilization enter the subsequent discharging process.

[0039] 2. Discharging

[0040] Before disassembling and separating used lithium-ion batteries, based on safety requirements, it is generally necessary to first perform a discharging pretreatment. A common method is to place the used lithium-ion batteries in a salt solution (such as Na2SO4 solution) for about a week.

[0041] 3. Disassembly, mechanical crushing and sorting

[0042] The discharged lithium-ion batteries enter the mechanical crushing process through a Z-shaped belt conveyor. The lithium-ion batteries are crushed by a multi-stage crushing device, and the crushing particle size is 5-10 mm. Then, the materials are screened into different particle sizes through a vibrating screen, and the materials with different particle sizes are respectively combined and sorted to separate the plastic and the battery shell, and the remaining materials enter the next process. The dust generated during the process is collected centrally and treated.

[0043] 4. Pyrolysis

[0044] The materials that have undergone mechanical crushing and sorting processes enter the pyrolysis furnace through a fully automatic feeding system for pyrolysis. After pyrolysis is completed, the materials enter the next process.

[0045] 5. Multi-stage sorting

[0046] After pyrolysis, due to the removal of the binder, the current collectors and the positive and negative electrode powders are more likely to fall off. The positive and negative mixed powders can be separated by vibration sorting, and copper and aluminum can be separated by specific gravity sorting to obtain battery black powder, which enters the wet process workshop for subsequent treatment.

[0047] The second part will be introduced in detail in the following embodiments.

[0048] Example 1

[0049] A method for recycling waste lithium battery materials includes the following steps:

[0050] S1. Add 2 kg of the battery black powder obtained from the first part to 7 L of water to form a slurry, add 15 mol of sulfuric acid with a mass concentration of 70% and 1 kg of ascorbic acid, adjust the pH to 2.0, control the temperature at 50 °C, after reacting for 1 h, add 15 mol of sulfuric acid with a mass concentration of 95% and 1.5 kg of sodium thiosulfate, control the reaction temperature at 85 °C, after reacting for 1.5 h, obtain reaction solution A, filter press reaction solution A, and collect filtrate A;

[0051] S2. Add iron powder to the filtrate A obtained in S1, filter to remove copper in the filtrate, and the copper element removal rate is about 94% to obtain filtrate B;

[0052] S3. Add hydrogen peroxide to the filtrate B obtained in S2 to oxidize Fe 2+ to Fe 3+ , heat to 90 °C, add soda ash to adjust the pH to 4.0, react to obtain reaction solution B. At this time, Fe 3+ and Al 3+ in the solution undergo hydrolysis and enter the slag. Filter press reaction solution B and collect filtrate C;

[0053] S4. Add extractant A saponified with 32% liquid caustic soda to filtrate C, perform 2-stage series countercurrent extraction on filtrate C to extract calcium and zinc, and obtain a raffinate containing manganese, cobalt, nickel, magnesium, and lithium. The extractant A is a mixture of Cy-302 and P204 (mass ratio 3:1), and the extraction conditions are pH 1.5 and temperature 25 °C; the organic phase is stripped with sulfuric acid with a concentration of 1 mol / L to obtain calcium and zinc solutions, realizing the recovery of calcium and zinc (recovery rate reaches 96%);

[0054] S5. Concentrate the raffinate obtained in S4, add the extractant P507 saponified with 32% liquid caustic soda, and perform two-stage countercurrent extraction on the raffinate to extract cobalt and nickel, obtaining a raffinate containing manganese, magnesium, and lithium. The extraction conditions are: pH 2.0; the organic phase is stripped with sulfuric acid at a concentration of 1 mol / L to obtain a cobalt and nickel solution, realizing the recovery of cobalt and nickel;

[0055] S6. Add the extractant Cy-272 saponified with 32% liquid caustic soda to the raffinate obtained in S5, and perform two-stage countercurrent extraction on the raffinate to extract nickel and magnesium, obtaining a raffinate containing lithium. The extraction conditions are: pH 9.0, extraction temperature 25°C; the organic phase is stripped with sulfuric acid at a concentration of 1 mol / L to obtain a cobalt and nickel solution, realizing the recovery of nickel and magnesium (the recovery rates of cobalt, nickel, and magnesium reach 95%);

[0056] S7. Add liquid caustic soda to the raffinate obtained in S6, maintain the pH at 9.0, and perform pressure filtration to obtain filtrate D;

[0057] S8. Concentrate and crystallize the filtrate D obtained in S7, and centrifugally separate anhydrous sodium sulfate and centrifugal mother liquor;

[0058] S9. Cool and filter the centrifugal mother liquor obtained in S8, and add soda ash to the filtrate to obtain crude lithium carbonate;

[0059] S10. Wash and pulp the crude lithium carbonate obtained in S9, inject carbon dioxide to form a lithium bicarbonate solution, filter and separate the insoluble matter, and the purified lithium bicarbonate solution enters the pyrolysis process. After heating, lithium carbonate is formed. The recovery rate of lithium reaches 92%, and the purity can reach 98.6%.

[0060] Example 2

[0061] A method for recycling waste lithium battery materials, comprising the following steps:

[0062] S1. Add 4 kg of the battery black powder obtained from the first part of the treatment to 15 L of water to form a slurry, add 15 mol of sulfuric acid with a mass concentration of 75% and 2 kg of ascorbic acid, adjust the pH to 2.0, control the temperature at 55°C, and after reacting for 1.5 h, add 15 mol of sulfuric acid with a mass concentration of 98% and 3 kg of sodium thiosulfate, control the reaction temperature at 90°C, and after reacting for 2 h, obtain reaction liquid A. Press-filter reaction liquid A and collect filtrate A;

[0063] S2. Add iron powder to the filtrate A obtained in S1, filter to remove copper in the filtrate, and the removal rate of copper element is about 96% to obtain filtrate B;

[0064] S3. Add hydrogen peroxide to the filtrate B obtained in S2, and the Fe in the solution2+ Oxidized to Fe 3+ , heated to 90 °C, added soda ash to adjust the pH to 4.2, and reacted to obtain reaction solution B. At this time, Fe 3+ and Al 3+ hydrolyzed and entered the slag. The reaction solution B was pressure-filtered, and the filtrate C was collected;

[0065] S4. Add extractant A to the filtrate C, and perform 2-stage series countercurrent extraction on the solution to extract calcium and zinc, obtaining a raffinate containing manganese, cobalt, nickel, magnesium, and lithium. The extractant A is a mixture of Cy-302 and P204 (mass ratio 3:1.5). The extraction conditions are pH 2.0 and temperature 25 °C; the organic phase is stripped with sulfuric acid with a concentration of 1 mol / L to obtain a calcium and zinc solution, realizing the recovery of calcium and zinc (recovery rate reaching 96%);

[0066] S5. Concentrate the raffinate obtained in S4, add extractant P507, and perform 3-stage series countercurrent extraction on the raffinate to extract cobalt and nickel, obtaining a raffinate containing manganese, magnesium, and lithium. The extraction conditions are: pH 2.0; the organic phase is stripped with sulfuric acid with a concentration of 1 mol / L to obtain a cobalt and nickel solution, realizing the recovery of cobalt and nickel;

[0067] S6. Add extractant Cy-272 to the raffinate obtained in S5, and perform 3-stage series countercurrent extraction on the raffinate to extract nickel and magnesium, obtaining a raffinate containing lithium. The extraction conditions are: pH 9.0, extraction temperature 25 °C; the organic phase is stripped with sulfuric acid with a concentration of 1 mol / L to obtain a cobalt and nickel solution, realizing the recovery of nickel and magnesium (recovery rate of cobalt, nickel, and magnesium reaching 94%);

[0068] S7. Add liquid caustic to the raffinate obtained in S6, maintain the pH to 9.0, and perform pressure filtration to obtain filtrate D;

[0069] S8. Concentrate and crystallize the filtrate D obtained in S7, and centrifugally separate anhydrous sodium sulfate and centrifugal mother liquor;

[0070] S9. Cool and filter the centrifugal mother liquor obtained in S8, and add soda ash to the filtrate to obtain crude lithium carbonate;

[0071] S10. Wash and pulp the crude lithium carbonate obtained in S9, inject carbon dioxide to generate a lithium bicarbonate solution. The insoluble matter is filtered and separated, and the purified lithium bicarbonate solution enters the pyrolysis process. After heating, lithium carbonate is formed. The recovery rate of lithium reaches 93%, and the purity can reach 98.2%.

[0072] Example 3

[0073] Different from Example 1, in this example, in step S1, after pressure filtration of the filter residue, after pulping, 98% sulfuric acid and reducing agent sodium thiosulfate are added, the pH is adjusted to 15, the reaction temperature is controlled at 90 °C to obtain reaction liquid A1, and reaction liquid A1 is mixed with reaction liquid A, and operations of S2 to S10 are carried out.

[0074] The lithium recovery rate obtained reaches 93%, and the purity can reach 98.4%.

[0075] Example 4

[0076] Different from Example 1, in step S4, the extractant A is a mixture of Cy-302, P204 and ethylene oxide (mass ratio 3:1:0.1). The lithium recovery rate finally obtained reaches 95%, and the purity can reach 99.2%.

[0077] Comparative Example 1:

[0078] Different from Example 1, the operation of step S1 is different. In this comparative example S1, 2 kg of the battery black powder obtained from the first part is added with 7 L of water to form a slurry, 30 mol of sulfuric acid with a mass concentration of 95% and 2.5 kg of sodium thiosulfate are added, the reaction temperature is controlled at 85 °C, after reacting for 1.5 h, reaction liquid A is obtained, reaction liquid A is pressure-filtered, and filtrate A is collected.

[0079] The lithium recovery rate finally obtained reaches 90%, and the purity can reach 97.1%.

[0080] Comparative Example 2:

[0081] Different from Example 1, in this comparative example S1, both the first reducing agent and the second reducing agent are sodium thiosulfate.

[0082] The lithium recovery rate finally obtained reaches 82%, and the purity can reach 97.2%.

[0083] Comparative Example 3:

[0084] Different from Example 1, in this comparative example S1, both the first reducing agent and the second reducing agent are ascorbic acid.

[0085] The lithium recovery rate finally obtained reaches 78%, and the purity can reach 97.2%.

[0086] Comparative Example 4:

[0087] It is different from Example 1 in that in S1, 2 kg of the battery black powder obtained from the first part is added with 7 L of water to form a slurry, 15 mol of sulfuric acid with a mass concentration of 95% and 1 kg of ascorbic acid are added, the pH is adjusted to 2.0, the temperature is controlled at 85°C, after reacting for 1 h, 15 mol of sulfuric acid with a mass concentration of 95% and 1.5 kg of sodium thiosulfate are added, the reaction temperature is controlled at 85°C, after reacting for 1.5 h, a reaction solution A is obtained, and the reaction solution A is pressure-filtered to collect the filtrate A.

[0088] The lithium recovery rate finally obtained reaches 75%, and the purity can reach 96.6%.

[0089] Comparative Example 5:

[0090] It is different from Example 1 in that in step S4, the extractant A is Cy-302. The lithium recovery rate reaches 88%, and the purity can reach 92.4%.

[0091] Comparative Example 6:

[0092] It is different from Example 1 in that in step S4, the extractant A is P204. The lithium recovery rate reaches 86%, and the purity can reach 90.1%.

[0093] Comparative Example 7:

[0094] It is different from Example 1 in that in step S4, the extractant A is a mixture of Cy-302 and P204 (mass ratio 1:3), and the lithium recovery rate reaches 82%, and the purity can reach 91.4%.

Claims

1. A method for recycling waste lithium battery materials, characterized in that, It includes the following steps: S1. Add water to the battery black powder to form a slurry, add low-concentration sulfuric acid and a first reducing agent, adjust the pH to 1.0 - 2.5, control the temperature at 45°C to 55°C. After reacting for a period of time, add high-concentration sulfuric acid and a second reducing agent, control the reaction temperature above 80°C. After reacting for a period of time, obtain reaction solution A. Filter press reaction solution A and collect filtrate A; the first reducing agent is ascorbic acid, and the second reducing agent is sodium thiosulfate; S2. Add iron powder to filtrate A obtained in S1, filter to remove copper in the filtrate, and obtain filtrate B; S3. Add an oxidizing agent to filtrate B obtained in S2, heat to above 85°C, adjust the pH to 4.0 - 4.5, react to obtain reaction solution B, filter press reaction solution B and collect filtrate C; S4. Add extractant A to filtrate C to extract calcium and zinc, and obtain a raffinate containing manganese, cobalt, nickel, magnesium, and lithium. The extractant A is a mixture of Cy-302 and P204. The extraction conditions are pH 1.5 - 2.5 and temperature 25 - 35°C; in step S4, the mass ratio of Cy-302 to P204 is 3:1 - 1.5; S5. Add extractant P507 to the raffinate obtained in S4 to extract cobalt and nickel, and obtain a raffinate containing manganese, magnesium, and lithium. The extraction conditions are: pH 2.0 - 3.5; S6. Add extractant Cy-272 to the raffinate obtained in S5 to extract nickel and magnesium, and obtain a raffinate containing lithium. The extraction conditions are: pH 9.0 - 9.5, extraction temperature 20 - 40°C; S7. Add liquid caustic to the raffinate obtained in S6, maintain the pH at 9.0 - 10.0, filter press to obtain filtrate D; S8. Concentrate and crystallize filtrate D obtained in S7, and centrifuge to separate anhydrous sodium sulfate and centrifuge mother liquor; S9. Cool and filter the centrifuge mother liquor obtained in S8, add soda ash to the filtrate to obtain crude lithium carbonate; S10. Wash and pulp the crude lithium carbonate obtained in S9, inject carbon dioxide to generate a lithium bicarbonate solution. Filter and separate the insoluble matter, and the purified lithium bicarbonate solution enters the pyrolysis process and forms lithium carbonate after heating.

2. The recycling method of waste lithium battery materials according to claim 1, characterized in that The addition amount of the second reducing agent is greater than that of the first reducing agent.

3. The recycling method of waste lithium battery materials according to claim 1, wherein In step S1, the concentration of the low-concentration sulfuric acid is 70% to 85%, and the concentration of the high-concentration sulfuric acid is 95% to 98%.

4. A method for recycling waste lithium battery materials according to claim 1, characterized in that, In step S1, for the filter residue after filter pressing, after pulping, add sulfuric acid and a reducing agent, adjust the pH to 1.0 - 2.5, control the reaction temperature above 80°C to obtain reaction solution A1, and perform operations from S2 to S10 on reaction solution A1.

5. A method for recycling waste lithium battery materials according to claim 1, characterized in that, In step S1, after adding the second reducing agent, the leaching temperature is controlled at 85°C to 90°C.

6. The recycling method of a waste lithium battery material according to claim 1, characterized in that, In step S1, the reaction time for adding the first reducing agent is 0.5h to 1.2h.

7. A method for recycling waste lithium battery materials according to claim 1, characterized in that, In step S1, the reaction time for adding the second reducing agent is 1h to 1.5h.

8. A method for recycling waste lithium battery materials according to claim 1, characterized in that, The extractants Cy-302, P204, P507, and Cy-272 are saponified before use.