Method for comprehensively recycling positive electrode material of waste lithium iron phosphate battery

Abstract

The invention relates to a method for comprehensively recycling a positive electrode material of a waste lithium iron phosphate battery, which comprises the following steps of: (1) discharging the waste lithium iron phosphate battery: providing a power supply by the waste lithium iron phosphate battery, and electrolyzing a lithium precipitation mother solution by using a three-chamber diaphragm electrolytic bath; (2) crushing and sorting; (3) two-stage leaching: leaching the lithium iron phosphate positive electrode powder with a sulfuric acid solution generated by electrolysis of a lithium precipitation mother solution, and adding an aeration disc at the bottom of a reaction kettle for aeration; adding a dilute sulfuric acid solution generated by electrolysis of lithium precipitation mother liquor into first-section leaching residues for leaching; (4) two-stage impurity removal; and (5) preparing lithium carbonate. According to the method, the lithium precipitation mother liquor for the waste lithium iron phosphate battery is discharged to prepare the sulfuric acid and sodium hydroxide-lithium hydroxide mixed solution for production, so that residual electricity is utilized, a production reagent is saved, and the problems of high energy consumption, large lithium loss and poor sale of a byproduct sodium sulfate in evaporative crystallization of sodium sulfate are solved; and the aim of circularly and comprehensively utilizing the waste lithium iron phosphate battery is fulfilled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resource recycling of waste lithium ion batteries, and particularly relates to a comprehensive recovery method for preferentially extracting lithium from a positive electrode material of a waste lithium iron phosphate battery. BACKGROUND

[0002] In recent years, lithium iron phosphate batteries have become one of the mainstream choices for new energy vehicle power batteries due to their high energy density, high safety, long cycle life and cost advantage. However, with the arrival of the battery retirement tide, efficient recovery of waste lithium iron phosphate batteries has become a difficult problem to be solved. At present, the industry generally adopts a wet recovery process, which mainly dissolves lithium, iron and other metals in the pretreated waste lithium iron phosphate positive electrode material by acid leaching, and then recovers lithium by step-by-step precipitation or extraction separation. There are usually two routes for leaching of lithium iron phosphate batteries. One is full element leaching, which leaches lithium and iron in the form of ions, and the other is preferential lithium extraction, which selectively leaches lithium ions, and iron is left in the leaching residue in the form of a precipitate for subsequent processing to prepare phosphoric acid iron or for other purposes. The full element leaching method consumes a large amount of raw materials, has a long process flow, high cost, poor economic benefit and is not environmentally friendly. In contrast, the industrial application of the preferential lithium extraction method has obvious advantages.

[0003] The multi-step leaching acid-base adjustment of the conventional preferential lithium extraction method still has problems of high raw material consumption and low reaction efficiency; the lithium precipitation reaction and the lithium precipitation mother liquor need to be treated to remove carbonate and concentrated and crystallized, resulting in high energy consumption and large equipment investment; a large amount of sodium sulfate is produced by crystallization, which has limited market demand, resulting in accumulation of sodium sulfate waste salt; the reagent consumption is large, and reagents such as sulfuric acid and hydrogen peroxide are purchased in the leaching stage, and alkaline reagents such as sodium hydroxide are used in the impurity removal process, and the treatment cost still needs to be reduced.

[0004] During the disassembly and pretreatment of waste batteries, the charged crushing can easily cause a fire. The existing discharge technology mostly uses external resistance discharge or soaking in a salt solution for discharge, which is time-consuming and inefficient, and cannot utilize the residual electrical energy, resulting in resource waste. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application provides a method for comprehensive recovery of waste lithium iron phosphate batteries, which aims to provide a method for recovering waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0006] Step one, place the waste lithium iron phosphate battery in a three-chamber diaphragm electrolytic cell, discharge, and electrolyze in the middle chamber with lithium precipitation mother liquor, the anode chamber is filled with dilute sulfuric acid solution, and the cathode chamber is filled with dilute sodium hydroxide solution, and the electrolysis is carried out until the residual electricity of the battery is fully discharged.

[0007] Step two, the waste lithium iron phosphate battery after discharge is crushed, and the positive electrode material containing lithium iron phosphate, aluminum, copper and conductive agent is obtained by roasting and sorting;

[0008] Step three, first stage leaching: the positive electrode material is slurried with the second stage leaching liquid, and the dilute sulfuric acid after the anode chamber reaction in step one is added, the leaching temperature is 55-65℃, the pH value is controlled to 1.8-2.3 during the leaching process, oxygen or oxygen-enriched gas is introduced through the aeration disc at the bottom of the reactor, and hydrogen peroxide is added at the same time, the leaching time is 1-3h, the pH value at the end of the leaching is controlled to 3.0-3.5, and the first stage leaching liquid and the first stage leaching residue are obtained by solid-liquid separation;

[0009] Step four, second stage leaching: the first stage leaching residue is slurried with washing water, and the dilute sulfuric acid after the anode chamber reaction in step one is added, the leaching temperature is 55-65℃, the pH value is 1.5-2.0, and the leaching time is 1-3h, and the second stage leaching liquid and the second stage leaching residue are obtained by solid-liquid separation;

[0010] Step five, impurity removal: the first stage leaching liquid is added to the sodium hydroxide-lithium hydroxide mixed solution after the cathode chamber reaction in step one, the pH value is adjusted to 4.5-7.0, the reaction time is 1-3h, and the filter residue is removed by solid-liquid separation; the sodium hydroxide-lithium hydroxide mixed solution after the cathode chamber reaction in step one is continuously added to the first stage impurity removal filtrate, and sodium carbonate is added, the pH value is adjusted to 12.0-13.0, the reaction time is 1-3h, and the filter residue is removed by solid-liquid separation.

[0011] Step six, lithium precipitation: the impurity-removed solution is added to a lithium precipitation kettle, and a sodium carbonate solution is added for high-temperature lithium precipitation, then the precipitate is centrifuged and washed with pure water and dried to obtain lithium carbonate product.

[0012] Preferably, the washing water or the second stage leaching liquid of the leaching residue is used as the anode liquid in the anode chamber in step one, and the washing water after impurity removal or the lithium carbonate washing water is used as the cathode liquid in the cathode chamber.

[0013] Preferably, in step three, the aeration gas source for the first stage leaching is oxygen generated in the electrolysis process or oxygen-enriched nitrogen generated in the pretreatment stage.

[0014] Preferably, in step five, the impurity removal reaction temperature is 60-70℃.

[0015] Preferably, in step five, the solid-liquid separation adopts precision filtration, and the filter membrane pore size is ≤0.45μm, so that the concentration of suspended solids in the filtrate is ≤10ppm.

[0016] Preferably, in step six, the concentration of sodium carbonate is 300-350g / L, and the precipitation time is 50-80min.

[0017] Preferably, the sodium carbonate solution in step six is added in a pulse injection manner, and the pulse frequency is 5-10 times / min.

[0018] The method has the following advantages: the discharge of the waste battery is electrolytic discharge using the lithium precipitation mother liquor and the residual electricity of the battery, the acid for leaching and the alkali for impurity removal are generated synchronously, the reagent recycling is realized, and the recovery treatment cost is greatly reduced; in the aeration oxidation stage, the oxygen gas is aerated by using the electrolysis byproduct oxygen gas or nitrogen-rich oxygen gas, the gas flow is appropriately controlled, and the hydrogen peroxide is added, so that the hydrogen peroxide addition amount is significantly reduced compared with the traditional process; the sodium sulfate mother liquor product participates in the electrolytic discharge of the waste battery, and the problem of sodium sulfate waste salt accumulation is improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The waste lithium iron phosphate battery positive material comprehensive recovery process flowchart of the application. DETAILED DESCRIPTION

[0020] First, the discharge treatment of the waste lithium iron phosphate battery is performed, a three-chamber diaphragm electrolytic cell is made, which is divided into a cathode chamber, an anode chamber by an anion exchange membrane and a cation exchange membrane, the anode chamber is filled with leaching residue washing water or two-stage leaching liquid as an anode liquid, the cathode chamber is filled with impurity removal washing water or lithium carbonate washing water as a cathode liquid, the electrode uses graphite, the lithium precipitation mother liquor generated in the production process of the lithium iron phosphate battery is collected as an electrolyte, the electrode is installed, the positive and negative electrodes of the waste lithium iron phosphate battery are connected to the anode and cathode of the electrolytic cell by wires, electrolysis is performed at normal temperature, dilute sulfuric acid solution is generated in the anode chamber, and sodium hydroxide-lithium hydroxide mixed solution is generated in the cathode chamber. When the concentration of the sodium sulfate solution in the electrolytic cell is lower than 0.1 mol / L, it is replaced, and when the concentrations of sulfuric acid and sodium hydroxide reach about 15%, new washing water is replaced. After electrolysis, the sodium sulfate and lithium sulfate mixed solution returns to the first-stage leaching, and the lithium precipitation mother liquor is supplemented or replaced according to the electrolysis condition. When the discharge potential of the waste lithium ion battery is low, the series-parallel connection mode can be used to increase the current and maintain the voltage ≥2V, so as to fully utilize the residual electricity, improve the electrolysis speed, and try to discharge the residual electricity in the waste lithium ion battery

[0021] After electrolytic discharge, the waste battery enters the pretreatment stage, is crushed, ball milled, and roasted, and the positive electrode powder containing 0.1-0.8% of copper and 0.1-0.8% of aluminum is sorted out.

[0022] Example 1

[0023] The sorted lithium iron phosphate positive electrode powder 500 g is slurried with 2.5 L of the secondary leaching solution, and then 500 mL of the sulfuric acid solution prepared by electrolysis of the lithium precipitation mother liquor is added to carry out leaching, one-stage leaching is carried out, acid is added to control the pH value to be 1.8-2.3, the leaching temperature is 55 ℃, the leaching time is 1 h, aeration is started, the aeration disc is installed below the stirring paddle at the bottom of the one-stage leaching reactor, 100 mL of hydrogen peroxide is added at the same time, the reaction time is 1 h, the end point pH value is 3.0, after the leaching is completed, solid-liquid separation is carried out, and one-stage leaching solution and one-stage leaching residue are obtained; the one-stage leaching residue is slurried with washing water, 90 mL of the dilute sulfuric acid solution generated in the discharging process is added, the pH value is adjusted to about 1.5, secondary leaching is carried out, the leaching time is 1 h, after the leaching is completed, solid-liquid separation is carried out, and secondary leaching solution and secondary leaching residue are obtained, and the secondary leaching solution is returned to the one-stage leaching.

[0024] The one-stage leaching solution is adjusted to a pH value of 4.5 by adding the mixed sodium hydroxide-lithium hydroxide solution prepared by electrolysis of the lithium precipitation mother liquor, and the reaction time is 2 h, after filtration, one-stage impurity removal filtrate and one-stage impurity removal residue are obtained. The one-stage impurity removal filtrate is continuously adjusted to a pH value of 12.5 by adding the mixed sodium hydroxide-lithium hydroxide solution prepared by electrolysis of the lithium precipitation mother liquor, and 2 g of sodium carbonate is added at the same time, the impurity removal reaction time is 1 h, the impurity removal process temperature is 60-70 ℃, and solid-liquid separation is carried out, and the solution after secondary impurity removal is obtained.

[0025] The solution after secondary impurity removal is subjected to lithium precipitation, the concentration of the sodium carbonate solution is 300 g / L, the pulse frequency is 8 times / min, the precipitation reaction time is 60 min, and after centrifugal separation, the obtained Li2CO3-D3 is washed with pure water and dried, and finally the Li2CO3-D3 meeting the requirements of the battery grade product standard is obtained, and the purity is ≥99.8 %.

[0026] Example 2

[0027] The sorted waste lithium iron phosphate positive electrode powder 1 t is added to 2 m 3 The secondary leaching solution is slurried, and then 1 m 3 L of the sulfuric acid solution prepared by electrolysis of the lithium precipitation mother liquor is added to carry out leaching, one-stage leaching is carried out, acid is added to control the pH value to be 1.8-2.3, the leaching temperature is 60 ℃, the leaching time is 2 h, aeration is started after the leaching for 2 h, 200 L of hydrogen peroxide is added at the same time, the reaction time is 2 h, the end point pH value is 3.5, after the leaching is completed, solid-liquid separation is carried out, and one-stage leaching solution and one-stage leaching residue are obtained; wherein, the aeration disc is installed below the stirring paddle at the bottom of the one-stage leaching reactor, and the oxygen utilization rate is improved. The one-stage leaching residue is slurried with washing water, 150 mL of the sulfuric acid solution prepared by electrolysis of the lithium precipitation mother liquor is added to control the pH value to be about 1.7, secondary leaching is carried out, the leaching time is 2 h, after the leaching is completed, solid-liquid separation is carried out, and secondary leaching solution and secondary leaching residue are obtained, and the secondary leaching solution is returned to the one-stage leaching.

[0028] The pH value of the sodium hydroxide-lithium hydroxide mixed solution prepared by electrolysis of the lithium precipitation mother liquor added to the first-stage leaching solution is adjusted to 6.0, and the reaction time is 2 h. After filtration, a first-stage impurity removal filtrate and a first-stage impurity removal residue are obtained. The first-stage impurity removal filtrate is continuously added with the sodium hydroxide-lithium hydroxide mixed solution prepared by electrolysis of the lithium precipitation mother liquor, and the pH value is adjusted to 13.0. Meanwhile, 30 g of sodium carbonate is added. The impurity removal reaction time is 2 h, and the impurity removal process temperature is 60-70°C. Solid-liquid separation is performed to obtain a second-stage impurity removal solution.

[0029] After the second-stage impurity removal, lithium precipitation is performed. At 90°C, a sodium carbonate solution with a concentration of 330 g / L is added in a pulse form. The pulse frequency is 5 times / min, and the precipitation reaction time is 50 min. After centrifugal separation, washing and drying are performed with pure water. Finally, Li2CO3-D3 that meets the requirements of the battery-grade product standard is obtained, with a purity of ≥99.75%.

[0030] Example 3

[0031] The sorted waste lithium iron phosphate positive electrode powder 3 t is added with the second-stage leaching solution 6 m 3 , and the sulfuric acid solution prepared by electrolysis of the lithium precipitation mother liquor 3 m 3 . First-stage leaching is performed. The pH value is controlled at 1.8-2.3. The leaching temperature is 65°C. After leaching for 3 h, aeration is started. Meanwhile, 600 L of hydrogen peroxide is added. The reaction time is 3 h. The terminal pH value is 3.5. After the completion of leaching, solid-liquid separation is performed to obtain a first-stage leaching solution and a first-stage leaching residue. The aeration disc is installed below the stirring paddle at the bottom of the first-stage leaching reactor to improve oxygen utilization. The first-stage leaching residue is slurried with the sulfuric acid solution prepared by electrolysis of the lithium precipitation mother liquor 440 mL. The pH value is controlled at about 2.0 to perform second-stage leaching. The leaching time is 3 h. After the completion of leaching, solid-liquid separation is performed to obtain a second-stage leaching solution and a second-stage leaching residue. The second-stage leaching solution is returned to the first-stage leaching as the slurry water phase.

[0032] The pH value of the sodium hydroxide-lithium hydroxide mixed solution prepared by electrolysis of the lithium precipitation mother liquor added to the first-stage leaching solution is adjusted to 7.0, and the reaction time is 2 h. After filtration, a first-stage impurity removal filtrate and a first-stage impurity removal residue are obtained. The first-stage impurity removal filtrate is continuously added with the sodium hydroxide-lithium hydroxide mixed solution prepared by electrolysis of the lithium precipitation mother liquor, and the pH value is adjusted to 12.0. 100 g of sodium carbonate is weighed, dissolved in water, and then added to the reactor. The impurity removal reaction time is 3 h, and the impurity removal process temperature is 60-70°C. Solid-liquid separation is performed to obtain a second-stage impurity removal solution.

[0033] After the second-stage impurity removal, lithium precipitation is performed. At 90°C, a sodium carbonate solution with a concentration of 350 g / L is added in a pulse form. The pulse frequency is 10 times / min, and the precipitation reaction time is 80 min. After centrifugal separation, washing and drying are performed with pure water. Finally, Li2CO3-D3 that meets the requirements of the battery-grade product standard is obtained, with a purity of ≥99.76%.

[0034] The chemical composition detection results of lithium carbonate recovered by the embodiments 1 to 3 of the present application and the chemical composition ratio comparison results of Li2CO3-D3 specified in the industry standard YS / T 582-2023 "Battery-grade lithium carbonate" are shown in Table 1, and the use requirements of the battery-grade lithium carbonate product can be met.

[0035] Table 1

[0036]

[0037]

[0038] The method for recycling positive electrode powder of waste lithium iron phosphate battery by using residual power and lithium precipitation mother liquor electrolysis of waste lithium ion battery provided by the present application has low cost, simple process, high valuable metal recovery rate, and good economic and social benefits. The method of the present application can also be used for recycling of waste nickel-cobalt-manganese ternary lithium ion battery.

[0039] The above is the preferred embodiment of the present application, and any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application falls within the protection scope of the present application.

Claims

1. A method for comprehensive recovery of waste lithium iron phosphate battery positive electrode material, characterized in that, The application relates to a lithium phosphate iron battery recycling method. Step one: placing waste lithium phosphate iron batteries in a three-chamber diaphragm electrolytic cell, discharging, placing lithium sink mother liquor in the middle chamber, placing dilute sulfuric acid solution in the anode chamber, placing dilute sodium hydroxide solution in the cathode chamber, and electrolyzing until the residual electricity of the batteries is fully released; Step two: crushing the discharged waste lithium phosphate iron batteries, roasting and sorting, and obtaining positive electrode materials containing lithium phosphate iron, aluminum, copper and conductive agents; Step three: one-stage leaching: slurryizing the positive electrode materials and two-stage leaching liquid, adding dilute sulfuric acid reacted in the anode chamber in step one, controlling the leaching temperature to be 55-65 DEG C, controlling the pH value in the leaching process to be 1.8-2.3, introducing oxygen or oxygen-rich gas through the aeration disc at the bottom of the reactor, simultaneously adding hydrogen peroxide, leaching for 1-3 hours, controlling the pH value at the leaching end point to be 3.0-3.5, and performing solid-liquid separation to obtain one-stage leaching liquid and one-stage leaching residue; Step four: two-stage leaching: slurryizing the one-stage leaching residue and washing water, adding dilute sulfuric acid reacted in the anode chamber in step one, controlling the leaching temperature to be 55-65 DEG C, controlling the leaching pH value to be 1.5-2.0, and performing solid-liquid separation after leaching for 1-3 hours to obtain two-stage leaching liquid and two-stage leaching residue; Step five: impurity removal: adding the one-stage leaching liquid into the sodium hydroxide-lithium hydroxide mixed solution reacted in the cathode chamber in step one, adjusting the pH value to be 4.5-7.0, performing solid-liquid separation after reacting for 1-3 hours to remove the filter residue; continuously adding the sodium hydroxide-lithium hydroxide mixed solution reacted in the cathode chamber in step one into the one-stage impurity removal filtrate, adding sodium carbonate, adjusting the pH value to be 12.0-13.0, and performing solid-liquid separation after reacting for 1-3 hours to remove the filter residue; Step six: lithium sinking: adding the impurity-removed solution into a lithium sinking reactor, adding sodium carbonate solution to sink lithium at high temperature, centrifugally separating the precipitate, washing and drying the precipitate with pure water, and obtaining lithium carbonate products.

2. The method of claim 1, wherein: The washing water or two-stage leaching liquid of the leaching residue is used as the anode liquid in the anode chamber in step one, and the washing water after impurity removal or lithium carbonate washing water is used as the cathode liquid in the cathode chamber.

3. The method of claim 1, wherein: In step three, the aeration gas source of the one-stage leaching is oxygen generated in the electrolysis process or oxygen-rich gas generated in the nitrogen gas preparation in the pretreatment stage.

4. The method of claim 1, wherein: In step five, the impurity removal reaction temperature is 60-70 DEG C.

5. The method of claim 1, wherein: In step five, the solid-liquid separation adopts precision filtration, the filter membrane aperture is less than or equal to 0.45 microns, and the concentration of the suspended matter in the filtrate is less than or equal to 10 ppm.

6. The method of claim 1, wherein: In step six, the concentration of the sodium carbonate solution is 300-350 g / L, and the precipitation time is 50-80 minutes.

7. The method of claim 6, wherein, In step six, the sodium carbonate solution is added in a pulse injection mode, and the pulse frequency is 5-10 times per minute.

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