Method for selectively separating and recycling lithium in retired lithium iron phosphate battery electrode through cooperation of sulfate and sulphide salt

Abstract

The invention relates to a method for selectively separating and recycling lithium in a decommissioned lithium iron phosphate battery electrode through cooperation of sulfate and sulphide salt, and belongs to the field of new energy material recycling. The method comprises the following steps: adding the retired lithium iron phosphate battery electrode into a sulfate-sulfide salt system, fully and uniformly mixing to obtain a mixture, and performing microwave roasting on the mixture to obtain a microwave roasting product (Li2SO4 / FePO4); and adding the microwave roasting product into a water-based system, introducing an ultrasonic external field to carry out selective water leaching, and carrying out solid-liquid separation to obtain FePO4 filter residues and a Li2SO4 solution. According to the invention, sulfate and sulfide salt are cooperated for microwave roasting, so that rapid selective heating of materials can be realized, phase conversion of LiFePO4 to Li2SO4 (water-soluble) and FePO4 (indissolvable) is promoted, a water-soluble phase and an indissolvable substance of a microwave roasting product are efficiently stripped through ultrasonic waves, wrapping of conductive carbon, a binder, an organic electrolyte and the like is prevented, an effective reaction contact area is increased, lithium ions are desorbed, and the lithium ion battery performance is improved. And selective separation and recovery of Li2SO4 and FePO4 are realized.

Description

Technical Field

[0001] The present invention relates to a method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by using sulfate in combination with sulfide, and belongs to the field of new energy material recovery. Background Art

[0002] LiFePO4 batteries are widely used in new energy vehicles, starting power supplies, energy storage, etc. due to their advantages such as good theoretical safety, low energy density, and long service life. The usage of LiFePO4 batteries is increasing significantly. Therefore, the recycling and reuse of waste LiFePO4 batteries are particularly important. The current methods for recycling / regenerating LiFePO4 mainly include regeneration and repair methods and wet dissolution and extraction methods. The regeneration and repair methods mainly include wet regeneration and repair, high-temperature direct repair, and lithium supplementation roasting repair. Although the regeneration and repair technology does not damage the LiFePO4 structure, impurities such as copper and aluminum will have a negative impact on the electrochemical performance of the repaired material, and this method has extremely high requirements for material purity and cost, so it has not been widely used; wet dissolution and extraction is a common recycling technology at present. Among them, the full dissolution and extraction technology completely destroys the LiFePO4 crystal structure through acid leaching reaction, so that Fe 2+ , Li + completely enter the solution, and then stepwise impurity removal and lithium precipitation are carried out. However, this method still has problems such as poor lithium leaching effect and low recovery rate of iron phosphate (FePO4), and it is difficult to achieve the purpose of selective separation and recovery of lithium / iron. Therefore, it is of practical significance to develop a short-process, high-efficiency LiFePO4 treatment process suitable for industrial production. Summary of the Invention

[0003] Aiming at the problems of high energy consumption, low recovery rate, complex process, and large amount of waste liquid in the existing roasting-acid leaching-purification-lithium precipitation process, the present invention proposes a method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by using sulfate in combination with sulfide. The microwave roasting of sulfate in combination with sulfide can realize rapid selective heating of materials, promote the phase transformation of LiFePO4 into Li2SO4 (water-soluble) and FePO4 (insoluble), and then use the ultrasonic external field not only to efficiently peel off the water-soluble phase and insoluble substances in the microwave roasting product (Li2SO4 / FePO4), increase the effective reaction contact area, promote the floating of organic carbon, and at the same time desorb the attached Li + ; it can also prevent the influence of the wrapping and adsorption behaviors of conductive carbon, binder, organic electrolyte, etc. on the lithium recovery rate; thus realizing the selective separation and recovery of Li2SO4 and FePO4.

[0004] A method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by using sulfate in combination with sulfide, the specific steps are as follows: (1) Add the retired lithium iron phosphate battery electrodes to the sulfate-sulfide system and mix well to obtain a mixture. The mixture is calcined by microwave to obtain a calcined product (Li2SO4 / FePO4). (2) Add the microwave-calcined product to the water leaching system, introduce ultrasonic waves for selective water leaching, and perform solid-liquid separation to obtain FePO4 filter residue and Li2SO4 solution.

[0005] By mass percentage, the retired lithium iron phosphate battery electrodes in step (1) contain 4-5% Li and 32-33% Fe.

[0006] Preferably, in step (1), the sulfate is FeSO4 and the sulfide is FeS.

[0007] Preferably, the mass ratio of the retired lithium iron phosphate battery electrodes to the sulfate and the sulfide in step (1) is 1:1:1.5-2.

[0008] Preferably, in step (1), the microwave calcination temperature is 200-450 °C and the time is 1-5 h.

[0009] Preferably, in step (2), the liquid-solid ratio of the water leaching system to the microwave-calcined product is 8-16 mL:g.

[0010] Preferably, in step (2), the ultrasonic power is 100-600 W.

[0011] Preferably, in step (2), the temperature of the selective water leaching is 30-70 °C and the water leaching time is 75-100 min.

[0012] In the present invention, water is used as the leaching agent, and the lithium leaching rate can be as high as 92.5%, and the FePO4 recovery rate can reach 90.2%.

[0013] The beneficial effects of the present invention are as follows: (1) In the present invention, the microwave calcination of sulfate and sulfide synergistically promotes the phase transformation of LiFePO4 into Li2SO4 (water-soluble) and FePO4 (insoluble). (2) The present invention can realize the high-value utilization of failed lithium iron phosphate (LiFePO4). By ultrasonic high-efficiency stripping of the water-soluble phase and insoluble substances in the microwave-calcined product (Li2SO4 / FePO4), the effective contact area is increased, and the attached Li is desorbed. + ; (3) In the present invention, only water is used as the leaching agent. Li2SO4 (water-soluble) and FePO4 (insoluble) can be separated in 75 min of leaching time. The ultrasonic action can dissociate the agglomerated packages formed by conductive carbon, binder, organic electrolyte, etc. (4) Compared with the conventional complex process with high temperature, high acid, and low daily processing capacity, the present invention uses microwave roasting of sulfate synergistic sulfide - ultrasonic selective water leaching for retired LiFePO4 battery electrodes, which has the advantages of short process, low energy consumption, strong selectivity, high efficiency, and less waste liquid. At a temperature of 30 °C, leaching for 75 minutes can achieve a lithium leaching rate as high as 92.5%, and the FePO4 recovery rate can reach 90.2%. Specific Embodiments

[0014] The following further elaborates on the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the described content.

[0015] Example 1: The main components of the retired lithium iron phosphate battery electrode in this example are shown in Table 1: Table 1 Main components of the retired lithium iron phosphate battery electrode (mass percentage) Li Fe C P 4.43 32.78 3.85 18.79 A method for selectively separating and recovering lithium from retired lithium iron phosphate battery electrodes by sulfate synergistic sulfide, the specific steps are as follows: (1) Add the retired lithium iron phosphate battery electrode into a sulfate - sulfide (FeSO4 - FeS) system and mix well to obtain a mixture. The mixture is subjected to microwave (microwave roasting temperature 400 °C, time 4 h) to obtain a roasted product (Li2SO4 / FePO4); the mass ratio of the retired lithium iron phosphate battery electrode to sulfate and sulfide is 1:1:2; (2) Add the microwave - roasted product into water, introduce ultrasonic waves (180 W), and perform ultrasonic selective water leaching at a temperature of 30 °C for 75 minutes, and then perform solid - liquid separation to obtain FePO4 filter residue and Li2SO4 solution; the liquid - solid ratio mL:g of the aqueous system to the microwave - roasted product is 8:1; After detection, the lithium leaching rate in this example is 92.5%, and the FePO4 recovery rate is 90.2%.

[0016] Example 2: The main components of the retired lithium iron phosphate battery electrode in this example are shown in Table 2: Table 2 Main components of the retired lithium iron phosphate battery electrode (mass percentage) Li Fe C P 4.54 32.38 4.55 20.12 A method for selectively separating and recovering lithium from retired lithium iron phosphate battery electrodes by sulfate synergistic sulfide, the specific steps are as follows: (1) Add the retired lithium iron phosphate battery electrode into a sulfate - sulfide (FeSO4 - FeS) system and mix well to obtain a mixture. The mixture is subjected to microwave (microwave roasting temperature 450 °C, time 5 h) to obtain a roasted product (Li2SO4 / FePO4); the mass ratio of the retired lithium iron phosphate battery electrode to sulfate and sulfide is 1:1:1.8; (2) Add the microwave calcination product into water, introduce ultrasonic wave (250 W), and perform ultrasonic selective water leaching at 50 °C for 95 min. After solid-liquid separation, obtain FePO4 filter residue and Li2SO4 solution; the liquid-solid ratio of the aqueous system to the microwave calcination product is mL:g = 10:1; After detection, the lithium leaching rate in this example is 88.7%, and the FePO4 yield is 75.4%.

[0017] Example 3: The main components of the retired lithium iron phosphate battery electrode in this example are shown in Table 3: Table 3 Main components of the retired lithium iron phosphate battery electrode (mass percentage) Li Fe C P 4.35 32.25 5.45 22.12 A method for selectively separating and recovering lithium from the electrodes of retired lithium iron phosphate batteries by sulfate synergistic sulfide, the specific steps are as follows: (1) Add the retired lithium iron phosphate battery electrode into the sulfate-sulfide (FeSO4-FeS) system and mix well to obtain a mixture. The mixture is calcined by microwave (microwave calcination temperature 300 °C, time 5 h) to obtain a calcination product (Li2SO4 / FePO4); the mass ratio of the retired lithium iron phosphate battery electrode to the sulfate and sulfide is 1:1:1.5; (2) Add the microwave calcination product into water, introduce ultrasonic wave (200 W), and perform ultrasonic selective water leaching at 70 °C for 100 min. After solid-liquid separation, obtain FePO4 filter residue and Li2SO solution; the liquid-solid ratio of the aqueous system to the microwave calcination product is mL:g = 12:1; After detection, the lithium leaching rate in this example is 89.8%, and the FePO4 yield is 73.2%.

[0018] Example 4: The main components of the retired lithium iron phosphate battery electrode in this example are the same as those in Example 3: A method for selectively separating and recovering lithium from the electrodes of retired lithium iron phosphate batteries by sulfate synergistic sulfide, the specific steps are as follows: (1) Add the retired lithium iron phosphate battery electrode into the sulfate-sulfide (FeSO4-FeS) system and mix well to obtain a mixture. The mixture is calcined by microwave (microwave calcination temperature 400 °C, time 3 h) to obtain a calcination product (Li2SO4 / FePO4); the mass ratio of the retired lithium iron phosphate battery electrode to the sulfate and sulfide is 1:1:1.9; (2) Add the microwave calcination product into the aqueous system, introduce ultrasonic wave (300 W), and perform ultrasonic selective water leaching at 70 °C for 85 min. After solid-liquid separation, obtain FePO4 filter residue and Li2SO4 solution; the liquid-solid ratio of the aqueous system to the microwave calcination product is mL:g = 14:1; After detection, the lithium leaching rate in this embodiment is 90.8%, and the yield of FePO4 is 78.7%.

[0019] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate and sulfide synergistically, characterized in that, The specific steps are as follows: (1) Add the electrodes of retired lithium iron phosphate batteries into a sulfate-sulfide system and mix well to obtain a mixture, and the mixture is calcined by microwave to obtain a calcination product; (2) Add the microwave calcination product into a water leaching system, introduce ultrasonic waves for selective water leaching, and perform solid-liquid separation to obtain FePO4 filter residue and Li2SO4 solution.

2. The method for selectively separating and recovering lithium from the electrodes of retired lithium iron phosphate batteries by sulfate in cooperation with sulfide according to claim 1, wherein: By mass percentage, the retired lithium iron phosphate battery electrodes in step (1) contain 4-5% Li and 32-33% Fe.

3. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate in cooperation with sulfide according to claim 1, characterized in that: In step (1), the sulfate is FeSO4 and the sulfide is FeS.

4. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate and sulfide collaboration according to claim 1 or 3, characterized in that: In step (1), the mass ratio of the retired lithium iron phosphate battery electrodes to the sulfate and the sulfide is 1:1:1.5-2.

5. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate in cooperation with sulfide according to claim 1, characterized in that: In step (1), the microwave calcination temperature is 200-450 °C and the time is 1-5 h.

6. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate in cooperation with sulfide according to claim 1, wherein: In step (2), the liquid-solid ratio of the water leaching system to the microwave calcination product is mL:g = 8-16:

1.

7. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by sulfate and sulfide in combination according to claim 1, wherein: In step (2), the ultrasonic power is 100-600 W.

8. The method for selectively separating and recovering lithium in the electrodes of retired lithium iron phosphate batteries by the synergistic effect of sulfate and sulfide according to claim 1, wherein: In step (2), the temperature of selective water leaching is 30-70 °C and the water leaching time is 75-100 min.