A method for pre-extracting lithium from a waste lithium iron phosphate battery positive electrode material and recycling

Abstract

The application belongs to the field of waste battery material recycling, and particularly relates to a recycling method of waste lithium iron phosphate positive material, which comprises the following steps: mixing the waste lithium iron phosphate positive material with a combined treatment agent, calcining the mixture at a temperature above 600 DEG C, and then performing alkali leaching treatment on the calcined material to separate lithium alkali leaching liquid and iron phosphorus residue. The combined treatment agent comprises A component and B component, wherein the A component comprises at least one of FeO, Fe3O4 and Cu2O, and the B component comprises at least one of CaF2, Al2O3 and SiO2. The process can effectively realize the pre-extraction of lithium, and is also conducive to obtaining fine-grained and high-surface free energy iron phosphate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of battery waste recycling, and particularly relates to the field of waste lithium iron phosphate battery material recycling. BACKGROUND

[0002] Currently, there are mainly lithium cobalt oxide batteries (LCO), nickel cobalt manganese batteries (NCM), lithium iron phosphate (LFP) and lithium manganese oxide (LMO) on the market. The prosperity of the market brings huge opportunities, but also potential problems. Obviously, the large resource consumption of lithium, cobalt, nickel, manganese and other metals makes the manufacturing of lithium ion batteries face the dilemma of resource depletion. The content of precious metal resources in waste lithium ion batteries is much higher than that in natural ores. The recycling of metal elements in waste lithium ion batteries has become an important way to alleviate the resource depletion situation and develop industrial circular economy. In addition, the large accumulation of waste lithium ion batteries will also cause potential pollution to the ecological system, as people underestimate the safety hazards such as fire and explosion that waste lithium ion batteries may cause. The recycling of waste batteries can effectively reduce the negative impact on the environment. Therefore, it is imminent to realize the recycling of waste lithium ion batteries. As an important metal, lithium urgently needs to develop new technologies for recycling.

[0003] For the recovery of lithium, the main idea of the prior art is to preferentially extract lithium or extract it together with other elements. Among them, the idea of preferentially extracting lithium can reduce the process loss of lithium and better realize the recovery of lithium.

[0004] Some lithium extraction technologies for lithium iron phosphate are also disclosed in the prior art. For example, the patent document with publication number JP7393608B2 discloses a comprehensive recycling of waste lithium iron phosphate batteries, specifically discloses the realization of preferential lithium extraction by adding solid sodium chlorate. The Chinese patent document with publication number CN117165767A discloses a method for directly mineralizing lithium extraction under sunlight using waste lithium battery positive electrode material. The Chinese patent document with publication number CN116581415A discloses a method for full-element combined recovery of waste phosphorus-iron slag produced by selective lithium extraction of waste lithium iron phosphate and waste lithium cobalt oxide, specifically discloses that the strong oxidizing property of trivalent cobalt ions in lithium cobalt oxide is used to oxidize divalent iron ions in lithium iron phosphate to trivalent, and the reducing property of ferrous ions in lithium iron phosphate is used to reduce trivalent cobalt ions in lithium cobalt oxide to divalent cobalt ions, without adding reducing agents or oxidizing agents, the full-element combined recovery of lithium, cobalt, iron and phosphorus in waste lithium iron phosphate and waste lithium cobalt oxide can be completed.

[0005] Although the prior art can well solve the problem of preferential lithium extraction, the extraction efficiency and effect still need to be improved. Not only that, but the particle size distribution and activity of the obtained FePO4 also need to be improved. SUMMARY

[0006] Aiming at the problems existing in the recovery of waste lithium iron phosphate positive electrode material, the present application aims to provide a waste lithium iron phosphate positive electrode material recovery method, aiming to improve the pre-lithium efficiency and effect of lithium iron phosphate, and co-produce high-quality iron phosphate slag.

[0007] A waste lithium iron phosphate positive electrode material recovery method, waste lithium iron phosphate positive electrode material and combined treatment agent are mixed and calcined at a temperature above 600 DEG C, and then the calcined material is subjected to alkali leaching treatment, obtaining lithium alkali leaching liquid and iron phosphate slag;

[0008] The combined treatment agent comprises A component and B component, wherein the A component comprises at least one of FeO, Fe3O4 and Cu2O; the B component comprises at least one of CaF2, Al2O3 and SiO2.

[0009] The present application innovatively uses a combined treatment agent and waste lithium iron phosphate positive electrode material for batching, so that the transformation of the crystal structure of lithium iron phosphate can be realized based on the lattice oxygen of the molten state conduction, thereby improving the lithium extraction effect, and in addition, high-quality iron phosphate with finer particle size, more uniform particle size distribution and higher surface activation energy can be co-produced.

[0010] In the present application, the lithium iron phosphate positive electrode material is an electrode material obtained by stripping the positive electrode of a waste lithium iron phosphate battery;

[0011] In the present application, the content of lithium iron phosphate active material in the lithium iron phosphate positive electrode material is not particularly required, and considering the economy of the recovery process, it can be above 50wt%, and further can be 70-90wt.%.

[0012] In the present application, at least one of the conductive agent and the binder is allowed to exist in the lithium iron phosphate positive electrode material.

[0013] In the present application, the A component is a composite of FeO and Cu2O; preferably, the weight ratio of FeO to Cu2O is 1:0.5-1.5. Research shows that the use of combined A component can further synergistically improve the lithium extraction effect, and improve the fineness, particle size distribution and surface activation energy of the lithium phosphate slag.

[0014] In the present application, the B component is CaF2. Research shows that the use of CaF2 as the B component can further synergistically improve the lithium extraction effect, and improve the fineness, particle size distribution and surface activation energy of the lithium phosphate slag.

[0015] In the present application, the weight ratio of the A component to the B component is 1:0.1-1, preferably 1:0.2-0.5, and further preferably 1:0.3-0.4.

[0016] In the present application, the weight ratio of lithium iron phosphate in the waste lithium iron phosphate positive material to the A component in the combined treatment agent is 1:1-5, preferably 1:3-4.

[0017] In the present application, the temperature in the calcination stage is 600-950℃, further preferably 800-900℃.

[0018] Preferably, the holding time at the calcination temperature is 2-6h, preferably 3-4h.

[0019] In the present application, the alkali solution in the alkali leaching stage is a solution containing sodium hydroxide and potassium hydroxide.

[0020] Preferably, the concentration of the solute in the alkali solution is 0.5-1M.

[0021] Preferably, the liquid-solid ratio in the alkali leaching process is 20-40mL / g.

[0022] Preferably, the temperature in the alkali leaching stage is below 45℃.

[0023] Preferably, the time in the alkali leaching stage is above 30min, preferably 1-2h.

[0024] In the present application, after the alkali leaching of the calcined material, solid-liquid separation is performed to obtain a lithium leaching solution, and based on conventional means, iron phosphate can be recovered from the alkali leaching residue.

[0025] For example, in an optional scheme of the present application, the alkali leaching residue obtained by alkali leaching is subjected to liquation refining to obtain iron phosphate.

[0026] In the present application, the temperature in the liquation refining stage is 350-500℃, further preferably 380-420℃.

[0027] In the present application, the time for liquation refining is above 1h, further 1.5-4h, and more further 2-3h.

[0028] Advantages

[0029] In the present application, the combined treatment agent and the waste lithium iron phosphate positive material are innovatively used for batching, so that the crystal structure of lithium iron phosphate can be transformed based on the use of lattice oxygen in the molten state, thereby improving the lithium extraction effect, and in addition, high-quality iron phosphate can be co-produced. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in combination with specific embodiments, but the present application is not limited to the following embodiments.

[0031] The waste lithium iron phosphate positive material can be peeled off from the positive electrode of the waste lithium iron phosphate battery based on a conventional process. For example, the steps are as follows: the waste power lithium iron phosphate battery is placed in 2 mol / L brine for 30 h of discharge treatment, the discharged battery is dried at 85°C, the positive electrode sheet is separated, the positive electrode sheet is soaked in N-methyl pyrrolidone, the current collector in the positive electrode sheet is separated, and the waste lithium iron phosphate positive material powder is obtained by filtering, washing and drying, wherein the conductive agent, binder and other components are allowed to be contained, and the content of lithium iron phosphate is between 80-90 wt.%.

[0032] In the present application, the surface free energy can be determined based on conventional methods in the industry, for example, the surface free energy is calculated by testing the contact angle of the particles with water.

[0033] Example 1:

[0034] Step (1): calcination:

[0035] The waste lithium iron phosphate positive material is mixed with a combined treatment agent (which contains A component and B component, wherein the A component is FeO, and the amount of FeO is 3 times the weight of lithium iron phosphate in the waste lithium iron phosphate positive material, and the B component is SiO2, and the weight of SiO2 is 30% of the weight of the A component), and the mixture is placed in a tube furnace, argon is introduced, and calcination is carried out at a temperature of 800°C (calcination temperature) for 5 h to obtain a calcined material;

[0036] Step (2): leaching: an aqueous solution of NaOH with a concentration of 1M is prepared, the calcined material is placed in it and stirred for leaching, the liquid-solid ratio is 30ml / g, the leaching is carried out at room temperature (20-30°C), and the leaching time is 2h, to obtain a lithium metal liquid and a phosphorus-iron slag containing additives, the phosphorus-iron slag is purified by the method of fractional crystallization (temperature is 400°C, time is 2h) to obtain iron phosphate.

[0037] The leaching rate of Li in the leaching solution is 98.2%. The D90 of the particle size of the iron phosphate is 51.6 nm, and the surface free energy is 130 mN / m 2 .

[0038] Example 2

[0039] Compared with Example 1, the only difference is that in step (1), the A component in the combined treatment agent is changed, and the experimental groups are as follows:

[0040] Group A: the A component is Cu2O;

[0041] Group B: the A component is Cu2O and FeO with a weight ratio of 1:1; and in step 2, the concentration of the aqueous sodium hydroxide solution is 0.8M, and the liquid-solid ratio in the alkali leaching stage is 25ml / g;

[0042] Group C: Adjust the weight of component A to 4 times the weight of lithium iron phosphate;

[0043] Other operations and parameters are the same as in Example 1, and the results are as follows:

[0044] Group A: The leaching rate of Li in the leachate was 98.6%. The D90 of iron phosphate was 41.2 nm, and its surface free energy was 133 mN / m². 2 .

[0045] Group B: The leaching rate of Li in the leachate was 98.9%. The D90 of iron phosphate was 33.5 nm, and its surface free energy was 138 mN / m². 2 .

[0046] Group C: The leaching rate of Li in the leachate was 99.2%. The D90 of ferric phosphate was 35.9 nm, and its surface free energy was 135 mN / m². 2 .

[0047] As can be seen from Examples 1 and 2, using the preferred combination of Cu2O and FeO as component A can synergistically improve the leaching efficiency to a certain extent, and improve the fineness and uniformity of particle size distribution of the obtained iron phosphate. Moreover, it can also improve its surface free energy.

[0048] Example 3

[0049] Compared with Example 1, the only difference is that in step (1), component B in the combined treatment agent is changed. Other operations and parameters are the same as in Example 1, and the experimental groups are as follows:

[0050] Group A: Group B consists of CaF2;

[0051] Group B: Group B consists of Al2O3;

[0052] Group C: Component B is 0.4 times the weight of component A;

[0053] All other operations and parameters are the same as in Example 1, and the results are as follows:

[0054] Group A: The leaching rate of Li in the leachate was 99.3%. The D90 of iron phosphate is around 35.3 nm, and its surface free energy is 136 mN / m². 2 .

[0055] Group B: The leaching rate of Li in the leachate was 99.1%. The D90 of iron phosphate was 40.3 nm, and its surface free energy was 132 mN / m². 2 .

[0056] Group C: The leaching rate of Li in the leachate was 99.4%. The D90 of iron phosphate was 36.4 nm, and its surface free energy was 135 mN / m². 2 .

[0057] From Example 1 and 3, it can be seen that using CaF2 as the B component can improve the leaching effect of lithium to some extent, and can also improve the fineness, distribution uniformity and surface free energy of the obtained iron phosphate.

[0058] Example 4

[0059] Compared with Example 1, the only difference is that in step (1), the calcination temperature is changed to 900℃, and the holding time for calcination is changed to 4h, and other operations and parameters are the same as Example 1.

[0060] The leaching rate of Li in the leaching solution is 99.4%. The D90 of the iron phosphate is 36.2nm, and the surface free energy is 136mN / m 2 .

[0061] Comparative Example 1

[0062] Compared with Example 1, the only difference is that in step (1), no joint treatment agent is added, and other operations and parameters are the same as Example 1.

[0063] The leaching rate of Li in the leaching solution is 45.2%, the D90 of the iron phosphate slag is 100.9nm, and the surface free energy is 105.3mN / m 2 .

[0064] Comparative Example 2

[0065] Compared with Example 1, the only difference is that in step (1), no B component is added in the joint treatment agent, and the missing B component is supplemented by the same weight of A component. Other operations and parameters are the same as Example 1.

[0066] The leaching rate of Li in the leaching solution is 78.3%. The D90 of the iron phosphate is 70.7nm, and the surface free energy is 122.6mN / m 2 .

[0067] Comparative Example 3

[0068] Compared with Example 1, the only difference is that in step (1), no A component is added in the joint treatment agent, and the missing A component is supplemented by the same weight of B component, and other operations and parameters are the same as Example 1.

[0069] The leaching rate of Li in the leaching solution is 51.3%. The D90 of the iron phosphate is 81.2nm, and the surface free energy is 112.3mN / m 2 .

[0070] Comparative Example 4

[0071] Comparative Example 3 except that the processing of Step (1) of Comparative Example 3 was conducted in an air atmosphere. The other operations and parameters were the same as in Example 1 (i.e., compared to Example 1, the difference was the absence of Component A and the change of the processing atmosphere to air).

[0072] The leaching rate of Li in the leachate was 89.6%. The D90 of the iron phosphate was between 58 nm and the surface free energy was 124.8 mN / m 2 .

[0073] Comparative Example 5

[0074] Comparative Example 3 except that the processing of Step (1) of Comparative Example 3 was conducted in an air atmosphere. The other operations and parameters were the same as in Example 1 (i.e., compared to Example 1, the difference was the absence of Component A and the change of the processing atmosphere to air).

[0075] The leaching rate of Li in the leachate was 58.9%. The D90 of the iron phosphate was 75.8 nm and the surface free energy was 116.9 mN / m 2 .

Claims

1. A method for recycling waste lithium iron phosphate cathode material, characterized in that, Waste lithium iron phosphate cathode material and combined treatment agent are mixed and calcined at a temperature above 600°C. The calcined material is then subjected to alkaline leaching treatment to separate lithium alkaline leaching solution and iron-phosphate slag. The combined treatment agent comprises component A and component B, wherein component A comprises at least one of FeO, Fe3O4, and Cu2O; and component B comprises at least one of CaF2, Al2O3, and SiO2.

2. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The lithium iron phosphate cathode material is an electrode material obtained by stripping the cathode from waste lithium iron phosphate batteries.

3. The method for recycling waste lithium iron phosphate cathode material as described in claim 2, characterized in that, In the lithium iron phosphate cathode material, the content of lithium iron phosphate active material is above 50 wt%.

4. The method for recycling waste lithium iron phosphate cathode material as described in claim 2, characterized in that, The lithium iron phosphate cathode material also contains at least one of a conductive agent and a binder.

5. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The A component is a composite of FeO and Cu2O.

6. The method for recycling waste lithium iron phosphate cathode material as described in claim 5, characterized in that, In component A, the weight ratio of FeO to Cu2O is 1:0.5~1.

5.

7. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The B component is CaF2.

8. The method for recycling waste lithium iron phosphate cathode materials as described in claims 1, 5, 6, or 7, characterized in that, The weight ratio of component A to component B is 1:0.1~1.

9. The method for recycling waste lithium iron phosphate cathode material as described in claim 8, characterized in that, The weight ratio of component A to component B is 1:0.2~0.

5.

10. The method for recycling waste lithium iron phosphate cathode material as described in claim 9, characterized in that, The weight ratio of component A to component B is 1:0.3~0.

4.

11. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The weight ratio of lithium iron phosphate in waste lithium iron phosphate cathode material to component A in the combined treatment agent is 1:1~5.

12. The method for recycling waste lithium iron phosphate cathode material as described in claim 11, characterized in that, The weight ratio of lithium iron phosphate in waste lithium iron phosphate cathode material to component A in the combined treatment agent is 1:3~4.

13. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The temperature during the calcination stage is 600~950℃.

14. The method for recycling waste lithium iron phosphate cathode material as described in claim 13, characterized in that, The temperature during the calcination stage is 800~900℃.

15. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The holding time at the calcination temperature is 2~6 hours.

16. The method for recycling waste lithium iron phosphate cathode material as described in claim 15, characterized in that, The holding time at the calcination temperature is 3-4 hours.

17. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The alkaline solution used in the alkaline leaching stage is a solution containing sodium hydroxide and potassium hydroxide; In the alkaline solution, the concentration of the solute is 0.5~1 M; The liquid-to-solid ratio during the alkaline leaching process is 20~40mL / g; The temperature during the alkali leaching stage is below 45℃; The alkali soaking stage should last for more than 30 minutes.

18. The method for recycling waste lithium iron phosphate cathode material as described in claim 17, characterized in that, The alkali soaking stage lasts for 1 to 2 hours.

19. The method for recycling waste lithium iron phosphate cathode material as described in claim 1, characterized in that, The alkali leaching residue obtained by alkali leaching is refined by melting and precipitation to obtain ferric phosphate.

20. The method for recycling waste lithium iron phosphate cathode material as described in claim 19, characterized in that, The temperature during the melting and refining stage is 350~500℃.

21. The method for recycling waste lithium iron phosphate cathode material as described in claim 20, characterized in that, The melting and refining process takes more than 1 hour.

22. The method for recycling waste lithium iron phosphate cathode material as described in claim 21, characterized in that, The melting and refining time is 1.5 to 4 hours.