Recycling method for optimizing cobalt in waste lithium battery

Abstract

The invention discloses a leaching method for optimizing cobalt in a waste lithium battery. Comprising the following steps: S1, discharging a recycled waste lithium battery, and drying, cooling, crushing and disassembling to obtain a first mixture after discharging; s2, the first mixture is subjected to alkaline leaching, and alkaline leaching residues are obtained; s3, the alkaline leaching residues are subjected to a reaction through sulfuric acid and a reducing agent, and first filtrate is obtained through filtering; s4, adjusting the pH value of the first filtrate, and removing impurities to obtain a second filtrate; and S5, carrying out cobalt precipitation treatment on the second filtrate. The sulfuric acid-reducing agent is adopted for cobalt precipitation, by-products are few, main components are almost not lost, and a good recycling effect is achieved. Meanwhile, a sulfuric acid-reducing agent mixed leaching system is adopted for acid leaching, the cobalt leaching effect is better, and generation of harmful gas in the reaction process is avoided.

Description

Technical Field

[0001] The invention relates to the field of lithium battery recycling, and in particular to a method for optimizing the recovery of cobalt in waste lithium batteries. Background Art

[0002] LiCoO 2 Lithium battery accounts for a large part of the market. With the continuous development of the new energy industry, how to recycle retired lithium battery positive electrode material batteries has become an imminent issue. As a rare element, cobalt has potential recycling value. It is divided into two categories according to the recycling results, recycling "elements" and recycling "materials". There are three main process routes for recycling waste lithium cobalt oxide positive electrode materials, hydrometallurgical process, pyrometallurgical process for extracting metal elements and direct regeneration of positive electrode materials. Hydrometallurgical treatment is to leach valuable metals from positive electrode materials and present them in ionic form in the solution, and then separate the metal ions to generate metal salts and other products. Therefore, the leaching effect of valuable metals from waste positive electrodes is very important.

[0003] The hydrometallurgical process disassembles and crushes waste lithium batteries into metals and powders. The powders are calcined, alkaline leached, and filtered to obtain filter mud, which is then acid-leached to obtain leachate. Finally, the leachate is extracted and recovered to obtain the corresponding valuable metals.

[0004] The recovery of cobalt generally adopts a mixed system of hydrochloric acid and hydrogen peroxide to leach the metallic cobalt in waste lithium-ion batteries. Although inorganic acid and hydrogen peroxide leaching have excellent leaching performance, there are currently two problems. One is that the side reaction products are numerous and harmful, such as the production of Cl 2 、NO X The cost of treating waste acid liquid is high. Another is that hydrogen peroxide is very easy to decompose, which poses a great safety hazard in actual production. The recycling efficiency is low, which causes secondary environmental pollution. It is necessary to further dispose of these harmful gases and waste liquids or develop more environmentally friendly ways to recycle them.

[0005] At the same time, the hydrochloric acid-hydrogen peroxide system is prone to corroding equipment, increasing production costs. In addition, the components of waste lithium batteries are complex, generally consisting of an outer shell and an internal battery core. The outer shell is usually stainless steel, nickel-plated metal or plastic, and the battery core is composed of a positive electrode, a negative electrode, a separator and an electrolyte. The recovered positive electrode material generally consists of about 90% lithium cobalt oxide active material, acetylene black conductive agent and organic adhesive. Waste lithium batteries contain multiple elements such as Co, Ni, Li, Al, Fe, Mn, Zn, Ca, etc., so it is necessary to design a method for recovering cobalt in waste lithium batteries according to actual production needs. Summary of the invention

[0006] The object of the present invention is to provide a method for leaching cobalt from waste lithium batteries with better cobalt ion leaching rate, less harmful byproducts and higher recycling efficiency.

[0007] To achieve the above object, the present invention proposes a method for optimizing the leaching of cobalt from waste lithium batteries, comprising the steps of:

[0008] S1, discharging the recycled waste lithium batteries, drying, cooling, crushing and disassembling them after discharging to obtain a first mixture;

[0009] S2, alkali leaching the first mixture to obtain alkali leaching residue;

[0010] S3, reacting the alkaline leaching residue with sulfuric acid and glucose, and filtering to obtain a first filtrate;

[0011] S4, adjusting the pH of the first filtrate to remove impurities to obtain a second filtrate;

[0012] S5, performing cobalt precipitation treatment on the second filtrate.

[0013] Furthermore, in step S2, the alkali is leached until the solution turns light yellow.

[0014] Furthermore, the alkali leaching time in step S2 is 25-40 minutes.

[0015] Furthermore, in step S2, the alkaline leaching is performed using sodium hydroxide or potassium hydroxide as the alkaline solution.

[0016] Furthermore, the solid-liquid ratio of sulfuric acid to alkaline leaching residue in step S3 is 1g:50-250ml.

[0017] Furthermore, in step S3, the ratio of sulfuric acid to glucose is 150-300 ml: 1-10 g. Too much glucose added will result in a lower leaching rate of cobalt ions in the first filtrate, which greatly reduces the recovery efficiency of cobalt in waste lithium batteries.

[0018] Furthermore, the concentration of sulfuric acid in step S3 is 1-4 mol / L. As the concentration of sulfuric acid increases, the content of cobalt ions in the first filtrate gradually tends to be stable, and further increasing the concentration of sulfuric acid will cause waste.

[0019] Furthermore, in step S4, the pH of the second filtrate is 4-6.

[0020] Furthermore, the cobalt precipitation treatment in step S4 is performed by adding a saturated ammonium oxalate solution into the second filtrate to precipitate cobalt.

[0021] In the present invention, the recycled waste lithium batteries are first subjected to discharge treatment, and then dried, cooled to room temperature, and crushed and disassembled to obtain a first mixture. The method for disassembling and discharging waste batteries is not limited to the method in the embodiment of the present invention, and other methods for discharging and disassembling waste lithium batteries can be applied.

[0022] The first mixture is dissolved by using NaOH or KOH solution, so that the aluminum foil in the first mixture is NaAlO 2 The alkali leaching residue is treated by sulfuric acid-glucose system to remove LiCoO in the waste lithium battery. 2 The layered structure of LiCoO is destroyed, making 2 Converted to CO 2+ , filter and adjust the pH value of the first filtrate to make Fe 2+ , Ca 2+ , Mn 2+ and a small amount of Al 3+ Impurities such as Co 2+ No precipitation. pH 5 can ensure the precipitation of impurity ions, and only a small part of cobalt is precipitated, with a cobalt loss of about 2%. Higher than pH 6 or lower than pH 5 will result in the inability to separate cobalt and impurity elements.

[0023] Compared with hydrochloric acid-hydrogen peroxide, which produces harmful Cl in the alkaline leaching process 2 , and the hydrochloric acid component in the treatment system is lost, so the system cannot be recycled. The use of sulfuric acid-glucose system to treat alkaline leaching residues in the present invention is conducive to the leaching and precipitation separation of cobalt in waste lithium batteries, with few by-products and almost no loss of main components, and has a good recycling effect. At the same time, the use of sulfuric acid-glucose system to treat alkaline leaching residues has a better effect of cobalt leaching and avoids the generation of harmful gases during the reaction process. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, and the examples of the embodiments are intended to be used to explain the present invention, and should not be construed as limiting the present invention. In the embodiments, if specific techniques or conditions are not indicated, the techniques or conditions described in the literature in this area or the product specifications are carried out. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained commercially. In the following embodiments, if not clearly stated, "%" refers to weight percentage.

[0025] The present invention proposes a method for optimizing the leaching of cobalt in waste lithium batteries, comprising the steps of:

[0026] S1, discharging the recycled waste lithium batteries, drying, cooling, crushing and disassembling them after discharging to obtain a first mixture;

[0027] S2, alkali leaching the first mixture to obtain alkali leaching residue;

[0028] S3, reacting the alkaline leaching residue with sulfuric acid and glucose, and filtering to obtain a first filtrate;

[0029] S4, adjusting the pH of the first filtrate to remove impurities to obtain a second filtrate;

[0030] S5, performing cobalt precipitation treatment on the second filtrate.

[0031] Co leaching rate (%) = Co content in the first filtrate / Co content in the first mixture * 100%

[0032] Co precipitation rate (%) = Cobalt precipitation amount in the second filtrate / Cobalt content in the first filtrate * 100%

[0033] Embodiment 1:

[0034] S1.1, soaking the recycled waste lithium batteries in a saturated NaCl solution for 24 hours for discharge treatment, drying the discharged waste lithium batteries in an oven at 80° C. for 12 hours, cooling to room temperature and crushing and disassembling to obtain a first mixture;

[0035] S1.2, reacting the first mixture with an excess of sodium hydroxide solution (10% by mass of NaOH, reacting for 30 min) until the solution turns light yellow, filtering, washing with water, and drying to obtain an alkaline leaching residue containing lithium cobalt oxide;

[0036] S1.3, weigh 2g of alkaline leaching residue, add 300ml of 2mol / l sulfuric acid solution and 5g of glucose, place in a 90℃ constant temperature water bath to react for one hour, filter to obtain the first filtrate, and determine the cobalt leaching rate in the first filtrate;

[0037] S1.4, adjusting the pH of the first filtrate to 5 with NaOH solution to precipitate and remove impurities to obtain a second filtrate;

[0038] S1.5. Adjust the pH of the second filtrate to 2, heat to 60°C, add 1.5 times the volume of a saturated solution of cobalt oxalate to precipitate cobalt, and determine the cobalt precipitation rate.

[0039] Table 1 shows the experimental results of the leaching rate and precipitation rate of cobalt in waste batteries in Example 1 of the present invention. The experiment was repeated three times to obtain the three results in Table 1. It can be found that the cobalt content in the waste lithium battery does not affect the recovery of the cobalt, and the recovery rate is higher than 96%. At the same time, it is proved that the recovery method of the present invention can better recover the cobalt in the waste batteries and reduce the waste of cobalt.

[0040] Table 1: Cobalt leaching rate and cobalt precipitation rate in different waste batteries in one embodiment of the present invention

[0041]

[0042]

[0043] Embodiment 2:

[0044] S2.1, soaking the recovered waste lithium batteries in a saturated NaCl solution for 24 hours for discharge treatment, drying the discharged waste lithium batteries in an oven at 80° C. for 12 hours, and cooling to room temperature to obtain a first mixture;

[0045] S2.2, reacting the first mixture with an excess potassium hydroxide solution (10% by mass KOH, reacting for 25 min) until the solution turns light yellow, filtering, washing with water, and drying to obtain an alkaline leaching residue containing lithium cobalt oxide;

[0046] S2.3, weigh 2g of alkaline leaching residue, add 300ml of 2mol / L sulfuric acid solution and glucose, place in a 90℃ constant temperature water bath to react for one hour, filter to obtain a first filtrate, and determine the cobalt leaching in the first filtrate;

[0047] S2.4, adjusting the pH of the first filtrate to 5 with NaOH solution to precipitate and remove impurities to obtain a second filtrate;

[0048] S2.5. Adjust the pH of the second filtrate to 2, heat to 60°C, add 1.5 times the volume of a saturated cobalt oxalate solution to precipitate cobalt, and determine the cobalt precipitation rate.

[0049] As shown in Table 2, by adjusting the amount of glucose added, it can be seen that the leaching rate of cobalt from waste batteries in the sulfuric acid system without adding glucose is only 44.14%, while adding 1, 5, and 10 g of glucose to the sulfuric acid-glucose system, respectively, greatly improves the leaching rate of cobalt in the alkaline leaching residue, and the leaching rates are all above 65%. The addition of glucose can greatly improve the leaching rate of cobalt in the alkaline leaching residue.

[0050] Table 2 Cobalt leaching rate and cobalt precipitation rate under acid leaching with different glucose addition amounts

[0051] Cobalt content in used batteries / % 45.23 45.23 45.23 45.23 Glucose addition amount / g 0 1 5 10 Leaching rate / % 44.14 65.43 96.57 74.31 Cobalt deposition rate / % 98.54 98.10 98.43 98.52

[0052] Embodiment 3:

[0053] S3.1, soaking the recovered waste lithium batteries in a saturated NaCl solution for 24 hours for discharge treatment, drying the discharged waste lithium batteries in an oven at 80° C. for 12 hours, and cooling to room temperature to obtain a first mixture;

[0054] S3.2, reacting the first mixture with an excess of sodium hydroxide solution (10% by mass of NaOH, reacting for 40 min) until the solution turns light yellow, filtering, washing with water, and drying to obtain an alkaline leaching residue containing lithium cobalt oxide;

[0055] S3.3, weigh 2 g of alkaline leaching residue, add 300 mL of sulfuric acid solution and 5 g of glucose, place in a 90°C constant temperature water bath to react for one hour, filter to obtain the first filtrate, and determine the cobalt leaching rate in the first filtrate;

[0056] S3.4, adjusting the pH of the first filtrate to 5 with NaOH solution to precipitate and remove impurities to obtain a second filtrate;

[0057] S3.5. Adjust the pH of the second filtrate to 2, heat to 60°C, add 1.5 times the volume of a saturated solution of cobalt oxalate to precipitate cobalt, and measure the cobalt precipitation rate.

[0058] As shown in Table 3, it can be seen that when the concentration of sulfuric acid in the leaching system is 0.1 mol / L, the leaching rate of cobalt in the alkaline leaching residue is only 42.30%. The leaching rate is too low, resulting in a large amount of cobalt in the waste battery that has not been recovered. When the sulfuric acid concentration is 1 mol / L, the leaching rate of cobalt in the alkaline leaching residue is significantly increased to 85.47%. When the sulfuric acid concentration is further increased to 2 mol / L or 3 mol / L, the leaching rate of cobalt shows a stable trend of 96.57% and 97.67% respectively. When the sulfuric acid concentration is 4 mol / L, the leaching rate is basically the same as when the sulfuric acid concentration is 3 mol / L. Therefore, when the sulfuric acid concentration is higher than 4 mol / L, the leaching rate of cobalt does not increase significantly. Considering the comprehensive cost and safety, the leaching rate of cobalt in the system is optimal when the sulfuric acid concentration is in the range of 1-4 mol / L.

[0059] Table 3 Cobalt leaching rate and cobalt precipitation rate under different sulfuric acid concentrations

[0060] Cobalt content in used batteries / % 45.23 45.23 45.23 45.23 45.23 Sulfuric acid concentration / mol / L 0.1 1.0 2.0 3.0 4.0 Leaching rate / % 42.30 85.47 96.57 97.67 97.64 Cobalt deposition rate / % 98.54 98.10 98.43 98.50 98.48

[0061] Embodiment 4:

[0062] S4.1, soaking the recovered waste lithium batteries in a saturated NaCl solution for 24 hours for discharge treatment, drying the discharged waste lithium batteries in an oven at 80° C. for 12 hours, and cooling to room temperature to obtain a first mixture;

[0063] S4.2, reacting the first mixture with an excess of sodium hydroxide solution (10% by mass of NaOH, reacting for 30 min) until the solution turns light yellow, filtering, washing with water, and drying to obtain an alkaline leaching residue containing lithium cobalt oxide;

[0064] S4.3, weigh 2g of alkaline leaching residue, add 300ml of 2mol / l sulfuric acid solution and 5g of glucose, place in a 90℃ constant temperature water bath to react for one hour, filter to obtain the first filtrate, and determine the cobalt leaching rate in the first filtrate;

[0065] S4.4, adjusting the pH of the first filtrate with a NaOH solution to precipitate and remove impurities to obtain a second filtrate;

[0066] S4.5. Adjust the pH of the second filtrate to 2, heat to 60°C, add 1.5 times the volume of a saturated cobalt oxalate solution to precipitate cobalt, and determine the cobalt precipitation rate.

[0067] Table 4 shows the existing pH values ​​for precipitating cobalt ions. When the pH is higher than 4, precipitation of impurity ions is guaranteed, and only a small part of cobalt is precipitated. When the pH is higher than 6, cobalt ions in the first filtrate will also precipitate. At the same time, it can be seen from Table 5 that when the pH exceeds 6, the cobalt precipitation rate drops sharply from 97.42% to 42.73%, resulting in a large loss of cobalt recovery. Therefore, the optimal pH range for impurity removal is 4-6.

[0068] Table 4 pH value of cobalt hydroxide precipitation

[0069] Metal hydroxide <![CDATA[K sp ]]> pH value at which precipitation begins pH value for complete precipitation <![CDATA[Co(OH) 2 ]]> <![CDATA[2.0×10 -16 ]]> 6.2 8.7

[0070] Table 5 Cobalt leaching rate and cobalt precipitation rate under different impurity removal pH adjustment

[0071] Cobalt content in used batteries / % 45.23 45.23 45.23 45.23 pH value of impurities removal 4 5 6 7 Leaching rate / % 96.45 96.57 96.83 96.54 Cobalt deposition rate / % 96.54 98.43 97.42 41.73

[0072] Embodiment 5:

[0073] S5.1, soaking the recovered waste lithium batteries in a saturated NaCl solution for 24 hours for discharge treatment, drying the discharged waste lithium batteries in an oven at 80° C. for 12 hours, and cooling to room temperature to obtain a first mixture;

[0074] S5.2, reacting the first mixture with an excess of sodium hydroxide solution (10% by mass of NaOH, reacting for 35 min) until the solution turns light yellow, filtering, washing with water, and drying to obtain an alkaline leaching residue containing lithium cobalt oxide;

[0075] S5.3, weigh 2g of alkaline leaching residue, add 2mol / l sulfuric acid solution and 5g of glucose, place in a 90°C constant temperature water bath for one hour, filter to obtain a first filtrate, and determine the cobalt leaching rate in the first filtrate;

[0076] S5.4, adjusting the pH of the first filtrate to 6 with NaOH solution to precipitate and remove impurities to obtain a second filtrate;

[0077] S5.5. The pH of the second filtrate was adjusted to 2, heated to 60° C., 1.5 times the volume of a saturated cobalt oxalate solution was added to precipitate cobalt, and the cobalt precipitation rate was measured. The recovery results are shown in Table 6.

[0078] By adjusting the ratio of sulfuric acid volume to alkaline leaching residue mass in the sulfuric acid-glucose system, the ratio of sulfuric acid to alkaline leaching residue is within the range of 50-250ml:1g, so that the leaching rate of cobalt is maintained above 70%. When the ratio of sulfuric acid to alkaline leaching residue is within the range of 100-200ml:1g, the leaching rate of cobalt is greater than 87%.

[0079] Table 6 Cobalt leaching rate and cobalt precipitation rate under different solid-liquid ratio acid leaching

[0080] Cobalt content in used batteries / % 45.23 45.23 45.23 45.23 45.23 Sulfuric acid volume / ml 100 200 300 400 500 Leaching rate / % 70.63 90.45 96.57 87.25 75.52 Cobalt deposition rate / % 96.27 96.72 98.43 97.92 98.41

[0081] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for optimizing the recovery of cobalt from waste lithium batteries, characterized in that: Includes steps: S1, discharging the recycled waste lithium batteries, drying, cooling, crushing and disassembling them after discharging to obtain a first mixture; S2, alkali leaching the first mixture to obtain alkali leaching residue; S3, reacting the alkaline leaching residue with sulfuric acid and glucose, and filtering to obtain a first filtrate; S4, adjusting the pH of the first filtrate to remove impurities to obtain a second filtrate; S5, performing cobalt precipitation treatment on the second filtrate.

2. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: In step S2, the alkali is used to leaching until the solution turns light yellow.

3. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The alkali leaching time in step S2 is 25-40 minutes.

4. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: In step S2, the alkali leaching uses sodium hydroxide or potassium hydroxide as the alkali solution.

5. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The solid-liquid ratio of sulfuric acid to alkali leaching residue in step S3 is 50-250 ml: 1 g.

6. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The ratio of sulfuric acid to glucose in step S3 is 150-300 ml: 1-10 g.

7. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The concentration of sulfuric acid in step S3 is 1-4 mol / L.

8. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The pH of the second filtrate in step S4 is 4-6.

9. The method for optimizing the recovery of cobalt in waste lithium batteries according to claim 1, characterized in that: The cobalt precipitation treatment in step S5 is performed by adding a saturated ammonium oxalate solution into the second filtrate to precipitate cobalt.

Images