A biomimetic method for pressurized repair of cathode materials from spent lithium iron phosphate batteries

Abstract

This invention discloses a pressurized biomimetic repair method for waste lithium iron phosphate battery cathode materials, comprising the following steps: S1, dispersing waste lithium iron phosphate cathode powder in deionized water, and adding a protective agent, soluble lithium salt, and biomimetic material to obtain a mixed solution; S2, transferring the mixed solution into a reaction vessel, and introducing gas while stirring; S3, heating the mixed solution in the reaction vessel to react, and allowing it to cool naturally to room temperature after the reaction; S4, filtering the solution after the reaction, and washing the product with a solvent; S5, drying the washed product to obtain relithiated lithium iron phosphate powder. This method solves the problems of slow defect repair and iron ion dissolution in existing lithium iron phosphate materials, achieving defect repair and regeneration of lithium iron phosphate materials while also improving cycle stability.

Description

Technical Field

[0001] This invention relates to the field of recycling waste lithium battery cathode materials, specifically to a pressurized biomimetic repair method for waste lithium iron phosphate battery cathode materials. Background Technology

[0002] Due to the relatively low economic efficiency of lithium iron phosphate cathode materials, direct recycling methods have seen rapid development in the field of spent lithium iron phosphate battery recycling in recent years. Currently, commonly used direct recycling methods include the hydrothermal method and the high-temperature solid-state method. The hydrothermal method has the advantages of being clean and requiring no quantitative lithium replenishment, and therefore has attracted considerable attention.

[0003] However, due to the relatively low temperature during hydrothermal treatment, the migration rate of lithium ions is slow, thus requiring prolonged hydrothermal treatment to repair lithium vacancy defects in spent lithium iron phosphate materials. Furthermore, lithium iron phosphate materials are easily oxidized during hydrothermal methods. Additionally, the Fe-O bonds in the lithium iron phosphate lattice are weak, and after long cycles, the dissolution of iron ions leads to irreversible capacity loss in the battery. Summary of the Invention

[0004] This invention provides a pressurized biomimetic repair method for cathode materials of spent lithium iron phosphate batteries, which solves the problems of slow repair of defects and iron ion dissolution in existing lithium iron phosphate materials. When applied, it can not only repair and regenerate lithium iron phosphate materials, but also improve cycle stability.

[0005] To solve this technical problem, the present invention provides the following technical solution:

[0006] A method for pressurized biomimetic repair of cathode materials from spent lithium iron phosphate batteries includes the following steps:

[0007] S1. Disperse waste lithium iron phosphate cathode powder in deionized water, and add protective agent, soluble lithium salt and biomimetic material to obtain a mixed solution;

[0008] S2. Transfer the mixed solution into the reaction vessel while stirring and introducing gas;

[0009] S3. Heat the mixed solution in the reactor to react, and allow it to cool naturally to room temperature after the reaction is complete;

[0010] S4. Filter the solution after the reaction and wash the product with solvent;

[0011] S5. Dry the washed product to obtain relithiated lithium iron phosphate powder.

[0012] This invention uses deionized water as a reaction solvent to add a certain amount of lithium source, protective agent, and biomimetic material to waste lithium iron phosphate. Gas is introduced, and a hydrothermal reaction is carried out under high pressure to obtain relithiated lithium iron phosphate material. High temperature can increase the ion exchange rate and thus shorten the reaction time. The addition of protective agent and high-pressure gas in the reaction vessel creates a reducing atmosphere to ensure that the material is not oxidized. High pressure also makes it easier for lithium ions to be added into the lattice of waste lithium iron phosphate. The added biomimetic material hemoglobin improves the d-band center of lithium iron phosphate, enhances the bonding between iron and oxygen, and inhibits iron dissolution during the cycle. This achieves the purpose of repairing and regenerating lithium iron phosphate material defects while improving cycle stability, thereby improving the performance of the recovered lithium iron phosphate cathode material.

[0013] Preferably, the carbon content of the waste lithium iron phosphate cathode powder in step S1 is between 5-10 wt%, and the total content of aluminum, copper, iron and other metal impurities is not higher than 1000 ppm.

[0014] Preferably, the soluble lithium salt in step S1 is selected from at least one of lithium oxalate, lithium hydroxide, lithium carbonate, lithium acetate, lithium phenolate, lithium phytate, lithium hydroquinone, or lithium glycolate, and its added mass is 5-15 wt% of the mass of the waste lithium iron phosphate cathode powder.

[0015] Preferably, the protective agent in step S1 is selected from at least one of citric acid, formic acid, oxalic acid, ascorbic acid, glucose, aniline, acetaldehyde, phenol, ferrous ammonium sulfate, or hydrogen peroxide, and its added mass is 5-20 wt% of the mass of the waste lithium iron phosphate cathode powder.

[0016] A protective agent was added to the reactor to create a reducing atmosphere and prevent the materials from being oxidized.

[0017] Preferably, the amount of deionized water added in step S1 is 50-80 mL of deionized water per gram of waste lithium iron phosphate.

[0018] Preferably, the biomimetic material in step S1 is selected from at least one of hemoglobin, hemospermia, or polyvinylpyrrolidone, and its added mass is 1-3 wt% of the mass of waste lithium iron phosphate cathode powder.

[0019] This invention improves the long-cycle performance of lithium iron phosphate by adding biomimetic materials such as hemoglobin during the hydrothermal process. These materials can enhance the d-band center of iron ions, thereby strengthening Fe-O bonding and inhibiting the dissolution of iron ions.

[0020] Preferably, the gas in step S2 is nitrogen, carbon dioxide, or argon, the pressure of the gas is 10-20 MPa, the stirring speed is between 100-400 r / min, and the stirring time is not less than 5 minutes.

[0021] In this invention, a high pressure of 10-20 MPa is applied to the reactor using gas to purge oxygen and protect the lithium iron phosphate material from oxidation. Simultaneously, the high pressure promotes the migration of lithium ions into the lithium iron phosphate lattice, increasing the hydrothermal relithiation rate.

[0022] Preferably, the reaction temperature in step S3 is 130-180℃ and the reaction time is 1-3 hours.

[0023] High temperatures can increase the ion exchange rate, thereby shortening the reaction time.

[0024] Preferably, the solvent in step S4 is water and ethanol, the washing is performed no less than 3 times, and at least one wash is performed with ethanol.

[0025] Preferably, the oven temperature in step S5 is between 80-110°C, and the drying time is not less than 8 hours.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention uses deionized water as a reaction solvent to add a certain amount of lithium source, protective agent and biomimetic material to waste lithium iron phosphate, introduces gas and carries out hydrothermal reaction under high pressure to obtain relithiated lithium iron phosphate material.

[0028] This invention uses deionized water as a clean solvent for the reaction. High temperature can increase the ion exchange rate and thus shorten the reaction time. Protective agents and high-pressure gas are added to the reaction vessel to create a reducing atmosphere to ensure that the material is not oxidized. High pressure also makes it easier for lithium ions to be added into the lattice of waste lithium iron phosphate. The added biomimetic material hemoglobin improves the d-band center of lithium iron phosphate, enhances the bonding between iron and oxygen, and inhibits iron dissolution during the cycle. This invention achieves the purpose of repairing and regenerating lithium iron phosphate material defects while improving cycle stability, thereby improving the performance of the recovered lithium iron phosphate cathode material.

[0029] Compared with the existing solid-phase method, the repair method used in this invention produces lithium iron phosphate with fewer defects, lower cost, and simpler process. The performance of lithium iron phosphate repaired by this method is also close to that of commercial lithium iron phosphate materials. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 This is a process flow diagram of the biomimetic repair method for pressurized cathode materials of waste lithium iron phosphate batteries according to the present invention.

[0032] Figure 2 The graphs show the cycling performance of the recycled lithium iron phosphate materials obtained in Examples 1-2 and the material obtained in Comparative Example 1 at 1C. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0034] Example 1

[0035] like Figure 1 As shown, Embodiment 1 of the present invention provides a method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries, which is implemented through the following steps:

[0036] Step 1

[0037] 1g of waste lithium iron phosphate cathode powder was dispersed in 50mL of aqueous solution and transferred to a reaction vessel. 8wt% lithium carbonate, 10% citric acid, and 1% hemoglobin were added. The carbon content of the waste lithium iron phosphate cathode powder ranged from 5-10wt%, and the total content of aluminum, copper, iron, and other metallic impurities did not exceed 1000ppm.

[0038] Step 2

[0039] The mixture was stirred at 200 r / min and nitrogen gas at 10 MPa was introduced into the reactor.

[0040] Step 3

[0041] Place the reactor in an oven and heat it at 150°C for 3 hours. After the reaction is complete, allow it to cool naturally to room temperature.

[0042] Step 4

[0043] The cooled reaction solution was filtered and washed with deionized water and ethanol, twice with water and once with ethanol.

[0044] Step 5

[0045] The material was dried in an oven at 80°C for 8 hours to obtain relithiated lithium iron phosphate powder.

[0046] Step 6

[0047] The relithiated lithium iron phosphate powder was assembled into a coin cell and charged and discharged. The discharge capacity at 1C rate was found to be stable at 145mAh / g.

[0048] Example 2

[0049] Embodiment 2 of the present invention provides a method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries, the method being implemented through the following steps:

[0050] Step 1

[0051] 1g of waste lithium iron phosphate cathode powder was dispersed in 50mL of aqueous solution and transferred to a reaction vessel. 8wt% lithium carbonate, 10% citric acid, and 10% hemoglobin were added. The carbon content of the waste lithium iron phosphate cathode powder ranged from 5-10wt%, and the total content of aluminum, copper, iron, and other metallic impurities did not exceed 1000ppm.

[0052] Step 2

[0053] The mixture was stirred at 200 r / min and nitrogen gas at 10 MPa was introduced into the reactor.

[0054] Step 3

[0055] Place the reactor in an oven and heat it at 150°C for 3 hours. After the reaction is complete, allow it to cool naturally to room temperature.

[0056] Step 4

[0057] The cooled reaction solution was filtered and washed with deionized water and ethanol, twice with water and once with ethanol.

[0058] Step 5

[0059] The material was dried in an oven at 80°C for 8 hours to obtain relithiated lithium iron phosphate powder.

[0060] Step 6

[0061] The relithiated lithium iron phosphate powder was assembled into a coin cell and charged and discharged. The discharge capacity at 1C rate was found to be stable at 137 mAh / g.

[0062] Example 3

[0063] Embodiment 3 of the present invention provides a method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries, the method being implemented through the following steps:

[0064] Step 1

[0065] 1g of waste lithium iron phosphate cathode powder was dispersed in 60mL of aqueous solution and transferred to a reaction vessel. 5wt% lithium carbonate, 20% citric acid, and 3% hemoglobin were added. The carbon content of the waste lithium iron phosphate cathode powder ranged from 5-10wt%, and the total content of aluminum, copper, iron, and other metallic impurities did not exceed 1000ppm.

[0066] Step 2

[0067] The mixture was stirred at 100 r / min and nitrogen gas at 10 MPa was introduced into the reactor.

[0068] Step 3

[0069] Place the reactor in an oven and heat it at 130°C for 3 hours. After the reaction is complete, allow it to cool naturally to room temperature.

[0070] Step 4

[0071] The cooled reaction solution was filtered and washed with deionized water and ethanol, twice with water and once with ethanol.

[0072] Step 5

[0073] The material was dried in a 90°C oven for 8 hours to obtain relithiated lithium iron phosphate powder.

[0074] Step 6

[0075] The relithiated lithium iron phosphate powder was assembled into a coin cell and charged and discharged. The discharge capacity at 1C rate was found to be stable at 145mAh / g.

[0076] Example 4

[0077] Embodiment 4 of the present invention provides a method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries, which is implemented through the following steps:

[0078] Step 1

[0079] 1g of waste lithium iron phosphate cathode powder was dispersed in 80mL of aqueous solution and transferred to a reaction vessel. 15wt% lithium carbonate, 5% citric acid, and 3% hemoglobin were added. The carbon content of the waste lithium iron phosphate cathode powder ranged from 5-10wt%, and the total content of aluminum, copper, iron, and other metallic impurities did not exceed 1000ppm.

[0080] Step 2

[0081] The mixture was stirred at 400 r / min and nitrogen gas at 20 MPa was introduced into the reactor.

[0082] Step 3

[0083] Place the reactor in an oven and heat it at 180°C for 1 hour. After the reaction is complete, allow it to cool naturally to room temperature.

[0084] Step 4

[0085] The cooled reaction solution was filtered and washed with deionized water and ethanol, twice with water and once with ethanol.

[0086] Step 5

[0087] The material was dried in an oven at 110°C for 8 hours to obtain relithiated lithium iron phosphate powder.

[0088] Step 6

[0089] The relithiated lithium iron phosphate powder was assembled into a coin cell and charged and discharged. The discharge capacity at 1C rate was found to be stable at 145mAh / g.

[0090] Comparative Example 1

[0091] Comparative Example 1 of this invention provides a method for repairing cathode materials from spent lithium iron phosphate batteries, the method being implemented through the following steps:

[0092] Step 1

[0093] 1g of waste lithium iron phosphate cathode powder was dispersed in 50mL of aqueous solution and transferred to a reaction vessel. 8wt% lithium carbonate and 10% citric acid were added.

[0094] Step 2

[0095] The mixture was stirred at 200 r / min and nitrogen gas at 10 MPa was introduced into the reactor.

[0096] Step 3

[0097] Place the reactor in an oven and heat it at 150°C for 3 hours. After the reaction is complete, allow it to cool naturally to room temperature.

[0098] Step 4

[0099] The cooled reaction solution was filtered and washed with deionized water and ethanol, twice with water and once with ethanol.

[0100] Step 5

[0101] The material was dried in an oven at 80°C for 8 hours to obtain relithiated lithium iron phosphate powder.

[0102] Step 6

[0103] The relithiated lithium iron phosphate powder was assembled into a coin cell and charged and discharged. The discharge capacity at 1C rate was found to be stable at 90mAh / g.

[0104] like Figure 2As shown in Examples 1-2 above, waste lithium iron phosphate was reacted with deionized water as the solvent, and a certain amount of lithium source, protective agent, and biomimetic material were added. Gas was introduced, and a hydrothermal reaction was carried out under high pressure to obtain relithiated lithium iron phosphate material. High temperature can increase the ion exchange rate and thus shorten the reaction time. The addition of protective agent and high-pressure gas in the reactor creates a reducing atmosphere to ensure that the material is not oxidized. High pressure also makes it easier for lithium ions to be added into the lattice of waste lithium iron phosphate. The pressure in the reactor and hemoglobin have a significant impact on the specific capacity and cycle stability of relithiated lithium iron phosphate. The amount of hemoglobin added should not be too much or too little. When the amount added is 1% of the lithium iron phosphate material, relatively better performance is obtained. After repair, the discharge specific capacity at 1C rate increases from 85mAh / g to 145mAh / g. When the amount added is 10% of the lithium iron phosphate material, the material performance decreases slightly. The added biomimetic material hemoglobin enhances the d-band center of lithium iron phosphate, strengthens the bonding between iron and oxygen, and inhibits iron dissolution during cycling. This achieves the goal of repairing and regenerating lithium iron phosphate materials while also improving cycle stability, thereby improving the performance of the recovered lithium iron phosphate cathode material.

[0105] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries, characterized in that, Includes the following steps: S1. Disperse waste lithium iron phosphate cathode powder in deionized water, and add protective agent, soluble lithium salt and biomimetic material to obtain a mixed solution; S2. Transfer the mixed solution into the reaction vessel, and while stirring, introduce gas, which is nitrogen, at a pressure of 10-20 MPa. S3. Heat the mixed solution in the reactor to react, and allow it to cool naturally to room temperature after the reaction is complete; S4. Filter the solution after the reaction and wash the product with solvent; S5. Dry the washed product to obtain relithiated lithium iron phosphate powder. The protective agent mentioned in step S1 is selected from citric acid, and its added mass is 5-20 wt% of the mass of waste lithium iron phosphate cathode powder; The biomimetic material mentioned in step S1 is selected from hemoglobin or hemospermia, and its added mass is 1-3 wt% of the mass of waste lithium iron phosphate cathode powder.

2. The method for pressurized biomimetic repair of waste lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The carbon content of the waste lithium iron phosphate cathode powder mentioned in step S1 is between 5-10 wt%, and the total content of aluminum, copper, iron and other metal impurities is not higher than 1000 ppm.

3. The method for pressurized biomimetic repair of waste lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The soluble lithium salt mentioned in step S1 is selected from at least one of lithium oxalate, lithium hydroxide, lithium carbonate, lithium acetate, lithium phenolate, lithium phytate, lithium hydroquinone, or lithium glycolate, and its added mass is 5-15 wt% of the mass of the waste lithium iron phosphate cathode powder.

4. The method for pressurized biomimetic repair of waste lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The amount of deionized water added in step S1 is 50-80 mL of deionized water per gram of waste lithium iron phosphate.

5. The method for pressurized biomimetic repair of waste lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step S2, the stirring speed is between 100-400 r / min, and the stirring time is not less than 5 minutes.

6. The method for pressurized biomimetic repair of waste lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The reaction temperature in step S3 is 130-180℃, and the reaction time is 1-3 hours.

7. The method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries according to claim 1, characterized in that, The solvents used in step S4 are water and ethanol, and the washing is performed no less than three times, with at least one wash using ethanol.

8. The method for pressurized biomimetic repair of cathode materials from waste lithium iron phosphate batteries according to claim 1, characterized in that, The drying temperature in step S5 is between 80-110℃, and the drying time is not less than 8 hours.

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