A method for improving the lithium recovery rate from waste lithium batteries

Abstract

The present invention discloses a method for improving the lithium recovery rate from waste lithium batteries. First, the lithium iron phosphate battery is discharged, disassembled, the lithium iron phosphate battery core is crushed, dried, and the organic battery powder, copper foil, aluminum foil and diaphragm plastic are separated; the organic battery powder is pyrolyzed to obtain battery powder; the battery powder is added to a mixed solution of sulfuric acid and an auxiliary agent, impregnated and filtered to obtain a filter residue and a filtrate, the filter residue is washed to obtain crude iron phosphate, iron powder is added for impurity removal and then filtered for the second time, alkali is added to the filtrate for secondary impurity removal, filtered for the third time, filtered, oxidized, liquid alkali is added, and after the fourth filtration, a filter residue and a lithium sulfate solution are obtained, the filter residue is washed and filtered to obtain crude iron phosphate, and the lithium sulfate solution is added with lime and caustic soda to obtain a lithium sulfate solution and calcium residue. The operation of the present invention is simple, easy for large-scale industrial production, and the raw materials used in the process are all substances that are easily obtained in industry and have low costs.

Description

Technical Field

[0001] The present invention belongs to the field of battery recycling, relates to a method for recycling lithium batteries, and particularly relates to a method for improving the recovery rate of lithium in waste lithium batteries. Background Art

[0002] In order to address climate change and carbon emissions and achieve the goals of "carbon peak" and "carbon neutrality", the demand for high-energy-density and long-life lithium batteries in the electric vehicle field has surged. It is speculated that by 2025, the global demand for lithium-ion batteries will reach approximately 1700 GWh, and by 2030, it will reach 4700 GWh. With the market expansion, a large number of lithium batteries will face retirement. The main pollutants contained in the batteries include heavy metals and electrolyte solutions such as acids and alkalis. If waste lithium batteries are not properly disposed of, it will cause environmental pollution and harm to the human body. In addition, these waste batteries contain a large amount of valuable metals, such as lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al), and copper (Cu). Therefore, from the perspectives of resource recovery and environmental protection, it is of great significance to effectively recover the metal elements of a large number of lithium batteries.

[0003] The metals such as Cu, Li, Al, and Fe contained in lithium iron phosphate batteries are all precious resources, among which the contents of copper and lithium are as high as 10% and 1.80% respectively. Lithium present on the positive electrode is the most valuable substance for recycling in lithium-ion batteries due to its high price and scarce resources.

[0004] From the perspective of the leaching technology of valuable metals from retired lithium-ion batteries, high-temperature calcination or treatment with strong acids and alkalis is the current mainstream technology, but these technologies have high energy consumption and great harmfulness. From the perspective of the resource regeneration technology of retired lithium-ion batteries, the research on the selective separation and purification of multiple metals is still lacking, especially for the doping modification of the current cathode materials, which increases the difficulty of separation and purification. Therefore, developing an efficient, low-cost, and pollution-free waste lithium battery recycling process has important application value. Summary of the Invention

[0005] The present invention overcomes the existing defects and provides a method for improving the recovery rate of lithium in waste lithium batteries. This method can effectively improve the recovery rate of lithium.

[0006] The technical solution of the present invention is as follows.

[0007] A method for improving the recovery rate of lithium in waste lithium batteries, comprising the following steps:

[0008] (1) First, discharge the lithium iron phosphate battery, then disassemble it to remove the outer shell and copper busbar, crush the lithium iron phosphate battery core, dry it at low temperature, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and diaphragm plastic;

[0009] (2) Pyrolyze the organic battery powder obtained in step (1) to obtain battery powder;

[0010] (3) Add the battery powder to a mixed solution of sulfuric acid and an auxiliary agent, impregnate it at 60-100 °C, filter after impregnation to obtain a filter residue and a filtrate. The filter residue is washed to obtain crude iron phosphate. After the filtrate is taken out, iron powder is added for impurity removal and then filtered for the second time. Alkali is added to the filtrate for secondary impurity removal, and then filtered for the third time. After filtration, the filtrate is subjected to oxidation treatment, and then liquid alkali is added. After filtration for the fourth time, a filter residue and a lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. The lithium sulfate solution is added with lime and caustic soda to obtain a lithium sulfate solution and calcium slag.

[0011] In the above method, in step (1), the discharging treatment is: placing the lithium iron battery in a saturated KCl solution, and the soaking time is 12-54 h.

[0012] In the above method, in step (1), the temperature of the low-temperature drying is 120-150 °C, and the time of the low-temperature drying is: 1-2 h.

[0013] In the above method, in step (2), the pyrolysis is: high-temperature pyrolysis is carried out after low-temperature drying, the high-temperature pyrolysis temperature is 300-550 °C, and the pyrolysis time is 0.5-1.5 h.

[0014] In the above method, in step (3), the auxiliary agent is one or more of compressed air, hydrogen peroxide, sodium chlorate, and sodium persulfate.

[0015] In the above method, in step (3), the mass percentage concentration of the sulfuric acid is 98%.

[0016] In the above method, in step (3), the impregnation time is: 3-6 h.

[0017] In the above method, in step (3), the oxidation treatment is to introduce compressed air; the flow rate of the compressed air is 5-20 L / min

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] The operation of the present invention is simple, easy to carry out large-scale industrial production, and the raw materials used in the process are all substances that are easy to obtain and have low costs in industry.

[0020] In the present invention, for the treatment step of battery powder with sulfuric acid and additives, an operation of impregnating at 50-100 °C for 3-5 h is adopted. This operation can reduce the moisture content of the leaching residue, improve the metal recovery rate of lithium, with the leaching rate of lithium > 98%, and reduce the leaching of impurities, reducing the amount of output slag for the next-step purification and impurity removal of lithium sulfate solution. To meet the requirements of industrial production, compressed air is used for oxidation treatment in this application, and the key flow rate data is given, greatly reducing the production cost. Detailed implementation mode

[0021] To better illustrate the present invention and facilitate understanding of its technical solution, typical but non-limiting embodiments of the present invention are as follows. Embodiment

[0022] (1) First, place the lithium iron battery in a saturated KCl solution for 20 h of soaking, then disassemble it to remove the outer shell and copper busbar, crush the lithium iron battery core, dry it at a low temperature of 120 °C for 1 h, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and diaphragm plastic.

[0023] (2) Pyrolyze the organic battery powder obtained in step (1), specifically pyrolyze it at 550 °C for 1.5 h to obtain battery powder.

[0024] (3) Add 100 g of battery powder to a mixed solution of 50 ml of 98% sulfuric acid and 7% hydrogen peroxide, where the mass ratio of the sulfuric acid solution to hydrogen peroxide is 1:1. Impregnate at 100 °C for 6 h, filter after impregnation to obtain filter residue and filtrate. The filter residue is washed to obtain crude iron phosphate. After the filtrate is taken out, iron powder is added for impurity removal and then filtered for the second time. NaOH is added to the filtrate for secondary impurity removal, and then filtered for the third time. After filtration, compressed air is introduced into the filtrate at a flow rate of 5 L / min, and 35% NaOH solution is added. After the fourth filtration, filter residue and lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. Lime and flake soda are added to the lithium sulfate solution to obtain lithium sulfate solution and calcium slag.

[0025] In this embodiment, the lithium recovery rate > 97%; the lithium content in the leaching residue < 0.05%. Calculated based on the lithium content of 3.0% in the raw material and the leaching residue rate of 105% (dry basis), the leaching rate = 0.05% * 105 / 3.0% * 100 = 98.25%; due to the adoption of the present invention, there are few impurities in the leaching solution (the main controllable leaching impurities are iron and phosphorus). Therefore, the lithium content in the impurity removal slag during oxidation treatment for impurity removal is low, and the lithium content in the impurity removal slag can reach < 0.1%, and the impurity removal slag rate (relative to the raw material input) < 15%. The lithium recovery rate in the whole process > 97%. Embodiment

[0026] (1) First, place the lithium iron phosphate battery in a saturated KCl solution for 20 h of soaking. Then, disassemble it to remove the outer shell and copper busbars, crush the lithium iron phosphate battery core, dry it at a low temperature of 150 °C for 2 h, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and separator plastic.

[0027] (2) Pyrolyze the organic battery powder obtained in step (1), specifically pyrolyze it at 500 °C for 1 h to obtain battery powder.

[0028] (3) Add 100 g of battery powder to a mixed solution of 50 ml of 98% sulfuric acid and 7% hydrogen peroxide, where the mass ratio of the sulfuric acid solution to hydrogen peroxide is 1:1.5. Immerse it at 100 °C for 6 h. After immersion, filter to obtain a filter residue and a filtrate. The filter residue is washed to obtain crude iron phosphate. The filtrate is taken out, iron powder is added for impurity removal, and then filtered for the second time. NaOH is added to the filtrate for secondary impurity removal, and then filtered for the third time. After filtration, compressed air is introduced into the filtrate at a flow rate of 20 L / min, and 32% NaOH solution is added. After the fourth filtration, a filter residue and a lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. The lithium sulfate solution is added with lime and caustic soda to obtain a lithium sulfate solution and calcium slag.

[0029] In this example, the lithium recovery rate > 98%; the lithium content in the leaching residue < 0.05%.

[0030] Comparative Example 1

[0031] (1) First, place the lithium iron phosphate battery in a saturated KCl solution for 20 h of soaking. Then, disassemble it to remove the outer shell and copper busbars, crush the lithium iron phosphate battery core, dry it at a low temperature of 120 °C for 1 h, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and separator plastic.

[0032] (2) Pyrolyze the organic battery powder obtained in step (1), specifically pyrolyze it at 550 °C for 1.5 h to obtain battery powder.

[0033] (3) Add 100 g of battery powder to 50 ml of 98% sulfuric acid, immerse it at 100 °C for 6 h. After immersion, filter to obtain a filter residue and a filtrate. The filter residue is washed to obtain crude iron phosphate. The filtrate is taken out, iron powder is added for impurity removal, and then filtered for the second time. NaOH is added to the filtrate for secondary impurity removal, and then filtered for the third time. After filtration, compressed air is introduced into the filtrate at a flow rate of 5 L / min, and 35% NaOH solution is added. After the fourth filtration, a filter residue and a lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. The lithium sulfate solution is added with lime and caustic soda to obtain a lithium sulfate solution and calcium slag.

[0034] The difference between this comparative example and Example 1 lies in that in step (3), battery powder is added to sulfuric acid. After testing, the lithium recovery rate in this comparative example is about 78%.

[0035] Comparative Example 2

[0036] (1) First, place the lithium iron phosphate battery in a saturated KCl solution for 20 h of soaking, then disassemble it to remove the outer shell and copper busbar, crush the lithium iron phosphate battery core, dry it at a low temperature of 120 °C for 1 h, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and diaphragm plastic;

[0037] (2) Pyrolyze the organic battery powder obtained in step (1), specifically pyrolyze it at 550 °C for 1.5 h to obtain battery powder;

[0038] (3) Add 100 g of battery powder to a mixed solution of 50 ml of 98% sulfuric acid and 7% hydrogen peroxide, where the mass ratio of the sulfuric acid solution to hydrogen peroxide is 1:1, impregnate it at room temperature for 6 h, filter after impregnation to obtain a filter residue and a filtrate. The filter residue is washed to obtain crude iron phosphate. After the filtrate is taken out, iron powder is added for impurity removal and then filtered a second time. NaOH is added to the filtrate for secondary impurity removal, and then filtered a third time. After filtration, compressed air is introduced into the filtrate at a flow rate of 5 L / min, and 35% NaOH solution is added. After the fourth filtration, a filter residue and a lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. Lime and flake soda are added to the lithium sulfate solution to obtain a lithium sulfate solution and calcium slag.

[0039] The difference between this comparative example and Example 1 is that the impregnation temperature in step (3) is room temperature. After testing, the lithium recovery rate in this comparative example is 84%.

[0040] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for improving the lithium recovery rate in waste lithium batteries, characterized in that, The method includes the following steps: (1) First, place the lithium iron phosphate battery in a saturated KCl solution and soak it for 20 h. Then, disassemble it to remove the outer shell and copper busbars, crush the lithium iron phosphate battery core, dry it at a low temperature of 150 °C for 2 h, and screen out iron to separate out organic battery powder, copper foil, aluminum foil, and diaphragm plastic; (2) Pyrolyze the organic battery powder obtained in step (1), specifically pyrolyze it at 500 °C for 1 h to obtain battery powder; (3) Add 100 g of the battery powder to a mixed solution of 50 ml of 98% sulfuric acid and 7% hydrogen peroxide, where the mass ratio of the sulfuric acid solution to hydrogen peroxide is 1:1.

5. Immerse it at 100 °C for 6 h. After immersion, filter to obtain a filter residue and a filtrate. The filter residue is washed to obtain crude iron phosphate. After the filtrate is taken out, iron powder is added for impurity removal and then filtered for the second time. NaOH is added to the filtrate for secondary impurity removal, and then filtered for the third time. After filtration, compressed air is introduced into the filtrate at a flow rate of 20 L / min, and 32% NaOH solution is added. After the fourth filtration, a filter residue and a lithium sulfate solution are obtained. The filter residue is washed and filtered to obtain crude iron phosphate. The lithium sulfate solution is added with lime and caustic soda to obtain a lithium sulfate solution and calcium slag; In this method, the lithium recovery rate > 98%; the lithium content in the leaching residue < 0.05%.