Method for recycling waste lithium iron phosphate battery through total leaching process

Abstract

The invention discloses a method for recycling waste lithium iron phosphate batteries by a total leaching process, which comprises the following steps of: mixing an extracting agent with a diluent to obtain an organic phase; the waste lithium iron phosphate black powder and acid liquor are mixed for acid leaching, and total leachate is obtained; pumping the total leaching solution and a loaded organic phase into a multi-stage countercurrent reverse extraction box, and carrying out multi-stage countercurrent reverse extraction to obtain a lithium-rich solution and a regenerated organic phase; the lithium-rich liquid is subjected to impurity removal, evaporation concentration and lithium precipitation, and industrial-grade lithium carbonate and lithium-precipitated liquid are obtained; and simultaneously pumping the lithium-precipitated liquid and the organic phase and / or the regenerated organic phase into a multi-stage countercurrent extraction box, carrying out multi-stage countercurrent saponification extraction to obtain a loaded organic phase and raffinate, and returning the loaded organic phase to a reverse extraction process. According to the method, the liquid after lithium precipitation is treated through the extracting agent, efficient separation of lithium and sodium is achieved, the extracting agent can be subjected to acid pickling reverse extraction through the total leaching solution, the extracting agent is regenerated, meanwhile, the lithium concentration of the total leaching solution can be improved, and therefore the pH value adjustment of the acid leaching solution and the acid and alkali consumption of extracting agent acid pickling regeneration are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy battery recycling, and particularly relates to a method for cyclic recycling of a full leaching process of waste lithium iron phosphate batteries. Background Art

[0002] In recent years, with the innovation in lithium iron phosphate battery technology and applications, the rapid development of new energy vehicles and energy storage fields has been promoted, and lithium-ion batteries have been widely used. However, there is still a 5%-10% scrap rate of electrode sheets during the production of lithium iron phosphate batteries, and the number of retired and scrapped lithium iron phosphate batteries is also increasing. Therefore, the recycling of waste lithium iron phosphate batteries is extremely important.

[0003] Currently, the lithium content in the lithium precipitation waste liquid in the current waste lithium iron phosphate recycling process is still 1-6 g / L. If not further recycled, the lithium recovery rate of the overall process will be reduced. However, the lithium precipitation waste liquid also contains a sodium content close to the saturation concentration, resulting in an increase in the energy cost and reagent consumption cost of the lithium / sodium separation and recovery technology. At the same time, there are still many deficiencies in the full leaching process. For example, the acid concentration in the leaching solution is high in the acid leaching process, and the alkali consumption for pH adjustment is large.

[0004] There are many related technologies for recovering lithium from sodium carbonate lithium precipitation waste liquid. For example, in Chinese Patent Application CN118529752A, the lithium precipitation waste liquid (the liquid after lithium precipitation) is obtained by freezing separation technology to obtain industrial-grade sodium sulfate and the subsequent liquid, and the subsequent liquid is returned to leaching; in Chinese Patent Application CN116130817A, the liquid after lithium precipitation is used for lithium precipitation reaction with sodium phosphate, and after solid-liquid separation, lithium phosphate and sodium sulfate waste liquid are obtained. Lithium phosphate is post-treated to obtain battery-grade lithium phosphate, and the sodium sulfate waste liquid is treated to obtain sodium sulfate; Chinese Patent Application CN112661321A uses a lithium adsorption resin for lithium / sodium separation, and the desorbed liquid obtained by separation is refluxed to the lithium carbonate preparation system; in CN116607013A, the liquid after lithium precipitation is subjected to secondary evaporation and concentration treatment, and the concentrated liquid obtained is subjected to secondary lithium precipitation; in CN117778748A, extraction and back-extraction are used to extract lithium from the remaining solution of nickel, cobalt, and manganese in the recycling of ternary batteries. The obtained lithium sulfate solution can obtain battery-grade lithium carbonate and lithium precipitation mother liquor after lithium precipitation, and the lithium precipitation mother liquor is returned to the remaining solution of nickel, cobalt, and manganese.

[0005] In the above solutions, although the lithium extraction technology by adsorption method has low adsorbent cost, can be recycled, and is simple to operate, its adsorption capacity is low and the dissolution loss rate is high, resulting in high operating cost of the adsorbent; the energy consumption of freezing salt separation and evaporation crystallization technology is high, and the precipitation of sulfate is likely to cause a large amount of lithium loss. Although the extraction separation and recovery have good extraction separation and recovery effects, the acid concentration required for back-extraction is high, and the obtained lithium sulfate solution requires a large amount of liquid alkali to neutralize and adjust the pH to alkaline, resulting in high acid-base consumption cost. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention aims to provide a method for recycling the whole leaching process of waste lithium iron phosphate batteries.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for recycling the whole leaching process of waste lithium iron phosphate batteries, comprising the following steps:

[0009] S1. Prepare the organic phase: Mix the extractant and the diluent to obtain the organic phase;

[0010] S2. Whole leaching: Mix the waste lithium iron phosphate black powder and the acid solution for acid leaching to obtain the whole leaching solution; the reaction mechanism between the waste lithium iron phosphate black powder and the acid solution is:

[0011] LiFePO 4 +H + →Li + +Fe 2+ +H 3 PO 4

[0012] S3. Back extraction: Pump the whole leaching solution and the loaded organic phase into a multi-stage countercurrent back extraction tank for multi-stage countercurrent back extraction to obtain a lithium-rich solution and a regenerated organic phase; the general formula of the back extraction mechanism is:

[0013] P204-Li+H + →P204-H+Li +

[0014] S4. Lithium precipitation: The lithium-rich solution obtained in step S3 is successively subjected to impurity removal, evaporation concentration and lithium precipitation to obtain industrial-grade lithium carbonate and the solution after lithium precipitation;

[0015] S5. Extraction: Simultaneously pump the solution after lithium precipitation, the organic phase prepared in step S1 and / or the regenerated organic phase obtained in step S3 into a multi-stage countercurrent extraction tank for multi-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the loaded organic phase returns to the back extraction process of step S3.

[0016] Further, in step S1, the volume ratio of the extractant to the diluent is 1:(1-3).

[0017] Further, in step S1, the extractant is at least one of 4-methyl-10-hydroxybenzoquinoline, Sudan I, FSH, TOPO, P204, P507, C272; the diluent is sulfonated kerosene.

[0018] Further, in step S2, the acid solution is one or a mixture of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid.

[0019] Further, in step S2, the mass-volume ratio of the waste lithium iron phosphate black powder to the acid solution is 1:(3 - 10) g / ml, and the acid solution concentration is 2 - 4 mol / L.

[0020] Further, in step S3, the volume ratio of the total leaching solution to the loaded organic phase is (1 - 5):1; the single-stage stripping time is 10 - 60 min, and the stripping temperature is 30 - 60 °C; the number of stages of multi-stage countercurrent stripping is 3 - 10; the pH of the lithium-rich solution is 0.5 - 1.

[0021] Further, in step S4, after the lithium-rich solution is purified and evaporated and concentrated, the Li concentration is 16 - 18 g / L.

[0022] Further, in step S4, the Li concentration of the solution after lithium precipitation is 2 - 6 g / L.

[0023] Further, in step S5, saponification extraction is used; the volume ratio of the solution after lithium precipitation to the organic phase and / or the regenerated organic phase is (1 - 5):1; the single-stage extraction time is 10 - 30 min, and the extraction temperature is 30 - 60 °C; the number of stages of multi-stage countercurrent saponification extraction is 3 - 7.

[0024] The solution after lithium precipitation is alkaline (pH is about 13 - 14), which contains a large amount of Na and a small amount of Li. Therefore, saponification is mainly based on NaOH and supplemented by LiOH. At the same time, the extractant has a stronger selectivity for Li than for Na, and the Li / Na extraction exchange occurs simultaneously. The reaction mechanism of saponification extraction is:

[0025] P204-H + LiOH → P204-Li + H 2 O

[0026] P204-H + NaOH → P204-Na + H 2 O

[0027] P204-Na + Li + → P204-Li + Na +

[0028] Further, in step S5, the main component of the raffinate is sodium sulfate, and the lithium concentration is < 0.1 g / L.

[0029] The beneficial effects of the present invention are as follows: The present invention provides a method for recycling the waste lithium battery by a full leaching process cycle. Compared with the general full leaching recovery method, the present invention uses an extractant to treat the solution after lithium precipitation to achieve efficient separation of lithium and sodium. The loaded extractant can be stripped by pickling with the full leaching solution to realize the regeneration of the extractant. At the same time, the lithium concentration of the full leaching solution can be increased, thereby reducing the acid-base consumption for adjusting the pH of the acid leaching solution and pickling and regenerating the extractant. Description of the Drawings

[0030] Figure 1 This is the flowchart of the method of Embodiments 1-3 of the present invention. Detailed implementation manners

[0031] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0032] Embodiment 1

[0033] This embodiment provides a method for recycling the whole-leaching process of waste lithium iron phosphate batteries, including the following steps:

[0034] S1. Prepare the organic phase: Mix the extractant P204 and the diluent sulfonated kerosene in a volume ratio of 1:1 to obtain a light yellow transparent organic phase.

[0035] S2. Whole-leaching: Leach the black powder of waste lithium iron phosphate batteries with 2 mol / L sulfuric acid solution under the conditions of a solid-liquid ratio of 1:3 and a temperature of 60 °C for 2 h to obtain graphite slag and a whole-leaching solution with a lithium concentration of 8.27 g / L.

[0036] S3. Back-extraction: Pump the whole-leaching solution obtained in step S2 and the loaded organic phase P204-Li into a 3-stage countercurrent back-extraction box at a volume ratio of 3:1. After 3-stage countercurrent back-extraction, the back-extraction time for each stage is 30 min at a temperature of 50 °C to obtain a lithium-rich solution and the regenerated organic phase P204. The pH of the lithium-rich solution is 0.5.

[0037] S4. Lithium precipitation: After the lithium-rich solution obtained in step S3 is successively subjected to impurity removal and evaporation concentration to obtain a lithium-rich solution with a pH of 14 and a lithium concentration of 17.5 g / L, add saturated sodium carbonate for lithium precipitation to obtain industrial-grade lithium carbonate and a lithium-precipitated solution with a lithium concentration of 5 g / L.

[0038] S5. Extraction: Pump the lithium-precipitated solution obtained in step S4 and the organic phase (initially the organic phase prepared in step S1 and the regenerated organic phase obtained in step S3 after recycling) into a 5-stage countercurrent extraction box at a volume ratio of 2:1. After 5-stage countercurrent saponification extraction, keep the extraction time for each stage at 30 min and the extraction temperature at 50 °C. Obtain the loaded organic phase P204-Li and a raffinate with a lithium concentration of 0.07 g / L. The loaded organic phase P204-Li is returned to the back-extraction process of step S3.

[0039] Embodiment 2

[0040] This embodiment provides a method for recycling the whole-leaching process of waste lithium iron phosphate batteries, including the following steps:

[0041] S1. Preparation of organic phase: Mix the extractant P204 and the diluent sulfonated kerosene in a volume ratio of 1:2 to obtain a light yellow transparent organic phase.

[0042] S2. Complete leaching: Leach the black powder of waste lithium iron phosphate batteries with 3 mol / L hydrochloric acid solution under the conditions of a solid-liquid ratio of 1:3 and a temperature of 60 °C for 2 h to obtain graphite slag and a complete leaching solution with a lithium concentration of 8.27 g / L.

[0043] S3. Back extraction: Pump the complete leaching solution obtained in step S2 and the loaded organic phase P204-Li into a 4-stage countercurrent back extraction box simultaneously at a volume ratio of 2:1. After 4-stage countercurrent back extraction, perform back extraction for 30 min at each stage at a temperature of 50 °C to obtain a lithium-rich solution and the regenerated organic phase P204. The pH of the lithium-rich solution is 0.5.

[0044] S4. Lithium precipitation: Sequentially subject the lithium-rich solution obtained in step S3 to impurity removal and evaporation concentration. After obtaining a solution with a pH of 14 and a lithium concentration of 17.6 g / L, add saturated sodium carbonate for lithium precipitation to obtain industrial-grade lithium carbonate and a lithium precipitation solution with a lithium concentration of 4.8 g / L.

[0045] S5. Extraction: Pump the lithium precipitation solution obtained in step S4 and the organic phase (initially the organic phase prepared in step S1 and the regenerated organic phase obtained in step S3 after recycling) into a 6-stage countercurrent extraction box simultaneously at a volume ratio of 4:3. After 6-stage countercurrent saponification extraction, keep the extraction time at each stage for 30 min and the extraction temperature at 50 °C. Obtain the loaded organic phase P204-Li and a raffinate with a lithium concentration of 0.03 g / L.

[0046] Example 3

[0047] This example provides a method for recycling the complete leaching process of waste lithium iron phosphate batteries, including the following steps:

[0048] S1. Preparation of organic phase:

[0049] Mix the extractant P204 and the diluent sulfonated kerosene in a volume ratio of 1:1 to obtain a light yellow transparent organic phase.

[0050] S2. Complete leaching: Leach the black powder of waste lithium iron phosphate batteries with 2 mol / L sulfuric acid solution under the conditions of a solid-liquid ratio of 1:5 and a temperature of 60 °C for 2 h to obtain graphite slag and a complete leaching solution with a lithium concentration of 5.02 g / L.

[0051] S3. Back extraction: Pump the complete leaching solution obtained in step S2 and the loaded organic phase P204-Li into a 3-stage countercurrent back extraction box simultaneously at a volume ratio of 5:1. After 3-stage countercurrent back extraction, perform extraction for 30 min at each stage at a temperature of 50 °C and adjust the pH of the back extraction outlet liquid phase to 0.5 to obtain a lithium-rich solution and the regenerated organic phase P204.

[0052] S4. Lithium precipitation: The lithium-rich solution obtained in step S3 is successively subjected to impurity removal and evaporation concentration. After obtaining a solution with a pH of 14 and a lithium concentration of 17.0 g / L, saturated sodium carbonate is added for lithium precipitation to obtain industrial-grade lithium carbonate and a post-lithium-precipitation solution with a lithium concentration of 5.2 g / L.

[0053] S5. Extraction: The post-lithium-precipitation solution obtained in step S4 and the organic phase (initially the organic phase prepared in step S1, and the recycled regenerated organic phase obtained in step S3 is used after recycling) are simultaneously pumped into a 5-stage countercurrent extraction box at a volume ratio of 2:1. After 5-stage countercurrent saponification extraction, the extraction time for each stage is maintained at 30 min, and the extraction temperature is 50 °C. A loaded organic phase P204-Li and a raffinate with a lithium concentration of 0.08 g / L are obtained.

[0054] For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all such changes and deformations should be included within the protection scope of the claims of the present invention.

Claims

1. A method for recycling waste lithium iron phosphate batteries by full leaching process, characterized in that: The following steps are involved: S1. preparing an organic phase: mixing an extractant and a diluent to obtain an organic phase; S2, full leaching: mixing the waste lithium iron phosphate black powder and acid solution for acid leaching to obtain a full leaching solution; S3, stripping: pumping the whole leachate and the loaded organic phase into a multi-stage countercurrent stripping box for multi-stage countercurrent stripping to obtain a lithium-rich solution and a regenerated organic phase; S4, lithium precipitation: the lithium-rich solution obtained in step S3 is subjected to impurity removal, evaporation concentration and lithium precipitation in sequence to obtain industrial-grade lithium carbonate and a solution after lithium precipitation; S5, extraction: the liquid after lithium precipitation and the organic phase obtained in step S1 and / or the regenerated organic phase obtained in step S3 are simultaneously pumped into a multi-stage countercurrent extraction box for multi-stage countercurrent extraction to obtain a loaded organic phase and a raffinate, and the loaded organic phase is returned to the stripping process of step S3.

2. The method according to claim 1, characterized in that In step S1, the volume ratio of the extractant to the diluent is 1:(1-3).

3. The method according to claim 1, characterized in that In step S1, the extractant is at least one of 4-methyl-10-hydroxybenzoquinoline, Sudan I, FSH, TOPO, P204, P507, and C272; and the diluent is sulfonated kerosene.

4. The method according to claim 1, characterized in that: In step S2, the acid solution is a mixture of one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

5. The method according to claim 1, characterized in that In step S2, the mass volume ratio of the waste lithium iron phosphate black powder and the acid solution is 1:(3-10) in g / ml, and the concentration of the acid solution is 2-4 mol / L.

6. The method according to claim 1, characterized in that In step S3, the volume ratio of the total leachate to the loaded organic phase is (1-5):1; the single-stage stripping time is 10-60min, and the stripping temperature is 30-60°C; the number of stages of the multi-stage countercurrent stripping is 3-10; and the pH of the lithium-rich solution is 0.5-1.

7. The method according to claim 1, characterized in that In step S4, after the lithium-rich solution is removed from impurities and concentrated by evaporation, the Li concentration is 16-18 g / L.

8. The method according to claim 1, characterized in that In step S4, the Li concentration of the solution after lithium precipitation is 2-6 g / L.

9. The method according to claim 1, characterized in that: In step S5, extraction is performed by saponification extraction; the volume ratio of the lithium precipitation liquid to the organic phase and / or the regenerated organic phase is (1-5):1; the single-stage extraction time is 10-30min, and the extraction temperature is 30-60°C; the number of stages of multi-stage countercurrent saponification extraction is 3-7.

10. The method according to claim 1, characterized in that In step S5, the main component of the raffinate is sodium sulfate, wherein the lithium concentration is less than 0.1 g / L.

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