Regenerated lithium iron phosphate material, preparation method and application thereof

Abstract

The application belongs to the field of waste battery material recycling, and particularly relates to a regenerated lithium iron phosphate material and a preparation method and application thereof, wherein the preparation method of the regenerated lithium iron phosphate material is as follows: waste lithium iron phosphate material is subjected to liquid phase treatment in an aqueous solution of a treating agent A, and then a first treated material is obtained by separation; the treating agent A is at least one of ammonia, sodium hydroxide, potassium hydroxide, EDTA, EDTA sodium salt and EDTA potassium salt; the first treated material and a treating agent B are subjected to calcination modification treatment at a temperature of 300-600 DEG C to obtain a modified material; the treating agent B comprises FeCl2; the modified material is mixed with phosphoric acid for leaching treatment to obtain ferrous phosphate slag and lithium liquid; the ferrous phosphate slag is subjected to lithiumization calcination to prepare the regenerated lithium iron phosphate material. The method can realize green recycling of waste LFP with low three wastes, and can directly regenerate the regenerated lithium iron phosphate with high performance, especially excellent fast charging performance.

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] Lithium iron phosphate batteries have the characteristics of green safety, low cost, excellent electrochemical performance, etc., and play an important role in the field of battery positive electrode materials, and their market share is increasing year by year. However, the service life of waste lithium iron phosphate batteries is usually 5-8 years, and a large number of retired power lithium iron phosphate batteries need to be recycled. If recycling is not considered, the key resources required for lithium-ion batteries will soon be exhausted, and in addition, it will pose a serious threat to human safety.

[0003] For waste lithium iron phosphate, the existing main treatment means is solid-phase roasting and wet leaching process.

[0004] For example, the patent document with publication number CN115084698A discloses a waste lithium iron phosphate material regeneration method: the first recovery material is obtained by pretreating the waste lithium iron phosphate material-containing recovery object, wherein the first recovery material includes waste lithium iron phosphate material; the second recovery material is obtained by adding a regeneration solution to the first recovery material for reaction, wherein the regeneration solution includes a reducing organic acid, a lithium salt, and an inorganic acid; the pH value of the regeneration solution is 7.0±0.5; the second recovery material is subjected to post-treatment to obtain regenerated lithium iron phosphate material. Again, the patent document with publication number CN117265254A discloses a method for recovering lithium by acid roasting of waste lithium iron phosphate positive electrode material, which specifically records that the waste lithium iron phosphate positive electrode material and a sulfuric acid salt are mixed and roasted at a temperature of 450-750°C to obtain a roasted product; the roasted product is leached in a liquid at a temperature of 20-50°C to obtain a lithium-rich solution.

[0005] However, the current recycling method usually requires a large amount of acid, alkali reagent, and consumption of oxidizing agent, reducing agent, etc. The recycled positive electrode material is suitable for low-rate charging and discharging requirements, and the fast-charging performance is poor, which restricts the application prospect of the regenerated material. SUMMARY

[0006] In view of the problems existing in the recycling of waste lithium iron phosphate battery positive electrode, the present application aims to provide a preparation method of regenerated lithium iron phosphate material, which aims to greenly regenerate regenerated lithium iron phosphate material with high electrochemical performance such as excellent fast-charging performance.

[0007] The second object of the present application is to provide regenerated lithium iron phosphate prepared by the preparation method and its application in lithium-ion batteries.

[0008] A preparation method of a regenerated lithium iron phosphate material, wherein waste lithium iron phosphate material is subjected to liquid phase treatment in an aqueous solution of a treating agent A, and then a first treated material is obtained by separation; the treating agent A is at least one of ammonia, sodium hydroxide, potassium hydroxide, EDTA, sodium EDTA salt, and potassium EDTA salt;

[0009] The first treated material and a treating agent B are subjected to calcination modification treatment at a temperature of 300-600 DEG C to obtain a modified material; wherein the treating agent B comprises FeCl2.

[0010] The modified material is mixed with phosphoric acid for leaching treatment to obtain ferrous phosphate residue and lithium liquor.

[0011] The ferrous phosphate residue is subjected to lithiumization calcination to obtain the regenerated lithium iron phosphate material.

[0012] The waste lithium iron phosphate battery positive material is treated by the treating agent A in the liquid phase, and then the treating agent B is used for solid phase modification treatment, so that the phase change calcination effect can be strengthened based on the special Lewis acid effect of the treating agent B, and high-quality ferrous phosphate residue can be formed by subsequent phosphoric acid leaching, and the waste LFP can be recycled in a low-three-waste manner, and in addition, high-performance regenerated lithium iron phosphate with excellent fast-charging performance can be directly regenerated.

[0013] The waste lithium iron phosphate material is obtained by disassembling and peeling from the waste battery. The peeling method can be known in the industry. For example, the waste lithium iron phosphate battery is discharged, disassembled, and peeled (e.g., peeled by an organic solvent NMP) to obtain waste positive electrode powder. In the present application, considering the simplicity of the process, the waste lithium iron phosphate battery positive material can also contain at least one of a conductive agent, a binder, and an electrolyte.

[0014] In the present application, the content of lithium iron phosphate in the waste lithium iron phosphate material is not particularly required, and considering the economy of the process, the content of the active material is preferably above 50 wt.%, further preferably above 80 wt.%, and more preferably 80-95 wt.%.

[0015] In the present application, the concentration of the treating agent A in the aqueous solution of the treating agent A can be reasonably adjusted as required, for example, it can be 0.01-0.5 M.

[0016] In the present application, the liquid-solid ratio in the liquid phase treatment process is 10-30 mL / g.

[0017] In the present application, the temperature of the liquid phase treatment process is 25-60 DEG C, and the treatment time is 0.5-3 h.

[0018] In one preferred scheme of the application, the liquid-phase treatment process comprises a first-stage liquid-phase treatment process with the pretreatment agent A1, a second-stage liquid-phase treatment process with the treatment agent A2, and a third-stage liquid-phase treatment process with the treatment agent A3.

[0019] The treatment agent A1 is ammonia water; the treatment agent A2 is at least one of sodium hydroxide and potassium hydroxide; and the treatment agent A3 is at least one of EDTA, EDTA sodium salt, and EDTA potassium salt.

[0020] In the application, the combined treatment of the special treatment agents A1 to A3 can achieve synergy and further optimize the physicochemical structure of the waste lithium iron phosphate material, so as to help further improve the electrochemical performance of the regenerated lithium iron phosphate material in combination with the modification process of the subsequent treatment agent B.

[0021] Further, the concentration of the treatment agent A1 can be 0.2 to 0.3 M; the concentration of the treatment agent A2 can be 0.05 to 0.1 M; and the concentration of the treatment agent A3 can be 0.03 to 0.05 M.

[0022] The time of each stage of treatment can be reasonably adjusted as needed, for example, can be 30 to 60 min.

[0023] In the application, the solid-phase modification treatment with the treatment agent B of FeCl2 can strengthen the roasting effect, and is beneficial to the direct obtaining of ferrous phosphate slag by phosphoric acid leaching, so that the regenerated lithium iron phosphate material can be directly regenerated without changing the valence.

[0024] In the application, the FeCl2 can be a component without crystalline water or a component with crystalline water.

[0025] In the application, the weight ratio of the treatment material of the first stage to the treatment agent B is 1:1 to 4; and preferably 1:2 to 3.

[0026] In the application, the temperature of the roasting modification treatment can be 450 to 550 DEG C.

[0027] In the application, the time of the roasting modification can be 0.5 to 5 h, and further can be 1 to 2 h.

[0028] In the application, the roasting modification process is carried out under the assistance of microwave. In the application, the roasting modification with the treatment agent B is combined with the microwave modification means, which is helpful to further synergistically strengthen the electrochemical performance of the prepared regenerated lithium iron phosphate.

[0029] In the present application, the power of the microwave is not particularly required, for example, it can be 200-1000 MHz, and further can be 400-600 MHz.

[0030] In the present application, when the preferred microwave heating mode is selected, the processing time can be shortened to 20-40 min. In the present application, the optimized use of the microwave can improve the processing efficiency, and can also be combined with the physicochemical properties of the processing agent B to synergistically optimize the physicochemical structure of the positive electrode and the selective optimization of beneficial elements, so as to unexpectedly facilitate the fast charging performance of the regenerated material.

[0031] In the present application, the concentration of phosphoric acid in the leaching process is 0.01-0.2 M; further can be 0.03-0.1 M. In the present application, the low-concentration phosphoric acid can be used to realize the green regeneration of waste LFP positive electrode.

[0032] The liquid-solid ratio in the leaching process is 20-50 mL / g, and the first step can be 30-45 mL / g;

[0033] The leaching time can be reasonably adjusted as required, for example, it can be 10-20 min;

[0034] In the present application, iron powder is also added in the leaching process. The amount of iron powder can be 5-10 wt.% of the modified material. In the present application, the use of iron powder in the leaching process helps to further optimize the material phase and trace hybrid characteristics, and helps to strengthen the fast charging performance of the regenerated LFP to a certain extent.

[0035] The pH of the lithium liquid is adjusted to 5-6 by ammonia water in advance, and then the lithium is treated by carbonation and precipitation to obtain a lithium product;

[0036] The lithium product is used as a lithium source for lithiation roasting treatment.

[0037] In the present application, a carbon source is also selectively added in the lithiation roasting; for example, it can be monosaccharide, disaccharide, polysaccharide, polymer, pitch, etc. The amount of the carbon source can be reasonably adjusted as required, for example, it can be 4-15 wt.% of the weight of the precursor.

[0038] The lithiation roasting process includes a first holding process and a second holding process, wherein the temperature of the first holding process is 300-400 DEG C; the temperature of the second holding process is 650-750 DEG C; further, the temperature of the first holding process is 340-360 DEG C; the temperature of the second holding process is 700-750 DEG C;

[0039] The first holding time is 0.5-2 h; the second holding time is 8-15 h; further, the first holding time is 1-1.5 h; the second holding time is 10-12 h.

[0040] The application also provides the regenerated lithium iron phosphate material prepared by the preparation method.

[0041] The application also provides application of the regenerated lithium iron phosphate material prepared by the preparation method, which is used as an active material to prepare a lithium ion battery.

[0042] Advantages

[0043] The application innovatively performs liquid-phase treatment on the waste lithium iron phosphate battery positive electrode material by using a treatment agent A, and then performs solid-phase modification treatment by using a treatment agent B, so that the phase change roasting effect can be strengthened based on the special Lewis acid effect of the treatment agent B, and high-quality ferrous phosphate slag can be formed by subsequent phosphoric acid leaching, and the regenerated lithium iron phosphate with high performance, especially excellent fast-charging performance, can be directly regenerated by lithiumizing roasting.

[0044] The application research also shows that the liquid-phase modification treatment is performed by using the treatment agent A1 to the treatment agent A3 in combination, and / or the solid-phase modification treatment is performed by using the treatment agent B with microwave assistance, so that the fast-charging performance of the regenerated material can be further synergized and optimized. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The XRD pattern of the regenerated LFP of Example 1 and the waste LFP;

[0046] Figure 2 The XRD pattern of the leaching slag of step 4 of Example 1;

[0047] Figure 3 The SEM pattern of the leaching slag of step 4 of Example 1;

[0048] Figure 4 The SEM pattern of the regenerated LFP prepared in Example 1;

[0049] Figure 5 The first circle specific capacity voltage pattern of the regenerated LFP prepared in Example 1; DETAILED DESCRIPTION

[0050] The application will be further described in detail below in combination with specific embodiments, but the application is not limited to the following embodiments.

[0051] In the application, the active material content in the waste lithium iron phosphate battery positive electrode material is not particularly required, and the content is preferably above 50 wt.%, considering the economy of the process, and in the following cases, the active content is 85-90 wt.% unless otherwise stated.

[0052] Example 1

[0053] Step 1: Liquid-phase pretreatment:

[0054] The waste lithium iron phosphate battery positive electrode material (XRD see Figure 1 ) is treated by liquid phase, and the steps are as follows:

[0055] First, the first section of material is obtained by ultrasonic treatment at 50±5°C for 40 min using treatment agent A1 (0.3M dilute ammonia water, liquid-solid ratio 20mL / g), and then the second section of material is obtained by ultrasonic treatment at 50±5°C for 40 min using treatment agent A2 (0.08M NaOH solution, liquid-solid ratio 20mL / g), and then the third section of material is obtained by ultrasonic treatment at 50±5°C for 40 min using treatment agent A3 (0.03M EDTA solution, liquid-solid ratio 10mL / g), and then solid-liquid separation is performed to obtain the third section of material;

[0056] Step 2: phase change roasting:

[0057] The product after the final treatment in step 1 (the third section of material in this case) is mixed with treatment agent B (FeCl2·4H2O) at a weight ratio of 1:3, and then heat treated at 500°C for 1h under Ar atmosphere to obtain modified material;

[0058] Step 3: leaching:

[0059] The modified material in step 2 is mixed with iron powder, wherein the addition amount of Fe powder is 5-10wt.% of the modified material. At room temperature, 0.05M H3PO4 is first added at a liquid-solid ratio of 40:1 mL / g for leaching for 20 min, and then the H3PO4 concentration in the system is adjusted to 0.1 M by adding phosphoric acid, and leaching is performed for 30 min. The leaching rate of metal Li is Li99.9%.

[0060] Step 4: separation and precipitation:

[0061] For the above solution, the filtrate and the solid are obtained by filtration, the solid is treated by magnetic separation to obtain the filter residue, and the filter residue is ferrous phosphate (Fe3(PO4)2·8H2O, XRD see Figure 2 , SEM see Figure 3 ).

[0062] For the filtrate, NH3·H2O is first added to adjust the pH to 5-6 for impurity removal treatment, and Fe(OH)3 is precipitated from the solution, and then the filtrate obtained after filtration is added with saturated sodium carbonate to obtain Li2CO3 by evaporation crystallization.

[0063] Step 5: regeneration: argon atmosphere, two-stage roasting:

[0064] First paragraph: The filter residue (ferrous phosphate salt) obtained in step 4 and Li2CO3 were first calcined at 300°C for 1 h at a Li:Fe:P molar ratio of 1.05:1:1;

[0065] Second paragraph: 5wt.% of glucose was added to the precursor (total weight of filter residue and lithium carbonate) for carbon-coated calcination, and the operation conditions were 700°C for 12 h, to obtain the regenerated lithium iron phosphate positive electrode active material (regenerated LFP, XRD is shown in Figure 1 , SEM is shown in Figure 4 ).

[0066] Test:

[0067] The coin cell was assembled in a glove box:

[0068] The positive electrode tested: The regenerated LFP active material: acetylene black: PVDF were weighed according to the mass ratio of 9:0.5:0.5, and then coated on the positive electrode current collector (Al) after slurry to form the positive electrode to be tested.

[0069] The electrolyte: 1.5M LiPF6 was used as the electrolyte (FEC:DEC:EMC=1:1:1), and 0.5wt.% of LiDFOB was added to the electrolyte.

[0070] The separator was Celgard2400 polypropylene film.

[0071] Lithium was used as the counter electrode.

[0072] The CR2025 battery was assembled and tested, and the regenerated positive electrode at 1C rate at room temperature showed a reversible capacity of 140mAh / g (the first cycle specific capacity voltage diagram is shown in Figure 5 ).

[0073] Example 2

[0074] Compared with Example 1, the only difference is that the conditions of step 1 are changed, and the experimental groups are as follows:

[0075] Group A: The liquid phase pretreatment process only includes the treatment agent A1 treatment process, and the time is extended to 120 min;

[0076] Group B: The liquid phase pretreatment process only includes the treatment agent A2 treatment process, and the time is extended to 120 min;

[0077] Group C: The liquid phase pretreatment process only includes the treatment agent A3 treatment process, and the time is extended to 120 min;

[0078] Group D: In the liquid phase pretreatment process, only the treatment agent A1 and the treatment agent A2 processes are carried out, and the treatment time of each is 60 min;

[0079] Group E: first treatment with treatment agent A2, then treatment with treatment agent A1, and finally treatment with treatment agent A3;

[0080] Group F: the concentration of treatment agent A1 is 0.2 M, the liquid-solid ratio is 10 mL / g, and the treatment time is 30 min; the concentration of treatment agent A2 is 0.06 M, the liquid-solid ratio is 10 mL / g, and the treatment time is 50 min; the concentration of treatment agent A3 is 0.04 M, the liquid-solid ratio is 30 mL / g, and the treatment time is 20 min;

[0081] Other operations and parameters are the same as in Example 1.

[0082] Example 3

[0083] Compared with Example 1, the only difference is that the conditions of step 2 are changed, and the experimental groups are as follows:

[0084] Group A: the product after final treatment in step 1 is mixed with treatment agent B (FeCl2·4H2O) at a weight ratio of 1:2, and then heat-treated at 550°C for 1.5 h under Ar atmosphere to obtain a modified material;

[0085] Group B: the heat treatment is assisted by microwaves, wherein the power of the microwaves is 500 MHz, and the treatment time is 30 min.

[0086] Other operations and parameters are the same as in Example 1.

[0087] Example 4

[0088] Compared with Example 1, the only difference is that the conditions of step 3 are changed, and the experimental groups are as follows:

[0089] Group A: no iron powder is added, and the amount of treatment agent B is the same as in Example 1;

[0090] Group B: during the leaching process, 0.03 M H3PO4 is first added at a liquid-solid ratio of 30:1 mL / g at room temperature and leached for 30 min, and then the concentration of H3PO4 in the system is adjusted to 0.08 M by adding phosphoric acid, and leached for 40 min.

[0091] Other operations and parameters are the same as in Example 1.

[0092] Example 5

[0093] Compared with Example 1, the only difference is that in step 5, in the first section, the low-temperature calcination temperature is 350°C, and the time is 1.5 h; in the second section, starch is used instead of glucose, and the amount is 10% of the mass of the precursor; in addition, the calcination temperature is 750°C, and the time is 10 h. Other operations and parameters are the same as in Example 1.

[0094] Comparative Example 1

[0095] Compared with Example 1, the only difference is that no treatment agent A1, treatment agent A2 and treatment agent A3 are added in the modification process of step 1, and other operations and parameters are the same as those in Example 1.

[0096] Comparative Example 2

[0097] Compared with Example 1, the only difference is that FeCl3·6H2O is used to replace treatment agent B in step 2, and other operations and parameters are the same as those in Example 1.

[0098] Comparative Example 3

[0099] Compared with Example 1, the only difference is that zinc chloride is used to replace treatment agent B in step 2, and other conditions are the same as those in Example 1.

[0100] The results of each example and comparative example are shown in Table 1.

[0101]

[0102] As can be seen from the examples and comparative examples, the positive electrode material of the waste lithium iron phosphate battery is treated by liquid treatment of treatment agent A and then solid-phase modification treatment of treatment agent B, so that the phase change roasting effect can be strengthened based on the special Lewis acid effect of treatment agent B, which is beneficial to the subsequent phosphoric acid leaching to form high-quality ferrous phosphate slag, and the lithiumization roasting can directly regenerate high-performance regenerated lithium iron phosphate, especially with excellent fast-charging performance.

[0103] As can be seen from Example 1 and Example 2, through the combined treatment of the special treatment agent A1~treatment agent A3, the physicochemical structure of the waste lithium iron phosphate material can be further optimized, which is helpful to further improve the electrochemical performance of the regenerated lithium iron phosphate material.

[0104] As can be seen from Example 1 and Example 3, the roasting modification with treatment agent B and the microwave modification method can further synergistically improve the electrochemical performance of the prepared regenerated lithium iron phosphate.

[0105] As can be seen from Example 1 and Example 4, the low-concentration phosphoric acid leaching with iron assistance can further synergistically improve the electrochemical performance of the prepared regenerated lithium iron phosphate.

Claims

1. A method for preparing recycled lithium iron phosphate material, characterized in that, Waste lithium iron phosphate material is subjected to liquid phase treatment, and then separated to obtain a processed material; the liquid phase treatment process includes a first liquid phase treatment process pretreated with treatment agent A1, a second liquid phase treatment process treated with treatment agent A2, and a third liquid phase treatment process treated with treatment agent A3; Treatment agent A1 is ammonia water; treatment agent A2 is at least one of sodium hydroxide and potassium hydroxide; treatment agent A3 is at least one of EDTA, sodium EDTA salt, and potassium EDTA salt. A section of the treated material and a treatment agent B are calcined and modified at a temperature of 300~600℃ to obtain a modified material; wherein, the treatment agent B is FeCl2; The modified material and phosphoric acid were mixed and leached to obtain ferrous phosphate slag and lithium liquid; The recycled lithium iron phosphate material is obtained by lithium-ion roasting of ferrous phosphate slag.

2. The method for preparing recycled lithium iron phosphate material as described in claim 1, characterized in that, Waste lithium iron phosphate material is material obtained from the stripping of waste lithium iron phosphate batteries; the content of lithium iron phosphate is above 50 wt.%.

3. The method for preparing recycled lithium iron phosphate material as described in claim 1, characterized in that, The weight ratio of the first-stage treatment material to the treatment agent B is 1:1~4.

4. The method for preparing recycled lithium iron phosphate material as described in claim 1, characterized in that, The calcination modification process was carried out with microwave assistance.

5. The method for preparing recycled lithium iron phosphate material as described in claim 1, characterized in that, During the leaching process, the concentration of phosphoric acid is 0.01~0.2M; The liquid-to-solid ratio during the leaching process is 20~50 mL / g; The leaching time is 10-20 minutes.

6. The method for preparing recycled lithium iron phosphate material as described in claim 5, characterized in that, Iron powder is also added during the leaching process; the amount of iron powder added is 5~10 wt. of the modified material.

7. The method for preparing recycled lithium iron phosphate material as described in claim 1, characterized in that, A carbon source is also added during lithiation roasting; The lithiation roasting process includes a first-stage heat preservation process and a second-stage heat preservation process. The temperature of the first-stage heat preservation process is 300~400℃, and the temperature of the second-stage heat preservation process is 650~750℃. The first insulation period is 0.5 to 2 hours; the second insulation period is 8 to 15 hours.

8. A regenerated lithium iron phosphate material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of a recycled lithium iron phosphate material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, It is used as an active material in the preparation of lithium-ion batteries.

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