A method for extracting lithium elements from waste batteries

Abstract

The present invention belongs to the technical field of lithium battery waste recycling, and particularly relates to a method for extracting lithium elements from waste batteries. First, the waste batteries are charged to cause lithium to accumulate at the negative electrode graphite and embed the lithium into the graphite. Subsequently, crushing treatment is carried out underwater, and a large amount of water is used to absorb heat and isolate oxygen, avoiding the thermal runaway phenomenon caused by charging during the crushing process. At the same time of crushing, the graphite negative electrode can be desorbed from the electrode sheet into the water, and the graphite negative electrode is separated by foam flotation using the hydrophobicity of graphite and at the same time the embedded lithium ions are carried out. Subsequently, acid solution is used to recover lithium elements by leaching. The present invention adopts the method of extracting most of the lithium in advance and a small part of the lithium in the later stage for recycling, preferentially extracting pure lithium elements in a simple way and reducing the loss of lithium caused by later-stage lithium extraction; recycling the raffinate liquid, reducing the consumption of other materials while improving the lithium recovery rate. The method of the present invention is simple and the lithium recovery rate is relatively high.

Description

Technical Field

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

[0002] At present, the richness of elements in waste ternary batteries has led to difficulties in extracting high-purity lithium; in addition to valuable elements such as nickel, cobalt, and manganese, there are also other impurity elements such as copper, aluminum, calcium, and magnesium in the leaching solution. The methods for recovering lithium elements from waste batteries are mainly divided into pre-lithium extraction and post-lithium extraction. The pre-lithium extraction method is to use acid solution to leach lithium elements for recovery, but it is inevitable to bring out more impurities during the process, resulting in the need for multiple steps of impurity removal in the follow-up. Although post-lithium extraction can naturally place lithium elements at the end of the process for recovery to improve purity when extracting other elements in the early stage, part of the lithium will inevitably be lost during the extraction of other elements, reducing the recovery rate. Summary of the Invention

[0003] In view of this, the present invention provides a method for extracting lithium elements from waste batteries. The method provided by the present invention is simple and easy to operate, and has a high recovery rate for lithium elements.

[0004] To solve the above technical problems, the present invention provides a method for extracting lithium elements from waste batteries, including the following steps:

[0005] Charge the waste lithium-ion battery and then perform underwater crushing to obtain a slurry;

[0006] Perform bubble flotation on the slurry to obtain waste graphite and a mixed slurry respectively;

[0007] Perform first leaching on the waste graphite in a first acid solution to obtain a lithium-containing solution;

[0008] Roast and screen the mixed slurry, and take the undersize to obtain waste cathode materials;

[0009] Mix the waste cathode materials, a second acid solution, and a reducing agent for second leaching to obtain a leaching solution;

[0010] Perform multi-stage extraction on the leaching solution to obtain a raffinate;

[0011] Reuse the raffinate for the first leaching.

[0012] Preferably, the charging is to charge the waste lithium-ion battery to saturation.

[0013] Preferably, the bubble flotation includes the following steps:

[0014] Place the slurry in a flotation device, stir it for the first time and then introduce foam, and then stir it for the second time and introduce air after entering the flotation cell.

[0015] Preferably, the rotation speed of the first stirring is 500 - 1500 rpm, and the time of the first stirring is 5 - 30 min;

[0016] The concentration of foam in the system after introducing foam is 5 - 20 ppm;

[0017] The rotation speed of the second stirring is 500 - 1500 rpm, and the time of the second stirring is 5 - 30 min;

[0018] The flow rate of introduced air is 1 - 10 L / min, and the time of introducing air is 4 - 6 min.

[0019] Preferably, the molar concentration of hydrogen ions in the first acid solution is 1 - 4 mol / L, and the mass ratio of the waste graphite to the first acid solution is 1:2 - 4;

[0020] The time of the first leaching is 1 - 4 h. The first leaching is accompanied by stirring, and the rotation speed of the stirring is 100 - 400 r / min.

[0021] Preferably, the pH value of the raffinate is 4.5 - 5.0;

[0022] Before recycling the raffinate to the first leaching, it further includes: adjusting the pH value of the raffinate to the pH value required by the first acid solution.

[0023] Preferably, the temperature of the roasting is 400 - 800 °C, and the heat preservation time of the roasting is 1 - 4 h.

[0024] Preferably, the screening includes multi - stage screening; the particle size of the waste cathode material is less than 100 mesh.

[0025] Preferably, the molar concentration of hydrogen ions in the second acid solution is 1 - 4 mol / L, and the mass ratio of the waste cathode material to the second acid solution is 1:4 - 10;

[0026] The reducing agent includes sodium thiosulfate or hydrogen peroxide; the mass ratio of the waste cathode material to the reducing agent is 1:0.2 - 0.5;

[0027] The temperature of the second leaching is 50 - 95 °C, the time of the second leaching is 2 - 4 h. The second leaching is accompanied by stirring, and the rotation speed of the stirring is 100 - 400 r / min.

[0028] Preferably, the multi - stage extraction includes first extraction, second extraction, third extraction, and fourth extraction carried out in sequence;

[0029] The first extractant for extraction is P204 extractant, the second extractant for extraction is P204 extractant, the third extractant for extraction is P507 extractant, and the fourth extractant for extraction is P507 extractant.

[0030] The present invention provides a method for extracting lithium elements from waste batteries, comprising the following steps: charging the waste lithium-ion battery and then performing underwater crushing to obtain a slurry; performing bubble flotation on the slurry to obtain waste graphite and a mixed slurry respectively; performing a first leaching of the waste graphite in a first acid solution to obtain a lithium-containing solution; roasting and screening the mixed slurry, and taking the undersize to obtain waste cathode materials; mixing the waste cathode materials, a second acid solution and a reducing agent for a second leaching to obtain a leaching solution; performing multi-stage extraction on the leaching solution to obtain a raffinate; and recycling the raffinate to the first leaching. In the present invention, the waste battery is first charged to cause the lithium in the battery to aggregate at the negative electrode graphite and embed the lithium in the graphite, and then underwater crushing is performed. A large amount of water is used to absorb heat and isolate oxygen, avoiding the thermal runaway phenomenon caused by electrification during the crushing process; the binder of the graphite negative electrode is mainly a water-based binder such as CMC. Therefore, during the crushing, the graphite negative electrode can be desorbed from the electrode plate into the water, and the hydrophobicity of the graphite is utilized to separate the graphite negative electrode by foam flotation and simultaneously carry out the embedded lithium ions; subsequently, acid solution is used to recover lithium elements by leaching. The present invention adopts a method of extracting most of the lithium in the front and a small part of the lithium in the back for recovery, preferentially extracting pure lithium elements in a simple manner and reducing the loss of lithium caused by subsequent lithium extraction. The present invention separates lithium elements while separating graphite, simplifies the separation and purification steps, eliminates the battery discharging step process, and reduces the equipment requirements during the crushing process; recycling the raffinate reduces the consumption of other materials while increasing the lithium recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process flow diagram of the method for extracting lithium elements from waste batteries provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention provides a method for extracting lithium elements from waste batteries, comprising the following steps:

[0033] Charging the waste lithium-ion battery and then performing underwater crushing to obtain a slurry;

[0034] Performing bubble flotation on the slurry to obtain waste graphite and a mixed slurry respectively;

[0035] Performing a first leaching of the waste graphite in a first acid solution to obtain a lithium-containing solution;

[0036] Roasting and screening the mixed slurry, and taking the undersize to obtain waste cathode materials;

[0037] Mix the waste cathode material, the second acid solution and a reducing agent for a second leaching to obtain a leaching solution;

[0038] Perform multi-stage extraction on the leaching solution to obtain a raffinate;

[0039] Reuse the raffinate for the first leaching.

[0040] In the present invention, if not otherwise specified, all materials are conventional commercially available products.

[0041] In the present invention, the waste lithium-ion battery is charged and then broken underwater to obtain a slurry. As a specific embodiment of the present invention, the charging may be to charge the waste lithium-ion battery to saturation. The present invention utilizes the principle that lithium elements will be embedded in the graphite negative electrode after the battery is charged. First, the waste battery is charged so that the lithium in the battery accumulates in the negative electrode graphite.

[0042] As a specific embodiment of the present invention, the breaking can be carried out in a crusher; the present invention has no special requirements for the underwater breaking, and conventional methods in the art can be used. The present invention breaks underwater and can absorb heat and isolate oxygen through a large amount of water, avoiding the thermal runaway phenomenon caused by electrification during the breaking process; at the same time, the binder of the graphite negative electrode is mainly water-based binders such as CMC, so the graphite negative electrode can be desorbed from the electrode sheet into the water during the breaking process.

[0043] After obtaining the slurry, the present invention performs bubble flotation on the slurry to obtain waste graphite and a mixed slurry respectively. As a specific embodiment of the present invention, the bubble flotation may include the following steps: place the slurry in a flotation device, stir it for the first time and then introduce foam, stir it for the second time after entering the flotation tank, and introduce air. As a specific embodiment of the present invention, the rotation speed of the first stirring may be 500-1500 rpm, may also be 800-1300 rpm, and may further be 1000-1200 rpm; the time of the first stirring may be 5-30 min, may also be 10-20 min, and may further be 15-18 min; the concentration of foam in the system after introducing the foam may be 5-20 ppm, may also be 10-15 ppm; the rotation speed of the second stirring may be 500-1500 rpm, may also be 800-1300 rpm, and may further be 1000-1200 rpm; the time of the second stirring may be 5-30 min, may also be 10-20 min, and may further be 15-18 min; the flow rate of the introduced air may be 1-10 L / min, may also be 3-8 L / min, and may further be 5-7 L / min; the time of introducing air may be 4-6 min, and may specifically be 4 min, 5 min or 6 min.

[0044] In the present invention, the waste graphite is located in the upper liquid after bubble flotation, and the lower liquid is a mixed slurry, and the main component in the mixed slurry is black powder.

[0045] After obtaining the waste graphite, the present invention performs a first leaching of the waste graphite in a first acid solution to obtain a lithium-containing solution. As a specific embodiment of the present invention, before the first leaching, it may further include: washing the waste graphite with water. As a specific embodiment of the present invention, the first acid solution may be an aqueous sulfuric acid solution or an aqueous hydrochloric acid solution; the molar concentration of hydrogen ions in the first acid solution may be 1-4 mol / L, and may also be 2-3 mol / L; the mass ratio of the waste graphite to the first acid solution may be 1:2-4, specifically 1:2, 1:3 or 1:4. As a specific embodiment of the present invention, the time of the first leaching may be 1-4 h, and may also be 2-3 h; the first leaching may be accompanied by stirring, and the rotation speed of the stirring may be 100-400 r / min, and may also be 200-300 r / min. As a specific embodiment of the present invention, the pH value of the system during the first leaching may be 0-1.5, and the present invention can adjust the pH value of the system during the first leaching by adjusting the addition amount of the first acid solution.

[0046] After obtaining the mixed slurry, the present invention calcines and sieves the mixed slurry, and takes the undersize to obtain waste cathode materials. As a specific embodiment of the present invention, before the calcination, it may further include: filtering the mixed slurry to remove the filtrate. As a specific embodiment of the present invention, the temperature of the calcination may be 400-800 °C, specifically 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C; the heat preservation time of the calcination may be 1-4 h, specifically 1 h, 2 h, 3 h or 4 h.

[0047] In the present invention, the organic substances such as binders and plastics in the mixed slurry can be removed by pyrolysis after calcination. As a specific embodiment of the present invention, the sieving may include multi-stage sieving; the particle size of the waste cathode materials is less than 100 mesh, and the present invention has no special requirements for the aperture of the sieve mesh used in the multi-stage sieving, as long as the waste cathode materials with a particle size less than 100 mesh can be obtained.

[0048] After obtaining the waste cathode material, the present invention mixes the waste cathode material, a second acid solution and a reducing agent for a second leaching to obtain a leaching solution. As a specific embodiment of the present invention, the second acid solution may be an aqueous sulfuric acid solution or an aqueous hydrochloric acid solution; the molar concentration of hydrogen ions in the second acid solution may be 1-4 mol / L, or may also be 2-3 mol / L; the mass ratio of the waste cathode material to the second acid solution may be 1:4-10, specifically 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10. As a specific embodiment of the present invention, the reducing agent may include sodium thiosulfate or hydrogen peroxide; the mass ratio of the waste cathode material to the reducing agent may be 1:0.2-0.5, specifically 1:0.2, 1:0.3, 1:0.4 or 1:0.5. The present invention has no special requirements for the way of mixing the waste cathode material, the second acid solution and the reducing agent, as long as they can be mixed evenly. As a specific embodiment of the present invention, the temperature of the second leaching may be 50-95 °C, or may also be 60-80 °C; the time of the second leaching may be 2-4 h, or may also be 2.5-3 h; the second leaching may be accompanied by stirring, and the rotation speed of the stirring may be 100-400 r / min, or may also be 200-300 r / min.

[0049] Through the second leaching, the present invention can leach out the metal elements in the waste cathode material; the metal elements may include manganese, cobalt, nickel and lithium.

[0050] After obtaining the leaching solution, the present invention performs multi-stage extraction on the leaching solution to obtain a raffinate. As a specific embodiment of the present invention, the multi-stage extraction may include first extraction, second extraction, third extraction and fourth extraction carried out in sequence; the extractant for the first extraction may be P204 extractant, the extractant for the second extraction may be P204 extractant, the extractant for the third extraction may be P507 extractant, and the extractant for the fourth extraction may be P507 extractant. Through the first extraction, the present invention can remove the impurities in the leaching solution, and the impurities include one or more of Fe, Zn, Ca, Al and Cu; through the second extraction, the present invention can separate the manganese element in the leaching solution; through the third extraction, the present invention can separate the cobalt element in the leaching solution; through the fourth extraction, the present invention can separate the nickel element in the leaching solution; the raffinate contains a small amount of lithium element. Through multi-stage extraction, the present invention preferentially extracts impurity ions with P204 and then extracts manganese ions, and then uses P507 to extract cobalt and then nickel. When the concentration of the target ion reaches the requirement, it enters the next extraction stage, so as to realize the fractional extraction of different elements.

[0051] After obtaining the raffinate, the present invention recycles the raffinate to the first leaching. As a specific embodiment of the present invention, the pH value of the raffinate can be 4.5 - 5.0; before recycling the raffinate to the first leaching, it may further include: adjusting the pH value of the raffinate to the pH value required for the first acid solution.

[0052] Figure 1 It is a process schematic diagram of the method for extracting lithium elements from waste batteries provided by the present invention.

[0053] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0054] Example 1

[0055] Step 1: Charge the waste lithium-ion battery at a constant current and voltage of 1C until the current is less than 0.1C and then end.

[0056] Step 2: Put the charged waste battery in step 1 into a crusher and crush it underwater to obtain a slurry.

[0057] Step 3: Put the slurry after crushing in step 2 into a bubble flotation device, stir and mix at 1000 rpm for 10 min, then inject foam with a concentration of 10 ppm. After entering the flotation tank, continue to stir and mix at 1000 rpm for 10 min, and then continuously inject air at a flow rate of 3 L / min for 5 min.

[0058] Step 4: Separate the upper liquid after bubble flotation to obtain waste graphite, and the lower liquid after bubble flotation is a mixed slurry of black powder.

[0059] Step 5: Wash the waste graphite and leach it in a sulfuric acid solution with a hydrogen ion concentration of 2 mol / L at a mass ratio of 1:2 (accompanied by stirring at 200 r / min) for 3 h to obtain a lithium-containing solution.

[0060] Step 6: Filter the mixed slurry obtained in step 4 and carry out high-temperature pyrolysis (calcination) at 700 °C for 2 h to remove organic substances such as binders and plastics.

[0061] Step 7: Obtain waste cathode materials with a particle size < 100 mesh by multi-stage screening of the calcined powder in step 6.

[0062] Step 8: Mix the waste cathode materials separated in step 7, a sulfuric acid solution with a hydrogen ion concentration of 4 mol / , and sodium thiosulfate, and carry out leaching at 60 °C and 200 r / min for 2 h to obtain a leaching solution; the mass ratio of the waste cathode materials to the sulfuric acid solution is 1:4, and the mass ratio of the waste cathode materials to sodium thiosulfate is 1:0.4.

[0063] Step Nine: Perform multi-stage extraction on the leaching solution obtained in Step Eight. Use P204 extractant for the first extraction to remove impurities, and use P204 extractant for the second extraction to remove manganese; use P507 extractant for the third extraction to remove cobalt, and use P507 extractant for the fourth extraction to remove nickel, obtaining a raffinate containing a small amount of residual lithium element; adjust the pH value of the obtained raffinate and reuse it in Step Five as the lithium leaching solution.

[0064] Example 2

[0065] Step One: Charge the used lithium-ion battery at a constant current of 1C until the current is less than 0.1C and then end the charging.

[0066] Step Two: Put the charged used battery obtained in Step One into a crusher and crush it underwater to obtain a slurry.

[0067] Step Three: Put the slurry obtained after crushing in Step Two into a bubble flotation device, stir and mix it at 500 rpm for 15 min, then inject foam with a concentration of 8 ppm, continue to stir and mix it at 500 rpm in the flotation cell for 5 min after entering the flotation cell, and then continuously inject air at a flow rate of 4 L / min for 5 min.

[0068] Step Four: Separate the upper liquid after bubble flotation to obtain used graphite, and the lower liquid after bubble flotation is a mixed slurry of black powder.

[0069] Step Five: Wash the used graphite and leach it in a hydrochloric acid solution with a hydrogen ion concentration of 3 mol / L at a mass ratio of 1:3 (with stirring at 100 r / min) for 3 h to obtain a lithium-containing solution.

[0070] Step Six: Filter the mixed slurry obtained in Step Four and perform high-temperature pyrolysis (calcination) at 700 °C for 2 h to remove organic substances such as binders and plastics.

[0071] Step Seven: Obtain the used cathode material with a particle size of less than 100 mesh by multi-stage screening of the calcined powder in Step Six.

[0072] Step Eight: Mix the used cathode material separated in Step Seven, hydrochloric acid solution with a hydrogen ion concentration of 3 mol / , and hydrogen peroxide, and perform leaching at 65 °C and 100 r / min for 2 h to obtain a leaching solution; the mass ratio of the used cathode material to the hydrochloric acid solution is 1:5, and the mass ratio of the used cathode material to hydrogen peroxide is 1:0.4.

[0073] Step Nine: Perform multi-stage extraction on the leaching solution obtained in Step Eight. Use P204 extractant for the first extraction to remove impurities, and use P204 extractant for the second extraction to remove manganese. Use P507 extractant for the third extraction to remove cobalt, and use P507 extractant for the fourth extraction to remove nickel, obtaining a raffinate containing a small amount of residual lithium element. After adjusting the pH value of the obtained raffinate, reuse it in Step Five as the lithium leaching solution.

[0074] Example 3

[0075] Step One: Charge the used lithium-ion battery at a constant current of 1C until the current is less than 0.05C and then end the charging.

[0076] Step Two: Put the charged used battery from Step One into a crusher and crush it underwater to obtain a slurry.

[0077] Step Three: Put the slurry after crushing in Step Two into a bubble flotation device, stir and mix at 1000 rpm for 5 min, then introduce foam with a concentration of 10 ppm. After entering the flotation tank, continue to stir and mix at 1000 rpm for 5 min, and then continuously inject air at a flow rate of 2 L / min for 10 min.

[0078] Step Four: Separate the upper liquid after bubble flotation to obtain used graphite, and the lower liquid after bubble flotation is a mixed slurry of black powder.

[0079] Step Five: Wash the used graphite and leach it in a hydrochloric acid solution with a hydrogen ion concentration of 2 mol / L at a mass ratio of 1:3 (with stirring at 300 r / min) for 2 h to obtain a lithium-containing solution.

[0080] Step Six: Filter the mixed slurry obtained in Step Four and perform high-temperature pyrolysis (calcination) at 700 °C for 2 h to remove organic substances such as binders and plastics.

[0081] Step Seven: Obtain used cathode materials with a particle size < 100 mesh by multi-stage screening of the calcined powder in Step Six.

[0082] Step Eight: Mix the used cathode materials separated in Step Seven, a hydrochloric acid solution with a hydrogen ion concentration of 4 mol / , and hydrogen peroxide, and perform leaching at 70 °C and 300 r / min for 3 h to obtain a leaching solution. The mass ratio of the used cathode materials to the hydrochloric acid solution is 1:4, and the mass ratio of the used cathode materials to hydrogen peroxide is 1:0.4.

[0083] Step 9: Perform multi-stage extraction on the leaching solution obtained in Step 8. Use P204 extractant for the first extraction to remove impurities, and use P204 extractant for the second extraction to remove manganese. Use P507 extractant for the third extraction to remove cobalt, and use P507 extractant for the fourth extraction to remove nickel, obtaining a raffinate containing a small amount of residual lithium element. After adjusting the pH value of the obtained raffinate, reuse it in Step 5 as the lithium leaching solution.

[0084] Use an inductively coupled plasma optical emission spectrometer (ICP-OES) to detect the concentrations of various elements in the lithium-containing solution obtained in Step 5 during the purification and separation process of Examples 1 to 3. The results are listed in Table 1.

[0085] Table 1 Concentrations of various elements in the lithium-containing solution obtained in Step 5 of Examples 1 to 3

[0086]

[0087] Use ICP-OES to measure the contents of various elements in the lithium-containing solution in Step 5 and the extraction solution obtained in Step 9 of Examples 1 to 3, and then calculate the leaching rates of lithium, nickel, cobalt, and manganese in the waste lithium batteries after purification and separation. The results are listed in Table 2.

[0088] Table 2 Leaching rates of various elements in the waste batteries after being treated with Examples 1 to 3

[0089]

[0090] It can be seen from the results of Table 1 and Table 2 that the method provided by the present invention can leach out most of the metal elements in the waste batteries, and the recovery rates are relatively high, all above 95%.

[0091] Although the above embodiments have made a detailed description of the present invention, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for extracting lithium from waste batteries, characterized in that: The following steps are involved: The waste lithium-ion batteries are charged and then crushed underwater to obtain slurry; The slurry is subjected to bubble flotation to obtain waste graphite and mixed slurry respectively; the bubble flotation comprises the following steps: placing the slurry in a flotation device, stirring it for the first time, introducing foam, stirring it for the second time after entering the flotation tank, and introducing air; the speed of the first stirring is 500-1500rpm, and the time of the first stirring is 5-30min; the concentration of foam in the system after the foam is introduced is 5-20ppm; the speed of the second stirring is 500-1500rpm, and the time of the second stirring is 5-30min; the flow rate of the air is 1-10L / min, and the time of the air is 4-6min; The waste graphite is subjected to a first leaching in a first acid solution to obtain a lithium-containing solution; The mixed slurry is calcined and then sieved, and the sieved material is taken to obtain the waste positive electrode material; The waste positive electrode material, the second acid solution and the reducing agent are mixed for a second leaching to obtain a leaching solution; the molar concentration of hydrogen ions in the second acid solution is 1-4 mol / L, and the mass ratio of the waste positive electrode material to the second acid solution is 1:4-10; the reducing agent includes sodium thiosulfate or hydrogen peroxide; the mass ratio of the waste positive electrode material to the reducing agent is 1:0.2-0.5; the temperature of the second leaching is 50-95° C., and the time of the second leaching is 2-4 hours; The extract is subjected to multi-stage extraction to obtain a raffinate; The raffinate is recycled to the first leaching.

2. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The charging is to charge the waste lithium-ion battery to saturation.

3. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The molar concentration of hydrogen ions in the first acid solution is 1-4 mol / L, and the mass ratio of the waste graphite to the first acid solution is 1:2-4; The first leaching time is 1-4 hours, the first leaching is accompanied by stirring, and the stirring speed is 100-400 r / min.

4. The method for extracting lithium from waste batteries according to claim 1 or 3, characterized in that: The pH value of the raffinate is 4.5-5.0; Reusing the raffinate for the first leaching step further comprises: adjusting the pH value of the raffinate to a pH value required by the first acid solution.

5. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The calcination temperature is 400-800° C., and the calcination holding time is 1-4 hours.

6. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The screening includes multi-stage screening; the particle size of the waste positive electrode material is less than 100 mesh.

7. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The second leaching is accompanied by stirring, and the stirring speed is 100-400 r / min.

8. The method for extracting lithium from waste batteries according to claim 1, characterized in that: The multi-stage extraction includes a first extraction, a second extraction, a third extraction and a fourth extraction performed sequentially; The first extraction solvent is P204 extraction solvent, the second extraction solvent is P204 extraction solvent, the third extraction solvent is P507 extraction solvent, and the fourth extraction solvent is P507 extraction solvent.

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