A process for directly regenerating spent lithium iron phosphate cathode material and its application

Abstract

The present invention discloses a process for directly regenerating spent lithium iron phosphate cathode materials and its application. The direct regeneration process includes a preliminary treatment step of soaking, stirring, filtering, washing, and drying the spent lithium iron phosphate cathode materials, a secondary treatment step of calcining the preliminary treated materials, and a tertiary treatment step of stirring, filtering, and drying the secondary treated materials with a lithium salt mixed solution. Finally, the tertiary treatment step also includes the steps of mixing the tertiary treated materials with a carbon source, ball milling, and calcining, thereby obtaining the directly regenerated lithium iron phosphate cathode materials. The direct regeneration process for spent lithium iron phosphate cathode materials of the present invention is simple and has low pollution. At the same time, the regenerated cathode materials have excellent performance when used in batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of waste power lithium battery recycling, and in particular to a process for directly regenerating failed lithium iron phosphate positive electrode materials and its application. Background Art

[0002] Since the introduction of new energy vehicles in my country in 2013, the average lifespan of power batteries has been 5-8 years, and the first batch of power batteries released into the market are essentially nearing retirement. Currently, the first batch of new energy vehicle power batteries is expected to be recycled in 2023, with the first wave of recycling expected to arrive in the next few years. Recycling power batteries in a green, low-carbon, and efficient manner not only increases the economic benefits of recycled resources but also reduces environmental pollution, which is of great significance to the development of new energy in my country.

[0003] Currently, the primary recycling process for spent lithium iron phosphate batteries is a wet process: after dissolving the cathode plate with a strong acid, an alkali is added to separate the lithium, iron, and phosphate ions in the solution by precipitating them. This lengthy and complex process, coupled with the extensive use of chemicals that contribute to greenhouse gas emissions and wastewater pollution, has hindered widespread adoption. Therefore, there is an urgent need to develop a process for the direct regeneration of spent lithium iron phosphate cathode materials that is low-cost, low-pollution, and allows the regenerated product to be used directly as cathode material. Summary of the Invention

[0004] In response to the defects in the existing technology, the present invention proposes a process for directly regenerating failed lithium iron phosphate positive electrode materials and its application. The present invention can better recycle failed materials through direct regeneration, breaking through the limitations of traditional recycling processes.

[0005] In one aspect, the present invention provides a process for directly regenerating spent lithium iron phosphate cathode material, comprising the following steps:

[0006] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred, followed by filtration, and the filtrate was washed with an organic solvent and dried to obtain a preliminary treatment of the spent lithium iron phosphate cathode material;

[0007] S2. The failed lithium iron phosphate cathode material after the preliminary treatment is calcined to obtain a secondary treatment of the failed lithium iron phosphate cathode material, at which point the remaining PVDF and other impurities can be removed;

[0008] S3. The failed lithium iron phosphate cathode material powder of the secondary treatment was added to a mixed solution of deionized water and an alcohol solvent containing a lithium salt, stirred, filtered and then dried to obtain a three-time treatment of the failed lithium iron phosphate cathode material;

[0009] S4. The spent lithium iron phosphate cathode material processed three times is mixed with a carbon source material and ball-milled, and then calcined to obtain a directly regenerated lithium iron phosphate cathode material.

[0010] The process of directly regenerating spent lithium iron phosphate cathode materials of the present invention can directly recycle retired lithium iron phosphate batteries on the market. The process is short and easy to operate, which can greatly reduce pollution and save production costs. In addition, the regenerated lithium iron phosphate cathode materials have excellent performance.

[0011] Furthermore, the lithium salt in step S3 is one or more of lithium acetylacetonate, lithium acetylacetate, and lithium iodide, preferably any one of lithium acetylacetonate and lithium acetylacetate. The lithium salt is dissolved in a water-alcohol mixed solution, and then lithium iron phosphate black powder is added to react with the black powder to produce a chelate reaction, thereby adjusting the near-surface structure, thereby effectively removing the degraded amorphous phase and residual fluorine compounds. Through direct lithium connection and reduced diffusion barriers, the reconstructed surface promotes the relithiation process, which is conducive to the rapid completion of lithium replenishment and repair processes at high temperatures.

[0012] Furthermore, the amount of carbon source material added in step S4 is 5%-16% of the mass of the failed lithium iron phosphate positive electrode material, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and preferably 10%-13%, such as 10%, 11%, 12%, 13%.

[0013] Furthermore, the organic solvent in step S1 is one or more of ethanol, methanol, N-methylpyrrolidone, NN-dimethylformamide, and dimethyl sulfoxide.

[0014] Furthermore, in step S2, the calcination temperature is 250-450°C, such as 250°C, 300°C, 350°C, 400°C, 450°C, and the calcination time is 0.5-2h, such as 0.5h, 1h, 1.5h, 2h.

[0015] Furthermore, in step S4, the ball milling time is 0.5-5h, such as 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, and the ball milling speed is 50-220r / min, such as 50, 80, 100, 120, 150, 180, 200, 220r / min.

[0016] Furthermore, the carbon source in step S4 is one or more of cellulose, sucrose, tannic acid, glucose, and vitamin C. The inventors have found that the cycle performance of lithium iron phosphate positive electrode materials can be significantly improved by reacting a mixed solution of lithium salt and water alcohol with lithium iron phosphate black powder and adding a carbon source for ball milling.

[0017] Furthermore, in step S4, the calcination temperature is 500-700°C, such as 500°C, 550°C, 600°C, 650°C, and 700°C, and the calcination time is 2-6h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, and 6h.

[0018] Furthermore, the concentration of the mixed solution containing lithium salt in step S3 is 3-10 wt %.

[0019] Furthermore, the calcination in step S4 is performed under a specific atmosphere, such as any one of nitrogen, argon or argon-hydrogen mixed gas.

[0020] Furthermore, the drying in step S1 can be performed in a vacuum drying oven at a drying temperature of 50-80°C.

[0021] Furthermore, the drying in step S3 can be performed in a vacuum drying oven at a drying temperature of 40-80° C. and a drying time of 5-8 hours.

[0022] Furthermore, in the mixed solution of deionized water and alcohol solvent in step S3, the volume ratio of the two is 1:(1-2). Adding lithium salt to the water-alcohol mixed solution can significantly improve the reaction efficiency with lithium iron phosphate black powder.

[0023] Furthermore, the stirring time in step S1 is 2-7 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, and 6 hours.

[0024] Furthermore, the stirring time in step S3 is 5-12 hours, and the stirring is performed at normal temperature and pressure.

[0025] Furthermore, the amount of the spent lithium iron phosphate positive electrode material powder added in the secondary treatment in step S3 is 0.001-10 g.

[0026] Furthermore, the alcohol solvent is selected from any one or more of ethanol, methanol or propanol.

[0027] Another aspect of the present invention provides the application of the direct regeneration process in treating waste power lithium-ion batteries.

[0028] Finally, the present invention also provides a lithium iron phosphate positive electrode material regenerated by the direct regeneration process.

[0029] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0030] (1) The performance of the lithium iron phosphate cathode material product regenerated by the direct regeneration process provided by the present invention is comparable to that of commercial lithium iron phosphate cathode materials;

[0031] (2) The direct regeneration process provided by the present invention is simple and suitable for large-scale industrial applications;

[0032] (3) The direct regeneration process provided by the present invention does not involve reagents that may cause environmental pollution, and the regeneration process does not produce wastewater or waste residue, which is environmentally friendly and the entire process is green and efficient;

[0033] (4) The direct regeneration process provided by the present invention can perform coupled impurity removal at room temperature and pressure, reconstruct the lithium replenishment channel, and then efficiently and directly regenerate the failed lithium iron phosphate at high temperature for a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a 1C charge-discharge curve of the regenerated lithium iron phosphate positive electrode material obtained in Example 1;

[0036] Figure 2 This is a 1C long cycle curve of the regenerated lithium iron phosphate cathode material obtained in Example 1;

[0037] Figure 3 This is a 1C charge-discharge curve of the regenerated lithium iron phosphate positive electrode material obtained in Example 2;

[0038] Figure 4 This is a 1C long cycle curve of the regenerated lithium iron phosphate cathode material obtained in Example 2;

[0039] Figure 5 This is a 1C charge-discharge curve of the regenerated lithium iron phosphate positive electrode material obtained in Example 3;

[0040] Figure 6 This is a 1C long cycle curve of the regenerated lithium iron phosphate cathode material obtained in Example 3;

[0041] Figure 7 1C charge-discharge curve of the lithium iron phosphate positive electrode material after final treatment obtained in Comparative Example 1;

[0042] Figure 8 This is a 1C long cycle curve of the lithium iron phosphate positive electrode material after final treatment obtained in Comparative Example 1. DETAILED DESCRIPTION

[0043] In order to help those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0044] Example

[0045] The present invention is further described below with reference to specific examples and comparative examples. The following specific examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and are particularly not limited to the types of the various component raw materials used in the following specific examples.

[0046] 1. The sources of raw materials for the embodiments and comparative examples are as follows:

[0047] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present invention are all commercially available. The spent lithium iron phosphate cathode material was purchased from a battery disassembly manufacturer (Hebei Zhonghua Lithium Battery Technology Co., Ltd.).

[0048] 2. Various performance test methods

[0049] The regenerated lithium iron phosphate positive electrode material was mixed with positive electrode slurry in the mass ratio of regenerated lithium iron phosphate positive electrode material: conductive agent SP: binder PVDF: NMP = 80:10:10:100, coated on aluminum foil, and vacuum dried at 100°C for 12 hours before cutting to obtain electrode sheets. Subsequently, CR2032 button batteries were assembled in a glove box according to the button battery assembly process.

[0050] (1) Gram capacity performance test: tested by Xinwei battery testing system, the charging cut-off voltage is 4.3V, and the minimum discharge cut-off voltage is 2.5V.

[0051] (2) Long cycle stability test: The test is performed using the Xinwei battery test system with a rate set to 1C.

[0052] Example 1

[0053] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0054] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0055] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60°C for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0056] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 7% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0057] The battery charge and discharge curve of the regenerated lithium iron phosphate cathode material obtained in Example 1 is as follows Figure 1 As shown, by comparing with the button battery assembled with normal commercial lithium iron phosphate positive electrode material, it can be seen that the charge and discharge curves of the regenerated lithium iron phosphate positive electrode material in this embodiment are consistent with those of the normal commercial lithium iron phosphate positive electrode material, and the capacity and cycle performance are excellent, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate positive electrode material regenerated by this method has good electrochemical properties, with a discharge capacity of 138mAh / g at 1C and a capacity retention rate of 72.8% after 400 charge and discharge cycles, showing excellent rate performance, as shown in FIG. Figure 1 、 Figure 2 shown.

[0058] Example 2

[0059] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0060] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0061] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60°C for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0062] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 10% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0063] The battery charge and discharge curve of the regenerated lithium iron phosphate cathode material obtained in Example 2 is as follows Figure 3 As shown in the figure, by comparing with the button cell assembled with normal commercial lithium iron phosphate positive electrode material, it can be seen that the charge and discharge curves of the regenerated lithium iron phosphate positive electrode material in this embodiment are consistent with those of the normal commercial lithium iron phosphate positive electrode material, and the capacity and cycle performance are excellent, meeting the national standards for lithium iron phosphate batteries. The lithium iron phosphate material recycled by this method has good electrochemical properties, with a discharge capacity of 144mAh / g at 1C and a capacity retention rate of 92.4% after 400 charge and discharge cycles, showing excellent rate performance. Figure 3 、 Figure 4 shown.

[0064] Example 3

[0065] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0066] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0067] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60°C for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0068] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 15% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0069] The battery charge and discharge curve of the regenerated lithium iron phosphate cathode material obtained in Example 3 is as follows Figure 5As shown, by comparing with the button battery assembled with normal commercial lithium iron phosphate positive electrode material, it can be seen that the regenerated lithium iron phosphate positive electrode material of this embodiment has the same charge and discharge curve as the normal commercial lithium iron phosphate positive electrode material, and has excellent capacity and cycle performance, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has good electrochemical properties, with a discharge capacity of 133mAh / g at 1C and a capacity retention rate of 85% after 400 charge and discharge cycles, showing excellent rate performance. Figure 5 、 Figure 6 shown.

[0070] Example 4

[0071] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 hours, followed by filtration. The filtrate was washed with N-methylpyrrolidone and dried in a vacuum drying oven at 50°C to obtain a preliminarily treated spent lithium iron phosphate cathode material.

[0072] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 250 ° C for 2 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0073] S3. 16 mg (10% wt. in a water-alcohol mixed solution) of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 12 h, filtered, and dried in a vacuum drying oven at 80°C for 5 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0074] S4. The spent lithium iron phosphate cathode material treated three times was mixed with cellulose (the added amount was 5% wt of the spent lithium iron phosphate cathode material) and ball-milled for 5 hours at a ball-milling speed of 220 rpm, and then calcined at 700°C for 3 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate cathode material.

[0075] The regenerated lithium iron phosphate positive electrode material of this embodiment has excellent capacity and cycle performance, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has good electrochemical properties, with a discharge capacity of 135mAh / g at 1C and a capacity retention rate of 70% after 400 charge and discharge cycles, showing excellent rate performance.

[0076] Example 5

[0077] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 3 hours, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 70°C to obtain a preliminarily treated spent lithium iron phosphate cathode material.

[0078] S2. The initially treated spent lithium iron phosphate cathode material was calcined at 450°C for 1 h to obtain a secondary treated spent lithium iron phosphate cathode material;

[0079] S3. 4.8 mg (3% wt. in a water-alcohol mixed solution) of lithium acetoacetate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:2), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 5 h, filtered, and dried in a vacuum drying oven at 40°C for 8 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0080] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 16% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 0.5 h at a ball-milling speed of 60 rpm, and then calcined at 500 ° C for 6 h in a nitrogen atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0081] The regenerated lithium iron phosphate positive electrode material of this embodiment has excellent capacity and cycle performance, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has good electrochemical properties, with a discharge capacity of 140mAh / g at 1C and a capacity retention rate of 82% after 400 charge and discharge cycles, showing excellent rate performance.

[0082] Example 6

[0083] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0084] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0085] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium acetoacetate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60° C. for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0086] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 10% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0087] The regenerated lithium iron phosphate positive electrode material of this embodiment has excellent capacity and cycle performance, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has good electrochemical properties, with a discharge capacity of 141 mAh / g at 1C and a capacity retention rate of 90% after 400 charge and discharge cycles, showing excellent rate performance.

[0088] Example 7

[0089] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0090] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0091] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium iodide was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60° C. for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0092] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 10% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0093] The regenerated lithium iron phosphate positive electrode material of this embodiment has excellent capacity and cycle performance, which meets the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has good electrochemical properties, with a discharge capacity of 137 mAh / g at 1C and a capacity retention rate of 88% after 400 charge and discharge cycles, showing excellent rate performance.

[0094] Comparative Example 1

[0095] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0096] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0097] S3. 0 mg of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol in a volume ratio of 1:1 (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60°C for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material;

[0098] S4. The spent lithium iron phosphate cathode material treated three times was mixed with 0% glucose and ball-milled for 2 h at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 h in an argon atmosphere to obtain the final treated lithium iron phosphate cathode material.

[0099] The difference between Comparative Example 1 and Example 1 is that no lithium salt is added in step S3, and no carbon source material is added for ball milling in step S4. The capacity and cycle performance of the lithium iron phosphate positive electrode material obtained in this comparative example are significantly lower than those in Example 1, and do not meet the national standards for lithium iron phosphate batteries. Figure 7 、 Figure 8 As shown, the lithium iron phosphate material finally obtained after treatment by this method has poor electrochemical performance, with a discharge capacity of 124 mAh / g at 1C, and the charge and discharge cycle cannot be maintained after 250 cycles.

[0100] Comparative Example 2

[0101] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0102] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0103] S3. 8 mg (5% wt) of lithium acetylacetonate was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60°C for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material;

[0104] S4. The spent lithium iron phosphate cathode material treated three times was ball-milled for 2 h at a ball-milling speed of 160 rpm, and then calcined at 600 °C for 6 h in an argon atmosphere to obtain a directly regenerated lithium iron phosphate cathode material.

[0105] The difference between Comparative Example 2 and Example 1 is that no carbon source material is added for ball milling in step S4. The capacity and cycle performance of the regenerated lithium iron phosphate positive electrode material in this comparative example are significantly reduced compared with Example 1, and do not meet the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has poor electrochemical performance, with a discharge capacity of 128 mAh / g at 1C and a capacity retention rate of 45% after 400 charge and discharge cycles.

[0106] Comparative Example 3

[0107] S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred for 6 h, followed by filtration. The filtrate was washed with ethanol and dried in a vacuum drying oven at 80 ° C to obtain a preliminarily treated spent lithium iron phosphate cathode material;

[0108] S2. The failed lithium iron phosphate cathode material after the preliminary treatment was calcined at a temperature of 350 ° C for 0.5 h to obtain a secondary treatment of the failed lithium iron phosphate cathode material;

[0109] S3. 8 mg (5% wt. in a water-alcohol mixed solution) of lithium hydroxide was dissolved in a mixed solution of deionized water and ethanol (volume ratio 1:1), and then 160 mg of the secondary treated spent lithium iron phosphate cathode material powder was added to the mixed solution. The mixture was magnetically stirred at room temperature for 10 h, filtered, and dried in a vacuum drying oven at 60° C. for 6 h to obtain the tertiary treated spent lithium iron phosphate cathode material.

[0110] S4. The spent lithium iron phosphate positive electrode material treated three times was mixed with glucose (the added amount was 7% wt of the spent lithium iron phosphate positive electrode material) and ball-milled for 2 hours at a ball-milling speed of 160 rpm, and then calcined at 600 ° C for 6 hours in an argon atmosphere to obtain a directly regenerated lithium iron phosphate positive electrode material.

[0111] The difference between Comparative Example 3 and Example 1 is that the lithium salt used in step S3 is lithium hydroxide. Since lithium hydroxide cannot undergo a coupling reaction with the surface of the black powder, the capacity and cycle performance of the regenerated lithium iron phosphate positive electrode material in this comparative example are significantly reduced compared with Example 1, and do not meet the national standards for lithium iron phosphate batteries. The lithium iron phosphate material regenerated by this method has poor electrochemical performance, with a discharge capacity of 126 mAh / g at 1C and a capacity retention rate of 50% after 400 charge and discharge cycles.

[0112] The direct regeneration process of the failed lithium iron phosphate positive electrode material of Examples 1-7 of the present invention is to achieve coupled impurity removal at room temperature and pressure, reconstruct the lithium replenishment channel, and then efficiently and directly regenerate and repair the failed lithium iron phosphate at high temperature for a short time through multi-step special treatment of the failed positive electrode material, and at the same time add a specific lithium salt to react with the organic solvent in step S3, and then efficiently and directly regenerate and repair the failed lithium iron phosphate at high temperature for a short time, and the regenerated lithium iron phosphate positive electrode material can reach a level comparable to the product performance of normal commercial lithium iron phosphate positive electrode material, with excellent capacitance and cycle performance, in line with the national standards of lithium iron phosphate batteries, and showing excellent rate performance, and because the regeneration process is simple and has little pollution, it can be suitable for large-scale industrial applications. Therefore, the direct regeneration process of the failed lithium iron phosphate positive electrode material of the present invention has obvious advantages over the comparative example and can effectively meet the high standards of customers and the market.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for directly regenerating spent lithium iron phosphate cathode material, characterized in that: The steps include: S1. The spent lithium iron phosphate cathode material was immersed in deionized water and stirred, followed by filtration, and the filtrate was washed with an organic solvent and dried to obtain a preliminary treatment of the spent lithium iron phosphate cathode material; S2. The failed lithium iron phosphate cathode material is calcined to obtain a secondary treatment of the failed lithium iron phosphate cathode material; S3. The failed lithium iron phosphate cathode material powder of the secondary treatment was added to a mixed solution of deionized water and an alcohol solvent containing a lithium salt, stirred, filtered and then dried to obtain a three-time treatment of the failed lithium iron phosphate cathode material; S4. The three-time treatment of the failed lithium iron phosphate cathode material and the carbon source material was mixed and milled and calcined to obtain a directly regenerated lithium iron phosphate cathode material; The lithium salt in step S3 is one or more of lithium acetylacetonate and lithium acetylacetate.

2. The direct regeneration process according to claim 1, characterized in that The amount of the carbon source material added in step S4 is 5-16% of the mass of the spent lithium iron phosphate positive electrode material.

3. The direct regeneration process according to claim 1, characterized in that In step S2, the calcination temperature is 250-450° C., and the calcination time is 0.5-2 h.

4. The direct regeneration process according to claim 1, characterized in that In step S4, the ball milling time is 0.5-5 hours, and the ball milling speed is 50-220 r / min.

5. The direct regeneration process according to claim 1, characterized in that In step S4, the carbon source material is one or more of cellulose, sucrose, tannic acid, glucose, and vitamin C.

6. The direct regeneration process according to claim 1, characterized in that In step S4, the calcination temperature is 500-700° C., and the calcination time is 2-6 hours.

7. The direct regeneration process according to claim 1, characterized in that The concentration of the mixed solution containing lithium salt in step S3 is 3-10 wt %.

8. Use of the direct regeneration process according to any one of claims 1 to 7 in the treatment of waste power lithium-ion batteries.

9. Lithium iron phosphate positive electrode material regenerated by the direct regeneration process according to any one of claims 1 to 7.

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