Method for preparing lithium iron manganese phosphate positive electrode material by recycling waste lithium iron phosphate

Abstract

The invention discloses a method for preparing a lithium iron manganese phosphate positive electrode material by recycling waste lithium iron phosphate, which comprises the following steps: firstly, pretreating a waste lithium iron phosphate pole piece, and calcining in an inert atmosphere to obtain black waste lithium iron phosphate powder; mixing the waste lithium iron phosphate powder with a lithium source, a manganese source and a phosphorus source in a solution, and preparing an intermediate product through a hydrothermal / solvothermal method; and finally, mixing the intermediate product with a carbon source, carrying out ball milling, calcining the obtained material in an inert atmosphere, and naturally cooling after sintering to obtain the lithium manganese iron phosphate material. The method is simple to operate and low in cost, recycling of elements such as lithium, iron and phosphorus can be realized by recycling the waste lithium iron phosphate, and the cyclic utilization rate of resources can be increased.

Description

Technical Field

[0001] This invention relates to the field of battery material recycling and reuse technology, specifically a method for recycling waste lithium iron phosphate to prepare lithium manganese iron phosphate cathode material. Background Technology

[0002] With the rapid growth of global demand for renewable energy and electric vehicles, lithium-ion batteries, as a highly efficient and environmentally friendly energy storage device, have been widely used. Lithium iron phosphate (LiFePO4) cathode materials have become one of the mainstream choices in the power battery field due to their high safety, long cycle life, and low cost. However, with the increase in battery usage, a large number of retired lithium iron phosphate batteries are also generated, which not only wastes resources but may also pollute the environment. Therefore, how to efficiently recycle and reuse these retired battery materials has become an important issue in the current lithium-ion battery industry chain.

[0003] Currently, there are some existing technologies for the preparation of cathode materials from recycled waste lithium iron phosphate batteries. For example, Chinese patent document CN117977038A discloses a method for recycling waste lithium iron phosphate batteries to produce lithium manganese iron phosphate cathode materials. This method uses organic acid leaching and solid-state sintering to obtain the lithium manganese iron phosphate cathode material. Although existing technologies have made some progress in the recycling of waste lithium iron phosphate and the preparation of lithium manganese iron phosphate cathode materials, there are still many shortcomings. Existing processes generally suffer from high energy consumption and complex processes, which limit their large-scale industrial application. In addition, the recycling of retired batteries may lead to a decline in material performance. Therefore, a more efficient, environmentally friendly, and economical method for recycling waste lithium iron phosphate to prepare lithium manganese iron phosphate cathode materials is needed to achieve high-value utilization of waste lithium iron phosphate while meeting the performance requirements of lithium manganese iron phosphate cathode materials, thus solving the problems existing in the current technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate includes the following steps: S1: The waste lithium iron phosphate electrode sheets are pretreated and then calcined under an inert atmosphere to obtain waste lithium iron phosphate black powder. S2: Waste lithium iron phosphate powder is mixed with lithium source, manganese source and phosphorus source in solution, and intermediate product is prepared by hydrothermal / solvothermal method; S3: Mix the intermediate product with the carbon source, ball mill, and calcine the resulting material under an inert atmosphere. After sintering, allow it to cool naturally to obtain the recycled lithium manganese iron phosphate material.

[0006] As a further aspect of the present invention: the pretreatment method for the waste lithium iron phosphate electrode sheet in S1 is to soak the waste lithium iron phosphate electrode sheet in an organic solvent for 6-24 hours and then take it out and air dry it. The organic solvent used includes at least one of dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate.

[0007] As a further aspect of the present invention: the calcination conditions for the waste lithium iron phosphate electrode in S1 are a heating rate of 2~10 ℃·min-1, heating to 400~600 ℃, and holding at that temperature for 1~5 h.

[0008] As a further aspect of the present invention: the lithium source in S2 includes at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, and lithium oxalate, preferably lithium hydroxide; the manganese source includes at least one of manganese sulfate, manganese carbonate, manganese chloride, manganese acetate, manganese phosphate, and manganese hydroxide, preferably manganese sulfate; the phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate, preferably phosphoric acid.

[0009] As a further aspect of the present invention: the molar ratio of waste lithium iron phosphate and manganese source in S2 is (1~9):(9~1), and the molar ratio of manganese source, phosphorus source and lithium source is 1:1:x, where 1≤x≤3.

[0010] As a further aspect of the present invention: the solvent in S2 is a mixture of an organic solvent and water, wherein the organic solvent includes at least one of ethylene glycol, polyethylene glycol, isopropanol, n-butanol, and glycerol, preferably ethylene glycol.

[0011] As a further aspect of the present invention: the mixing reaction conditions in S2 are as follows: place the mixture in an oven, heat it to 100-200 ℃ at a rate of 2-5 ℃ / min, hold it at that temperature for 10-24 h, and then cool it with the oven.

[0012] As a further aspect of the present invention: the intermediate product in S2 is a two-phase mixture of lithium iron phosphate and lithium manganese iron phosphate.

[0013] As a further aspect of the present invention: the carbon source in S3 includes at least one of sucrose, glucose, maltose, starch, citric acid, phenolic resin, polyethylene glycol, polyethylene oxide, and polyvinylpyrrolidone.

[0014] As a further aspect of the present invention: the calcination conditions in S3 are a heating rate of 2~10 ℃·min-1, heating to 500~750 ℃, and holding for 1~10 h.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: By recycling waste lithium iron phosphate and converting it into high-value lithium manganese iron phosphate cathode material, this invention achieves the reuse of waste resources, reduces dependence on primary mineral resources, lowers production costs, and meets the requirements of a circular economy. Traditional methods of handling retired lithium batteries often pose environmental pollution risks, while this invention, through hydrothermal / solvothermal methods and heat treatment processes, avoids the emission of harmful substances, reduces negative environmental impacts, and has significant environmental benefits. The reaction conditions of this invention are mild, easy to implement industrially, and can effectively control the structure and performance of the products, improving production efficiency. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the present invention.

[0017] Figure 2 This is a scanning electron microscope image of waste lithium iron phosphate from Example 1.

[0018] Figure 3 This is a scanning electron microscope image of the intermediate product of Example 1.

[0019] Figure 4 This is a scanning electron microscope image of the regenerated lithium manganese iron phosphate from Example 1.

[0020] Figure 5 The X-ray diffraction patterns of waste lithium iron phosphate, intermediate products, and recycled lithium manganese iron phosphate in Example 1 are shown. Figure 6 The graph shows the rate performance of waste lithium iron phosphate and recycled lithium manganese iron phosphate in Example 1.

[0021] Figure 7 This is the Raman spectrum of regenerated lithium manganese iron phosphate in Example 1.

[0022] Figure 8 The X-ray photoelectron spectrum (Fe 2p) of the regenerated lithium manganese iron phosphate in Example 1 is shown.

[0023] Figure 9 The X-ray photoelectron spectrum (Mn 2p) of the regenerated lithium manganese iron phosphate in Example 1 is shown. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1, please refer to Figures 1-9 ; This invention provides a method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate, comprising the following steps: (1) 5g of waste lithium iron phosphate electrode sheet was added to 30mL of dimethyl carbonate solvent with a purity of 99% and soaked for 12h, and then the electrode sheet was dried. The dried waste lithium iron phosphate electrode sheet was heated to 500℃ at 5℃·min-1 under argon atmosphere and kept at the temperature for 3h to obtain waste lithium iron phosphate black powder.

[0026] (2) Weigh 0.03 mol of lithium hydroxide and add it to 30 mL of 98% pure ethylene glycol to form a lithium hydroxide solution.

[0027] (3) Add 0.01 mol manganese sulfate and 0.01 mol phosphoric acid to 5 mL of deionized water. After they are completely dissolved, add 25 mL of 98% ethylene glycol. Mix well and then add 0.01 mol of waste lithium iron phosphate powder to obtain mixed solution 1A.

[0028] (4) Add the lithium hydroxide solution from step (2) to the mixed solution 1A from step (3) and after mixing evenly, you will get mixed solution 1B.

[0029] (5) Transfer the mixed solution 1B from step (4) into the polytetrafluoroethylene liner of the reactor, tighten the hydrothermal reactor, place it in an oven, heat it to 180 ℃ at a rate of 2 ℃ / min at room temperature, keep it at that temperature for 10 h, and then cool it with the oven. Wash and dry to obtain the intermediate product.

[0030] (6) Take 1g of the intermediate product from step (5) and 0.2g of sucrose, add them to 5mL of anhydrous ethanol with a purity of 99.7%, ball mill at 450rpm for 2h, and then dry in an 80℃ drying oven overnight to obtain a mixture of phosphorus intermediate product and sucrose.

[0031] (7) The mixed material in step (6) is heated to 700 ℃ at 5 ℃·min-1 under an argon atmosphere and kept at the temperature for 4 h to obtain the recycled lithium manganese iron phosphate material. Example

[0032] This invention provides a method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate, comprising the following steps: (1) 5g of waste lithium iron phosphate electrode sheet was added to 50mL of dimethyl carbonate solvent with a purity of 99% and soaked for 24h, and then the electrode sheet was dried. The dried waste lithium iron phosphate electrode sheet was heated to 500℃ at 10℃·min-1 under argon atmosphere and kept at the temperature for 1h to obtain waste lithium iron phosphate black powder.

[0033] (2) Weigh 0.03 mol of lithium hydroxide and add it to 30 mL of 98% pure ethylene glycol to form a lithium hydroxide solution.

[0034] (3) Add 0.023 mol manganese carbonate and 0.023 mol phosphoric acid to 5 mL of deionized water. After they are completely dissolved, add 25 mL of 98% ethylene glycol. Mix well and then add 0.01 mol of waste lithium iron phosphate powder to obtain mixed solution 2A.

[0035] (4) Add the lithium hydroxide solution from step (2) to the mixed solution 2A from step (3) and wait until they are mixed evenly to obtain mixed solution 2B.

[0036] (5) Transfer the mixed solution 2B from step (4) into the polytetrafluoroethylene liner of the reactor, tighten the hydrothermal reactor, place it in an oven, heat it to 180 ℃ at a rate of 5 ℃ / min at room temperature, keep it at that temperature for 20 h, and then cool it with the oven. Wash and dry to obtain the intermediate product.

[0037] (6) Take 1g of the intermediate product from step (5) and 0.1g of sucrose, add them to 5mL of anhydrous ethanol with a purity of 99.7%, ball mill at 500rpm for 2h, and then dry them overnight in a forced-air drying oven at 80℃ to obtain a mixture of intermediate product and sucrose.

[0038] (7) The mixed material from step (6) is heated to 650 °C at 5 °C·min⁻¹ under an argon atmosphere and held for 4 h to obtain recycled lithium manganese iron phosphate material. Example 3 This invention provides a method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate, comprising the following steps: (1) 5g of waste lithium iron phosphate electrode sheet was added to 40mL of dimethyl carbonate solvent with a purity of 99% and soaked for 20h, and then the electrode sheet was dried. The dried waste lithium iron phosphate electrode sheet was heated to 500℃ at 5℃·min-1 under argon atmosphere and kept at the temperature for 1h to obtain waste lithium iron phosphate black powder.

[0039] (2) Weigh 0.06 mol of lithium hydroxide and add it to 60 mL of 98% pure ethylene glycol to form a lithium hydroxide solution.

[0040] (3) Add 0.03 mol manganese sulfate and 0.03 mol phosphoric acid to 10 mL of deionized water. After they are completely dissolved, add 50 mL of 98% ethylene glycol. Mix well and then add 0.02 mol of waste lithium iron phosphate powder to obtain mixed solution 3A.

[0041] (4) Add the lithium hydroxide solution from step (2) to the mixed solution 3A from step (3) and wait until they are mixed evenly to obtain mixed solution 3B.

[0042] (5) Transfer the mixed solution 3B from step (4) into the polytetrafluoroethylene liner of the reactor, tighten the hydrothermal reactor, place it in an oven, heat it to 180 ℃ at a rate of 2 ℃ / min at room temperature, keep it at that temperature for 10 h, and then cool it with the oven. Wash and dry to obtain the intermediate product.

[0043] (6) Take 2g of the intermediate product from step (5) and 0.4g of sucrose, add them to 10mL of anhydrous ethanol with a purity of 99.7% at a mass ratio of 5:1, ball mill at 450rpm for 2h, and then dry in an 80℃ drying oven overnight to obtain a mixture of intermediate product and sucrose.

[0044] (7) The mixed material from step (6) is heated to 600 ℃ at 5 ℃·min-1 under an argon atmosphere and kept at that temperature for 4 h to obtain the recycled lithium manganese iron phosphate material.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate, comprising the following steps: S1: The waste lithium iron phosphate electrode sheets are pretreated and then calcined under an inert atmosphere to obtain waste lithium iron phosphate black powder. S2: The intermediate product is prepared by mixing waste lithium iron phosphate black powder with lithium source, manganese source and phosphorus source in solution and then using hydrothermal / solvothermal method. S3: Mix the intermediate product with the carbon source, ball mill, and calcine the resulting material under an inert atmosphere. After sintering, allow it to cool naturally to obtain the recycled lithium manganese iron phosphate material.

2. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The pretreatment method for waste lithium iron phosphate electrodes in S1 is to soak the waste lithium iron phosphate electrodes in an organic solvent for 6-24 hours, and then take them out and air dry them. The organic solvent used includes at least one of dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate.

3. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The calcination conditions for the waste lithium iron phosphate electrode sheets in S1 are: a heating rate of 2~10 ℃·min-1, heating to 400~600℃, and holding at that temperature for 1~5 h.

4. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, S2 contains at least one of the following lithium sources: lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, and lithium oxalate; at least one of the following manganese sources: manganese sulfate, manganese carbonate, manganese chloride, manganese acetate, manganese phosphate, and manganese hydroxide; and at least one of the following phosphorus sources: phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

5. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The molar ratio of waste lithium iron phosphate black powder and manganese source in S2 is (1~9):(9~1), and the molar ratio of manganese source, phosphorus source and lithium source is 1:1:x, where 1≤x≤3.

6. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 2, characterized in that, The solvent in S2 is a mixture of an organic solvent and water, wherein the organic solvent includes at least one of ethylene glycol, polyethylene glycol, isopropanol, n-butanol, and glycerol.

7. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The mixing reaction conditions in S2 are as follows: place the mixture in an oven, heat it to 100-200°C at a rate of 2-5°C / min, hold it at that temperature for 10-24 hours, and then cool it with the oven.

8. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The intermediate product obtained in S2 is a two-phase mixture of lithium iron phosphate and lithium manganese iron phosphate.

9. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The carbon source in S3 includes at least one of sucrose, glucose, maltose, starch, citric acid, phenolic resin, polyethylene glycol, polyethylene oxide, and polyvinylpyrrolidone.

10. The method for preparing lithium manganese iron phosphate cathode material by recycling waste lithium iron phosphate according to claim 1, characterized in that, The calcination conditions in S3 are: a heating rate of 2~10 ℃·min-1, heating to 500~750 ℃, and holding at that temperature for 1~10 h.

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