A method for recycling fluorine in the process of recycling retired lithium batteries

Abstract

The present application discloses a method for the resource utilization of fluorine during the recycling of retired lithium batteries, belonging to the technical field of lithium battery recycling; the method provided by the present application is to mix the defluorination residue in the process of recycling retired lithium batteries with liquid A, a first inorganic acid, and sodium silicate, and then heat and react. After the reaction ends, solid-liquid separation is carried out to obtain a first-stage leaching residue and a first-stage leaching solution. Subsequently, the first-stage leaching residue is mixed with water, a second inorganic acid, and sodium silicate, and then heated and reacted. After the reaction ends, solid-liquid separation is carried out to obtain a second-stage leaching residue and a second-stage leaching solution. Finally, the second-stage leaching residue is mixed with a soda ash solution for reaction. After the reaction ends, solid-liquid separation is carried out to obtain sodium fluoride. The method provided by the present application can realize the resource utilization of fluorine; specifically, the recovery rate of fluorine in the defluorination residue is above 90%, and the purity of the obtained sodium fluoride is above 70%; moreover, the method provided by the present application is simple to operate and suitable for practical application.

Description

Technical Field

[0001] This application belongs to the technical field of lithium battery recycling, and particularly relates to a method for fluorine resource utilization in the recycling process of retired lithium batteries. Background Art

[0002] With the increasing proximity of the carbon neutrality goal, the new energy market is booming with boundless prospects. Lithium-ion batteries are currently at the forefront of the energy market. However, the lifespan of lithium-ion batteries is only 3 - 5 years. As more and more lithium batteries enter the end-of-life stage, reasonably and effectively treating retired batteries has become an inevitable requirement for environmental protection and sustainable resource development.

[0003] When recovering valuable metals from retired lithium batteries, a hydrometallurgical process is generally used. The hydrometallurgical process is a relatively mature and widely used process for recycling waste lithium-ion batteries. Generally, retired lithium batteries go through processes such as discharging, crushing, screening, acid leaching, impurity removal, and extraction to recover nickel, cobalt, manganese, and lithium. Since the fluorine element in the electrolyte and binder will be present throughout the recycling process, and a large amount of calcium chloride, magnesium chloride, etc. will be consumed during the entire lithium recovery process, the existing fluorine element will not only corrode the production equipment but also be introduced into the lithium product, resulting in unqualified products. Therefore, defluorination is required. However, a large amount of fluorine-containing waste residue, such as calcium fluoride and magnesium fluoride, will be generated during the defluorination process. For the large amount of fluorine-containing waste residue, i.e., defluorination residue, generated during the defluorination process, there is currently no effective recycling method, leading to a waste of fluorine resources. Summary of the Invention

[0004] The purpose of this application is to overcome the deficiencies of the above-mentioned existing technologies and provide a method for fluorine resource utilization in the recycling process of retired lithium batteries that can effectively recover fluorine from the defluorination residue and improve the fluorine recovery rate.

[0005] To achieve the above purpose, the technical solution adopted in this application is: A method for fluorine resource utilization in the recycling process of retired lithium batteries, comprising the following steps:

[0006] (1) Mix the defluorination residue in the recycling process of retired lithium batteries with liquid A, a first inorganic acid, and sodium silicate, and then heat and react. After the reaction ends, perform solid-liquid separation to obtain a first-stage leaching residue and a first-stage leaching solution;

[0007] (2) Mix the first-stage leaching residue with water, a second inorganic acid, and sodium silicate, and then heat and react. After the reaction ends, perform solid-liquid separation to obtain a second-stage leaching residue and a second-stage leaching solution;

[0008] (3) Mix the second-stage leaching residue with a soda ash solution and react. After the reaction ends, perform solid-liquid separation to obtain sodium fluoride;

[0009] The liquid A is water or the second-stage leaching solution.

[0010] In the method for fluorine resource utilization during the recycling of retired lithium batteries provided by this application, a two-stage acid leaching process is utilized. In each stage, an acid + sodium silicate process is adopted for acid dissolution treatment, so that fluorine in the defluorination residue can be transformed into crude sodium fluorosilicate to the greatest extent, and further the crude sodium fluorosilicate is made into sodium fluoride, thereby realizing the resource utilization of fluorine. In addition, the inventor's research found that the liquid A in step (1) can be water or the second-stage leaching solution. When using the second-stage leaching solution, not only the same effect as water can be achieved, but also the recycling of the second-stage leaching solution can be realized.

[0011] As a preferred implementation manner of the method for fluorine resource utilization during the recycling of retired lithium batteries described in this application, before step (1) of this application, the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the defluorination residue during the recycling of retired lithium batteries are measured by atomic absorption spectrophotometry. At the same time, after steps (2) and (3), the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the first-stage leaching solution, the first-stage leaching residue, the second-stage leaching solution, and the second-stage leaching residue are measured by atomic absorption spectrophotometry respectively.

[0012] As a preferred implementation manner of the method for fluorine resource utilization during the recycling of retired lithium batteries described in this application, in step (1), the ratio of the sum of the molar amounts of calcium and magnesium elements in the defluorination residue to the molar amount of H + in the first inorganic acid is (0.4 - 0.8):1, the ratio of the sum of the molar amounts of nickel, cobalt, and manganese in the defluorination residue to the molar amount of H + in the first inorganic acid is (0.06 - 0.15):1, the ratio of the molar amount of sodium silicate to the molar amount of H + in the first inorganic acid is (0.1 - 0.7):1, and the liquid-solid ratio of the liquid A to the defluorination residue is (1.5 - 3) mL:1 g.

[0013] As a preferred implementation manner of the method for fluorine resource utilization during the recycling of retired lithium batteries described in this application, in step (1), the temperature of the heating reaction is 60 - 150 °C, and the time is 1 - 4 h.

[0014] The inventor's research found that when using the above-mentioned molar ratios, reaction temperature, and time in the first-stage leaching, fluorine can be transformed into sodium fluorosilicate to the greatest extent and exist in the form of the first-stage leaching residue.

[0015] As a preferred implementation manner of the method for fluorine resource utilization during the recycling of retired lithium batteries described in this application, in step (2), the ratio of the sum of the molar amounts of calcium and magnesium elements in the first-stage leaching residue to the molar amount of H + in the second inorganic acid is (0.2 - 0.7):1, and the ratio of the molar amount of sodium silicate to the molar amount of H +The molar ratio is (0.1 - 0.3) : 1, and the liquid-solid ratio of water to the first-stage leaching residue is (1 - 5) mL : 1 g.

[0016] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, in step (2), the temperature of the heating reaction is 60 - 150 °C, and the time is 3 - 6 h.

[0017] The inventors have found through research that when using the above-mentioned molar ratio of substances, reaction temperature, and time in the second-stage leaching, fluorine can be converted into sodium fluorosilicate to the greatest extent and exist in the form of the second-stage leaching residue.

[0018] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, in step (3), the molar amount of F + in the second-stage leaching residue and the molar amount of soda ash are in a ratio of 1 : (0.4 - 1.2).

[0019] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, in step (3), the concentration of soda ash is 150 - 300 g / L.

[0020] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, in step (3), the reaction temperature is 60 - 100 °C, and the time is 1 - 5 h.

[0021] The inventors have found through research that when using the soda ash solution within the above-mentioned concentration range, reaction temperature, and time in step (3), the purity of the subsequent obtained sodium fluoride can be ensured within an acceptable range. Specifically, the purity of the obtained sodium fluoride is above 70%; thus, unnecessary processes for further purifying sodium fluoride can be avoided.

[0022] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, the first inorganic acid and the second inorganic acid are each independently selected from any one of hydrochloric acid, nitric acid, and carbonic acid.

[0023] Preferably, both the first inorganic acid and the second inorganic acid are selected from hydrochloric acid.

[0024] As a preferred embodiment of the method for fluorine resource utilization in the recycling process of waste lithium batteries described in this application, the solid-liquid separation is carried out by pressure filtration.

[0025] Compared with the prior art, the beneficial effects of this application are:

[0026] The method for the resource utilization of fluorine in the recycling process of retired lithium batteries provided by this application can convert the fluorine in the defluorinated slag into crude sodium fluorosilicate to the greatest extent by using a two-stage acid leaching process, and in each stage, an acid + sodium silicate process is used for acid dissolution treatment. Further, the crude sodium fluorosilicate is made into sodium fluoride, thereby realizing the resource utilization of fluorine. Specifically, the recovery rate of fluorine in the defluorinated slag is above 90%, and the purity of the obtained sodium fluoride is above 70%. Moreover, the method provided by this application is simple to operate and suitable for practical applications. Description of the Drawings

[0027] Figure 1 It is a schematic flow chart of the method for the resource utilization of fluorine in the recycling process of retired lithium batteries in Example 1. Detailed Embodiments

[0028] To better illustrate the purpose, technical solution and advantages of this application, the following will further illustrate this application with specific embodiments.

[0029] The reagents, methods and equipment used in this application are all conventional reagents, methods and equipment in this field unless otherwise specified.

[0030] Example 1

[0031] The embodiment of this application provides a method for the resource utilization of fluorine in the recycling process of retired lithium batteries. The schematic diagram of the method is as Figure 1 shown, and it includes the following steps:

[0032] (1) Take 1000 g of defluorinated slag in the recycling process of a certain retired lithium battery, detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese and sodium elements by atomic absorption spectrophotometry, then place it in a reaction tank, add 1800 mL of water, 171 g of sodium silicate and 1060 mL of hydrochloric acid with a mass fraction of 30% and mix evenly. Then heat it to 85 °C and react for 2 h. After the reaction ends, cool it down to 25 °C, and then carry out solid-liquid separation by pressure filtration to obtain 470 g of first-stage leaching residue and 2.8 L of first-stage leaching solution;

[0033] (2) Detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese and sodium elements in the first-stage leaching residue obtained in step (1) by atomic absorption spectrophotometry. Mix 470 g of the first-stage leaching residue with 1800 mL of water, 41 g of sodium silicate and 200 mL of hydrochloric acid with a mass fraction of 30% evenly, then heat it to 85 °C and react for 4 h. After the reaction ends, cool it down to 25 °C, and then carry out solid-liquid separation by pressure filtration to obtain 394 g of second-stage leaching residue and 1.9 L of second-stage leaching solution;

[0034] (3) Place 394 g of the secondary leaching residue from step (2) in a reaction tank, add 3.64 L of a soda ash solution with a mass concentration of 300 g / L, react at 85 °C for 2 h, cool down to 25 °C after the reaction, and then perform solid-liquid separation by pressure filtration to obtain sodium fluoride;

[0035] During the process of fluorine resource utilization in the recycling of retired lithium batteries, the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the defluorination residue, primary leaching residue, primary leachate, secondary leaching residue, and secondary leachate were detected by atomic absorption spectrophotometry, as shown in Table 1. The unit of the residue is %, and the unit of the liquid is g / L.

[0036] Table 1

[0037]

[0038]

[0039] Example 2

[0040] The embodiment of the present application provides a method for fluorine resource utilization in the recycling of retired lithium batteries, including the following steps:

[0041] (1) Take 1000 g of the defluorination residue in the recycling of a certain retired lithium battery, detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements by atomic absorption spectrophotometry, then place it in a reaction tank and add 1800 mL of water, 214 g of sodium silicate, and 1060 mL of hydrochloric acid with a mass fraction of 30% and mix evenly. Then heat to 145 °C and react for 1 h. After the reaction, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 465 g of primary leaching residue and 2.8 L of primary leachate;

[0042] (2) Detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the primary leaching residue obtained in step (1) by atomic absorption spectrophotometry. Mix 465 g of the primary leaching residue with 1800 mL of water, 40 g of sodium silicate, and 200 mL of hydrochloric acid with a mass fraction of 30% evenly, then heat to 145 °C and react for 3 h. After the reaction, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 401 g of secondary leaching residue and 1.9 L of secondary leachate;

[0043] (3) Place 401 g of the secondary leaching residue from step (2) in a reaction tank, add 3.64 L of a soda ash solution with a mass concentration of 300 g / L, react at 95 °C for 1 h, cool down to 25 °C after the reaction, and then perform solid-liquid separation by pressure filtration to obtain sodium fluoride;

[0044] During the process of fluorine resource utilization in the recycling of retired lithium batteries, the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in defluorinated slag, first-stage leaching slag, first-stage leaching solution, second-stage leaching slag, and second-stage leaching solution were detected by atomic absorption spectrophotometry, as shown in Table 2, where the unit of slag is %, and the unit of liquid is g / L.

[0045] Table 2

[0046]

[0047]

[0048] Example 3

[0049] An embodiment of the present application provides a method for fluorine resource utilization in the recycling of retired lithium batteries, including the following steps:

[0050] (1) Take 1000 g of defluorinated slag in the recycling of a certain retired lithium battery, detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements by atomic absorption spectrophotometry, then place it in a reaction tank, add 1800 mL of water, 1082 g of sodium silicate, and 1770 mL of hydrochloric acid with a mass fraction of 30%, mix evenly, then heat to 60 °C and react for 4 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 439 g of first-stage leaching slag and 3.5 L of first-stage leaching solution;

[0051] (2) Detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the first-stage leaching slag obtained in step (1) by atomic absorption spectrophotometry. Mix 439 g of first-stage leaching slag with 1800 mL of water, 72.3 g of sodium silicate, and 311 mL of hydrochloric acid with a mass fraction of 30% evenly, then heat to 60 °C and react for 6 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 372 g of second-stage leaching slag and 2.0 L of second-stage leaching solution;

[0052] (3) Place 372 g of the second-stage leaching slag obtained in step (2) in a reaction tank, add 3.89 L of soda ash solution with a mass concentration of 300 g / L, react at 80 °C for 5 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain sodium fluoride;

[0053] During the process of fluorine resource utilization in the recycling of retired lithium batteries, the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in defluorinated slag, first-stage leaching slag, first-stage leaching solution, second-stage leaching slag, and second-stage leaching solution were detected by atomic absorption spectrophotometry, as shown in Table 3, where the unit of slag is %, and the unit of liquid is g / L.

[0054] Table 3

[0055]

[0056] Example 4

[0057] An embodiment of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries, including the following steps:

[0058] (1) Take 1000 g of defluorinated slag in the process of recycling a certain retired lithium battery, and use atomic absorption spectrophotometry to detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements. Then place it in a reaction tank and add 1800 mL of water, 362 g of sodium silicate, and 1515 mL of hydrochloric acid with a mass fraction of 30% and mix evenly. Then heat to 110 °C and react for 1.5 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 425 g of primary leaching residue and 3.2 L of primary leaching solution;

[0059] (2) Use atomic absorption spectrophotometry to detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the primary leaching residue obtained in step (1). Mix 425 g of the primary leaching residue with 1800 mL of water, 67 g of sodium silicate, and 312 mL of hydrochloric acid with a mass fraction of 30% evenly and heat to 110 °C and react for 3.5 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 380 g of secondary leaching residue and 2.1 L of secondary leaching solution;

[0060] (3) Place 380 g of the secondary leaching residue in step (2) in a reaction tank, add 7.86 L of a soda ash solution with a mass concentration of 150 g / L, react at 85 °C for 2 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain sodium fluoride;

[0061] During the process of fluorine resource utilization in the recycling of retired lithium batteries, atomic absorption spectrophotometry is used to detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements in the defluorinated slag, primary leaching residue, primary leaching solution, secondary leaching residue, and secondary leaching solution as shown in Table 4, where the unit of the slag is %, and the unit of the liquid is g / L.

[0062] Table 4

[0063]

[0064] Example 5

[0065] An embodiment of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries. The only difference from Example 1 is that the addition amount of sodium silicate in step (1) is 135 g; the test data in the process of the method are shown in Table 5;

[0066] Table 5

[0067]

[0068] Example 6

[0069] The embodiment of the present application provides a method for fluorine resource utilization in the recycling process of retired lithium batteries. The only difference from Example 1 is that the addition amount of sodium silicate in step (2) is 20 g; the test data during the method process are shown in Table 6;

[0070] Table 6

[0071]

[0072] Example 7

[0073] The embodiment of the present application provides a method for fluorine resource utilization in the recycling process of retired lithium batteries. The only difference from Example 1 is that the reaction temperature in step (1) is 140 °C for 1 h; the test data during the method process are shown in Table 7;

[0074] Table 7

[0075]

[0076] Example 8

[0077] The embodiment of the present application provides a method for fluorine resource utilization in the recycling process of retired lithium batteries. The only difference from Example 1 is that the reaction temperature in step (2) is 60 °C for 5 h; the test data during the method process are shown in Table 8;

[0078] Table 8

[0079]

[0080] Comparative Example 1

[0081] The comparative example of the present application provides a method for fluorine resource utilization in the recycling process of retired lithium batteries. The difference from Example 1 is that one-stage leaching is adopted, including the following steps:

[0082] (1) Take 1000 g of defluorinated slag in the recycling process of a certain retired lithium battery, detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese, and sodium elements by atomic absorption spectrophotometry, then place it in a reaction tank, add 1800 mL of water, 171 g of sodium silicate, and 1060 mL of hydrochloric acid with a mass fraction of 30% and mix evenly, then heat to 85 °C and react for 2 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain 950 g of one-stage leaching residue and 2.8 L of one-stage leaching solution;

[0083] (2) Place 950 g of the one-stage leaching residue in step (1) in a reaction tank, add 3.64 L of a sodium carbonate solution with a mass concentration of 300 g / L, react at 85 °C for 2 h. After the reaction is completed, cool down to 25 °C, and then perform solid-liquid separation by pressure filtration to obtain sodium fluoride;

[0084] In the process of fluorine resource utilization during the recycling of retired lithium batteries, atomic absorption spectrophotometry was used to detect the contents of calcium, magnesium, fluorine, nickel, cobalt, manganese and sodium in the defluorination slag, the first-stage leaching slag and the first-stage leaching liquid as shown in Table 9, where the unit for the slag is %, and the unit for the liquid is g / L.

[0085] Table 9

[0086]

[0087] Comparative Example 2

[0088] The comparative example of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries. The difference from Example 1 is that the reaction temperature in step (3) is 50°C.

[0089] Comparative Example 3

[0090] The comparative example of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries. The only difference from Example 1 is that 480 mL of hydrochloric acid with a mass fraction of 30% is added in step (1); the test data during the method are shown in Table 10;

[0091] Table 10

[0092]

[0093] Comparative Example 4

[0094] The comparative example of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries. The only difference from Example 1 is that 80g of sodium silicate is added in step (1). The test data during the method are shown in Table 11.

[0095] Table 11

[0096]

[0097] Comparative Example 5

[0098] The comparative example of the present application provides a method for fluorine resource utilization in the process of recycling retired lithium batteries. The only difference from Example 1 is that 100 mL of hydrochloric acid with a mass fraction of 30% is added in step (2); the test data during the method are shown in Table 12;

[0099] Table 12

[0100]

[0101] Comparative Example 6

[0102] The comparative example of this application provides a method for the resource utilization of fluorine during the recycling of retired lithium batteries. The only difference from Example 1 is that 18 g of sodium silicate is added in step (1); the test data during the method process are shown in Table 13;

[0103] Table 13

[0104]

[0105] Comparative Example 7

[0106] The comparative example of this application provides a method for the resource utilization of fluorine during the recycling of retired lithium batteries. The only difference from Example 1 is that the reaction temperature is 180 °C for 2 h in step (1); the test data during the method process are shown in Table 14;

[0107] Table 14

[0108]

[0109] Comparative Example 8

[0110] The comparative example of this application provides a method for the resource utilization of fluorine during the recycling of retired lithium batteries. The only difference from Example 1 is that the reaction temperature is 40 °C for 6 h in step (2); the test data during the method process are shown in Table 15;

[0111] Table 15

[0112]

[0113] Effect Example

[0114] The effect example of this application verifies the recovery utilization rate of fluorine elements in the defluorination slag and the overall recovery utilization rate of fluorine elements during the leaching process in Examples 1-8 and Comparative Examples 2-8. Among them, the recovery utilization rate of fluorine elements in the defluorination slag during the leaching process is represented by y1, and the overall recovery rate of the process is represented by y2; y1 = (m 二段浸出渣 × Percentage content of fluorine elements in the secondary leaching slag) / (m 除氟渣 × Percentage content of fluorine elements in the defluorination slag) × 100%, y2 = (m 氟化钠 × Purity of sodium fluoride × 19 / 42) / (m 除氟渣 × Percentage content of fluorine elements in the defluorination slag) × 100%; In Comparative Example 1, y1 = (m 一段浸出渣 × Percentage content of fluorine elements in the primary leaching slag) / (m 除氟渣 × Percentage content of fluorine elements in the defluorination slag) × 100%, y2 = (m 氟化钠 × Purity of sodium fluoride × 19 / 42) / (m 除氟渣 × Percentage content of fluorine elements in the defluorination slag) × 100%;

[0115] Table 16

[0116]

[0117]

[0118] Note: In Comparative Examples 3 and 5, due to insufficient acid, most of the fluorine still existed in the form of calcium magnesium fluoride and sodium fluorosilicate was not formed. Therefore, the recovery rate of fluorine during the leaching process was not calculated and was represented by " / ".

[0119] It can be seen from Table 16 that when the method for resource utilization of fluorine in the recycling process of retired lithium batteries of the present application is adopted, the fluorine in the defluorinated slag can be effectively recovered and utilized. Among them, the recovery rate of fluorine element after leaching is above 95%, the overall recovery rate is above 90%, and the purity of the recovered product sodium fluoride is above 70%. The purity meets the basic utilization requirements and can be used without further purification steps.

[0120] It can be seen from the data of Example 1 and Comparative Example 1 that if one-stage leaching is adopted, the calcium in the defluorinated slag cannot be completely leached, while a large amount of fluorine is dissolved, resulting in a decrease in the fluorine content in the leaching residue and the inability to effectively recover and utilize the fluorine in the defluorinated slag. It can be seen from Example 1 and Comparative Example 2 that when the two-stage leaching residue reacts with the soda ash solution, if the reaction temperature is too low, the conversion is incomplete, resulting in a low purity of the obtained sodium fluoride.

[0121] It can be seen from Example 1 and Comparative Examples 2-8 that the parameters in the recovery process will affect the recovery rate of fluorine element in the defluorinated slag during the leaching process and the overall recovery rate of fluorine element. When the selected parameters are not within the range given in the present application, the recovery rate of fluorine element in the defluorinated slag and the overall recovery rate of fluorine element both show an obvious downward trend.

[0122] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present application rather than to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for the resource utilization of fluorine during the recycling of retired lithium batteries, characterized in that, it comprises the following steps: (1) Mix the defluorinated slag during the recycling of retired lithium batteries with liquid A, a first inorganic acid, and sodium silicate, and then heat and react. After the reaction ends, perform solid-liquid separation to obtain a first-stage leaching residue and a first-stage leaching solution; (2) Mix the first-stage leaching residue with water, a second inorganic acid, and sodium silicate, and then heat and react. After the reaction ends, perform solid-liquid separation to obtain a second-stage leaching residue and a second-stage leaching solution; (3) Mix the second-stage leaching residue with a soda ash solution and react. After the reaction ends, perform solid-liquid separation to obtain sodium fluoride; The liquid A is water or the second-stage leaching solution; In the step (1), the ratio of the sum of the molar amounts of calcium and magnesium elements in the defluorination slag to the molar amount of H + in the first inorganic acid is (0.4 - 0.8):1, and the ratio of the sum of the molar amounts of nickel, cobalt, and manganese in the defluorination slag to the molar amount of H + in the first inorganic acid is (0.06 - 0.15):1; the ratio of the molar amount of sodium silicate to the molar amount of H + in the first inorganic acid is (0.1 - 0.7):1, the temperature of the heating reaction is 60 - 150 °C, and the time is 1 - 4 h; In the step (2), the molar ratio of sodium silicate to H in the second inorganic acid + is (0.1 - 0.3):1, the temperature of the heating reaction is 60 - 150 °C, and the time is 3 - 6 h; In the step (3), the molar ratio of F in the secondary leaching residue to the molar amount of soda ash is 1:(0.4 - 1.2), the reaction temperature is 60 - 100 °C, and the time is 1 - 5 h. - ​ 2. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, in the step (1), the liquid-solid ratio of the liquid A to the defluorinated slag is (1.5 - 3) mL: 1 g.

3. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, In the step (2), the ratio of the sum of the molar amounts of calcium and magnesium elements in the first-stage leaching residue to the molar amount of H + in the second inorganic acid is (0.2 - 0.7):

1.

4. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, in the step (2), the liquid-solid ratio of the water to the first-stage leaching residue is (1 - 5) mL: 1 g.

5. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, in the step (3), the concentration of the soda ash is 150 - 300 g / L.

6. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, the first inorganic acid and the second inorganic acid are each independently selected from at least one of hydrochloric acid, nitric acid, and carbonic acid.

7. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, both the first inorganic acid and the second inorganic acid are selected from hydrochloric acid.

8. The method for the resource utilization of fluorine during the recycling of retired lithium batteries according to claim 1, characterized in that, the solid-liquid separation is carried out by means of pressure filtration.

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