Method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive electrode material

Abstract

The application discloses a method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive electrode materials, and belongs to the technical field of waste battery material recycling. The method comprises the following steps: (1) obtaining a positive electrode sheet from a waste lithium iron phosphate battery; (2) heat-treating the positive electrode sheet to obtain lithium iron phosphate; (3) taking the lithium iron phosphate, adding the lithium iron phosphate into inorganic acid to react, filtering, and obtaining a filtrate; (4) adding a manganese source and a phosphorus source into the filtrate, stirring, then adjusting the pH to alkaline, separating, and drying to obtain a solid; (5) grinding the solid, a fullerene trifluoromethyl derivative and polyvinyl alcohol, and baking under a protective gas atmosphere to obtain an intermediate; and (6) grinding the intermediate, mixing the intermediate with graphene and glucose, and calcining under a mixed gas atmosphere composed of hydrogen and a protective gas to prepare lithium manganese iron phosphate. The lithium manganese iron phosphate prepared by the method has high specific capacity and good cycle stability when used as a positive electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste battery material recycling, and particularly relates to a method for recycling waste lithium iron phosphate battery positive electrode material to prepare lithium manganese iron phosphate. BACKGROUND

[0002] With the popularity and faster and faster updating of electronic products, such as computer, tablet and mobile phone products, the use amount of rechargeable lithium batteries is also increasing.

[0003] Lithium iron phosphate batteries have the characteristics of high specific energy, high voltage platform, long cycle life, high safety and good rate performance, resulting in that lithium iron phosphate batteries are widely used. This also leads to the generation of a large number of waste lithium iron phosphate batteries. If not fully recycled, it will not only waste resources, but also cause environmental pollution.

[0004] Compared with lithium iron phosphate, lithium manganese iron phosphate has the advantages of high working potential, large energy density and long cycle life. However, the specific capacity and cycle performance of the existing lithium manganese iron phosphate battery still need to be further improved.

[0005] Therefore, it is urgent to provide a method for recycling lithium iron phosphate batteries and preparing lithium manganese iron phosphate. This not only greatly reduces the preparation cost of lithium manganese iron phosphate, but also is conducive to the full use of resources. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a method for recycling waste lithium iron phosphate battery positive electrode material to prepare lithium manganese iron phosphate. The method fully utilizes the lithium iron phosphate battery positive electrode material, greatly reduces the preparation cost of lithium manganese iron phosphate, and has the effect of turning waste into treasure. In addition, the lithium manganese iron phosphate prepared by the present application has high specific capacity and good cycle stability when used as a positive electrode material.

[0007] In order to achieve the above purpose, the present application realizes the following technical scheme.

[0008] A method for recycling waste lithium iron phosphate battery positive electrode material to prepare lithium manganese iron phosphate, comprising the following steps:

[0009] (1) obtaining a positive electrode sheet from a waste lithium iron phosphate battery;

[0010] (2) heat treating the positive electrode sheet obtained in step (1) to obtain lithium iron phosphate and aluminum foil;

[0011] (3) taking the lithium iron phosphate obtained in step (2) and adding it to an inorganic acid to react, and filtering to obtain a filtrate;

[0012] (4) taking the filtrate obtained in step (3), adding a manganese source and a phosphorus source into the filtrate, stirring, then adjusting the pH to be alkaline, separating, drying to obtain a solid;

[0013] (5) grinding and mixing the solid obtained in step (4), a fullerene trifluoromethyl derivative and polyvinyl alcohol, performing roasting under a protective gas atmosphere, then cooling to obtain an intermediate;

[0014] (6) grinding the intermediate obtained in step (5), then mixing with graphene and glucose, then performing calcination under a mixed gas atmosphere of hydrogen and a protective gas, cooling to prepare the lithium manganese iron phosphate.

[0015] Preferably, in step (1), the specific process of obtaining the positive electrode sheet is as follows: discharging, disassembling the waste lithium iron phosphate battery to obtain a positive electrode sheet, a negative electrode sheet and a separator, washing the positive electrode sheet, drying and reserving.

[0016] Preferably, in step (2), the temperature of the heat treatment is 480-580℃, and the time of the heat treatment is 1.5-2.5 hours, further preferably, the temperature of the heat treatment is 500-550℃, and the time of the heat treatment is 2-2.5 hours.

[0017] Preferably, in step (2), the aluminum foil is recycled as an aluminum resource. For example, higher-purity aluminum is obtained by smelting.

[0018] Preferably, in step (3), the inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid or nitric acid.

[0019] Preferably, in step (3), the temperature of the reaction is 75-100℃, and the time of the reaction is 1-6 hours.

[0020] Preferably, in step (3), the ratio of the lithium iron phosphate to the inorganic acid is 100g:(300-600)mL, further preferably 100g:(380-450)mL.

[0021] Preferably, the concentration of the inorganic acid is 1-5mol / L, further preferably 2-4mol / L.

[0022] Preferably, in step (4), the manganese source is selected from at least one of manganese sulfate, manganese carbonate or manganese nitrate.

[0023] Preferably, in step (4), the phosphorus source is selected from at least one of monobasic ammonium phosphate or ammonium phosphate.

[0024] Preferably, in step (4), the mass ratio of the lithium iron phosphate to the manganese source is 100:(50-80), further preferably 100:(55-70).

[0025] Preferably, in step (4), the mass ratio of the lithium iron phosphate to the phosphorus source is 100:(30-70), further preferably 100:(40-60).

[0026] Preferably, in step (4), the pH is adjusted to 8-12.

[0027] Preferably, in step (4), the pH is adjusted to alkaline by using ammonia or sodium hydroxide.

[0028] Preferably, in step (4), the temperature of the stirring is 45-65℃, and the time of the stirring is 5-10 hours.

[0029] Preferably, in step (4), the separation process includes filtration and washing.

[0030] Preferably, in step (5), the mass ratio of the solid, the fullerene trifluoromethyl derivative and the polyvinyl alcohol is 100:(1-5):(1-12), further preferably 100:(2-4):(3-10).

[0031] Preferably, in step (5), the fullerene trifluoromethyl derivative is C 60 (CF3) 24 The selection of the fullerene trifluoromethyl derivative is conducive to obtaining a stable coating layer structure on the surface of the lithium manganese iron phosphate, and also optimizes the charge transfer path, which is conducive to improving the cycle stability of the lithium manganese iron phosphate.

[0032] Preferably, in step (5), the protective gas atmosphere includes nitrogen or a noble gas, such as argon or helium.

[0033] Preferably, in step (5), the calcination process is: heating at a rate of 5-10℃ / min to 200-250℃, holding for 1-2 hours, then heating at a rate of 1-4℃ / min to 320-350℃, holding for 2-4 hours. With this calcination process, the fullerene trifluoromethyl derivative and the solid can fully react chemically, which promotes the improvement of the specific capacity of the finally prepared lithium manganese iron phosphate, and is also conducive to maintaining the good cycle stability of the lithium manganese iron phosphate.

[0034] Preferably, in step (6), the mass ratio of the intermediate to graphene and glucose is 100:(0.5-4):(1-10), further preferably 100:(0.5-3):(2-10).

[0035] Preferably, in step (6), the calcination process is as follows: heating at a rate of 3-10℃ / min to 300-450℃, holding for 1-2 hours, then heating at a rate of 1-5℃ / min to 650-700℃, holding for 3-5 hours. Under this calcination process, the carbonization of glucose occurs at the same time, and it is easier to form a multi-level carbon coating layer with graphene, which not only inhibits and stabilizes the volume expansion of lithium manganese iron phosphate during the charging and discharging cycle, but also optimizes the charge transfer path, enhances the surface electronic conductivity of the material, and reduces the interface polarization.

[0036] The method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive electrode material has the application in the field of batteries.

[0037] Compared with the prior art, the method has the following beneficial effects:

[0038] The method not only makes full use of the lithium iron phosphate battery positive electrode material, but also uses fullerene trifluoromethyl derivatives, polyvinyl alcohol, and graphene, and glucose to perform staged roasting and calcination treatment, so that the lithium manganese iron phosphate can make full use of the electronic properties of fullerene trifluoromethyl derivatives and graphene, and obtain a stable coating layer structure on the surface of the lithium manganese iron phosphate, which not only inhibits and stabilizes the volume expansion of lithium manganese iron phosphate during the charging and discharging cycle, but also optimizes the charge transfer path, enhances the surface electronic conductivity of the material, and reduces the interface polarization. BRIEF DESCRIPTION OF DRAWINGS

[0039] The application will be further described below with reference to the accompanying drawings.

[0040] Figure 1 The discharge cycle curve of the button cell assembled by the lithium manganese iron phosphate prepared in Example 3 of the application. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the application will be described below in a clear and complete manner with reference to the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the application. Meanwhile, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial channels or can be obtained by known methods, if not otherwise specified.

[0042] Example 1

[0043] A method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive electrode material, comprising the following steps:

[0044] (1) Discharge the waste lithium iron phosphate battery, disassemble, get the positive plate, negative plate and diaphragm, wash the positive plate, dry, standby;

[0045] (2) The positive plate obtained in step (1) is heat treated, the heat treatment temperature is 500 DEG C, the heat treatment time is 2 hours, lithium iron phosphate and aluminum foil are obtained, and the aluminum foil is recycled as aluminum resources;

[0046] (3) The lithium iron phosphate obtained in step (2) is added into hydrochloric acid (the concentration of hydrochloric acid is 2 mol / L), the reaction temperature is 80 DEG C, the reaction time is 3.5 hours, the dosage ratio of lithium iron phosphate to hydrochloric acid is 100 g:400 mL, and the filtrate is obtained by filtration;

[0047] (4) Take the filtrate obtained in step (2), add manganese carbonate and ammonium phosphate to the filtrate, the mass ratio of lithium iron phosphate to manganese carbonate is 100:70, the mass ratio of lithium iron phosphate to ammonium phosphate is 100:50, stir at 55 DEG C for 30 minutes, then adjust the pH to 11 with ammonia water, continue to stir at 55 DEG C for 6 hours, filter, wash and dry to obtain a solid;

[0048] (5) The solid obtained in step (4), fullerene trifluoromethyl derivative (C 60 (CF3) 24 ) and polyvinyl alcohol are mixed by grinding, the mass ratio of solid, fullerene trifluoromethyl derivative and polyvinyl alcohol is 100:1.5:4, and the calcination is carried out under argon atmosphere, the calcination process is as follows: heating to 220 DEG C at a rate of 8 DEG C / min, holding for 2 hours, then heating to 330 DEG C at a rate of 2 DEG C / min, holding for 2 hours, and then cooling to obtain an intermediate;

[0049] (6) The intermediate obtained in step (5) is ground and mixed with graphene and glucose, the mass ratio of intermediate, graphene and glucose is 100:1:4, and then calcination is carried out under a mixed gas atmosphere of hydrogen and argon (the volume ratio of hydrogen to argon is 1:1), the calcination is carried out at a rate of 5 DEG C / min to 700 DEG C for 6 hours, and then cooled to prepare lithium manganese iron phosphate.

[0050] Example 2

[0051] A method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive material, comprising the following steps:

[0052] (1) Discharge the waste lithium iron phosphate battery, disassemble, get the positive plate, negative plate and diaphragm, wash the positive plate, dry, standby;

[0053] (2) The positive electrode sheet obtained in step (1) is subjected to heat treatment, the temperature of the heat treatment is 480℃, the time of the heat treatment is 2.5 hours, lithium iron phosphate and aluminum foil are obtained, and the aluminum foil is recycled as aluminum resources;

[0054] (3) The lithium iron phosphate obtained in step (2) is added into hydrochloric acid (the concentration of the hydrochloric acid is 3mol / L), the reaction temperature is 85℃, the reaction time is 3 hours, the dosage ratio of the lithium iron phosphate to the hydrochloric acid is 100g:420mL, and filtration is performed to obtain a filtrate;

[0055] (4) The filtrate obtained in step (2) is taken, manganese sulfate and monobasic ammonium phosphate are added into the filtrate, the mass ratio of the lithium iron phosphate to the manganese sulfate is 100:75, the mass ratio of the lithium iron phosphate to the monobasic ammonium phosphate is 100:60, stirring is performed at 55℃ for 30 minutes, then the pH is adjusted to 10 by using ammonia water, and stirring is continuously performed at 55℃ for 6 hours, filtration, washing and drying are performed to obtain a solid;

[0056] (5) The solid obtained in step (4), fullerene trifluoromethyl derivative (C 60 (CF3) 24 ) and polyvinyl alcohol are ground and mixed, the mass ratio of the solid, the fullerene trifluoromethyl derivative and the polyvinyl alcohol is 100:1:5, roasting is performed under an argon atmosphere, the roasting process is as follows: the temperature is increased to 220℃ at a rate of 5℃ / min, and then the temperature is kept for 2 hours, then the temperature is increased to 330℃ at a rate of 4℃ / min, and then the temperature is kept for 3 hours, and then cooling is performed to obtain an intermediate;

[0057] (6) The intermediate obtained in step (5) is ground and mixed with graphene and glucose, the mass ratio of the intermediate, the graphene and the glucose is 100:1.5:4.5, and then calcination is performed under a mixed gas atmosphere composed of hydrogen and argon (the volume ratio of the hydrogen to the argon is 1:1), the calcination is performed by increasing the temperature to 700℃ at a rate of 5℃ / min for 6 hours, and then cooling is performed to prepare lithium manganese iron phosphate.

[0058] Example 3

[0059] A method for recycling and preparing lithium manganese iron phosphate from waste lithium iron phosphate battery positive electrode material, comprising the following steps:

[0060] (1) The waste lithium iron phosphate battery is discharged, disassembled to obtain a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet is washed and dried for standby use;

[0061] (2) The positive electrode sheet obtained in step (1) is subjected to heat treatment, the temperature of the heat treatment is 500℃, the time of the heat treatment is 2 hours, lithium iron phosphate and aluminum foil are obtained, and the aluminum foil is recycled as aluminum resources;

[0062] (3) The lithium iron phosphate obtained in step (2) is added into hydrochloric acid (the concentration of the hydrochloric acid is 2 mol / L) and reacted at 80°C for 3.5 hours, the amount ratio of the lithium iron phosphate to the hydrochloric acid is 100 g:400 mL, and then filtered to obtain a filtrate;

[0063] (4) The filtrate obtained in step (2) is taken, manganese carbonate and ammonium phosphate are added into the filtrate, the mass ratio of the lithium iron phosphate to the manganese carbonate is 100:70, and the mass ratio of the lithium iron phosphate to the ammonium phosphate is 100:50, stirred at 55°C for 30 minutes, then adjusted to pH 11 with ammonia water, and continuously stirred at 55°C for 6 hours, filtered, washed, and dried to obtain a solid;

[0064] (5) The solid obtained in step (4), a fullerene trifluoromethyl derivative (C 60 (CF3) 24 ) and polyvinyl alcohol are mixed by grinding, the mass ratio of the solid, the fullerene trifluoromethyl derivative and the polyvinyl alcohol is 100:1.5:4, and then calcined under an argon atmosphere, the calcination process is as follows: heated to 220°C at a rate of 8°C / min, kept for 2 hours, then heated to 330°C at a rate of 2°C / min, kept for 2 hours, and then cooled to obtain an intermediate;

[0065] (6) The intermediate obtained in step (5) is ground and mixed with graphene and glucose, the mass ratio of the intermediate, the graphene and the glucose is 100:1:4, and then calcined under a mixed gas atmosphere of hydrogen and argon (the volume ratio of hydrogen to argon is 1:1), the calcination process is as follows: heated to 400°C at a rate of 6°C / min, kept for 2 hours, then heated to 700°C at a rate of 3°C / min, kept for 4 hours, and then naturally cooled to prepare lithium manganese iron phosphate.

[0066] Comparative Example 1

[0067] Comparative Example 1 is different from Example 1 only in that, in step (5), an equal amount of C 60 is used instead of C 60 (CF3) 24 , and the other processes are the same as those in Example 1.

[0068] Comparative Example 2

[0069] Comparative Example 2 is different from Example 1 only in that, in step (6), an equal amount of carbon nanotubes is used instead of graphene, and the other processes are the same as those in Example 1.

[0070] Comparative Example 3

[0071] The difference between Comparative Example 3 and Example 1 is only that the calcination process of Step (5) of Comparative Example 3 is: heating to 330℃ at a rate of 5℃ / min, keeping for 4 hours, and then cooling to obtain the intermediate, and other processes are the same as those of Example 1.

[0072] Product effect test

[0073] Electrochemical performance test: the lithium manganese iron phosphate prepared in the example or the comparative example is used as a positive electrode material, and is uniformly mixed at a mass ratio of 8:1:1 of the positive electrode material, acetylene black and a binder (PVDF polyvinylidene fluoride), and is grinded to obtain a uniformly mixed slurry by using NMP (N-methyl pyrrolidone) as a solvent. The slurry is coated on an aluminum foil, dried in a vacuum oven at 120℃ for 6 hours, and then cut into a circular sheet with a diameter of 8mm. The circular sheet is assembled into a CR2025 button cell. The button cell is subjected to constant current charge and discharge test at room temperature, with a limited voltage of 2V to 4.1V. The first circle discharge capacity under a test current density of 1C is tested, and the discharge capacity result after 200 cycles is recorded under the test condition. The results are shown in Table 1.

[0074] Table 1

[0075] Item First cycle discharge specific capacity (mAh / g) Discharge specific capacity at 200 cycles (mAh / g) Example 1 162.8 158.6 Example 2 161.1 154.3 Example 3 165.9 162.1 Comparative Example 1 157.6 142.2 Comparative Example 2 149.1 126.9 Comparative Example 3 158.2 132.5

[0076] As can be seen from Table 1, the lithium manganese iron phosphate prepared in Examples 1-3 of the present application is used as a positive electrode material in a battery, and the battery has a high specific discharge capacity, and still maintains a high specific discharge capacity after 200 cycles. Therefore, the lithium manganese iron phosphate prepared in the examples of the present application has good cycle stability when applied in a battery.

[0077] As can be seen from the results of Example 1 and Comparative Examples 1-3, the C 60 (CF3) 24 and graphene cannot be replaced by other raw materials, which may be mainly due to the special electronic properties of C 60 (CF3) 24 and graphene, and the stable coating structure formed on the surface of the lithium manganese iron phosphate. As can be seen from Comparative Example 3, the calcination process also affects the cycle stability of the lithium manganese iron phosphate.

[0078] Figure 1 The discharge cycle curve of the button cell assembled by the lithium manganese iron phosphate prepared in Example 3 of the present application. As can be seen from Figure 1 the discharge cycle curve, the button cell assembled by the lithium manganese iron phosphate prepared in Example 3 of the present application has good cycle stability.

[0079] It has to be noted that, as used herein, such terms as "including", "including a", "having", "comprising", "containing", or any other similar words, are intended to be used inclusively, so that a process, method, article, or apparatus that includes a list of elements is not limited to those elements, but can include other elements not expressly listed or even inherent to such process, method, article, or apparatus.

[0080] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since numerous modifications and changes can be made to the embodiments without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A method for recycling spent lithium iron phosphate battery cathode material to prepare lithium manganese iron phosphate, characterized in that, The method comprises the following steps: (1) obtaining a positive plate from a waste lithium iron phosphate battery; (2) performing heat treatment on the positive plate obtained in step (1) to obtain lithium iron phosphate and aluminum foil; (3) taking the lithium iron phosphate obtained in step (2) and adding it into an inorganic acid to react, and then filtering to obtain a filtrate; (4) taking the filtrate obtained in step (3), adding a manganese source and a phosphorus source into the filtrate, stirring, then adjusting the pH to be alkaline, separating, and drying to obtain a solid; (5) grinding and mixing the solid obtained in step (4), a fullerene trifluoromethyl derivative, and polyvinyl alcohol, performing roasting under a protective gas atmosphere, and then cooling to obtain an intermediate; (6) grinding the intermediate obtained in step (5), mixing it with graphene and glucose, and then performing calcination under a mixed gas atmosphere of hydrogen and a protective gas, and cooling to prepare the lithium manganese iron phosphate; In step (5), the fullerene trifluoromethyl derivative is C 60 (CF3) 24 ; and, in step (5), the process of calcination is: heating at a rate of 5-10 °C / min to 200-250 °C, holding for 1-2 hours, then heating at a rate of 1-4 °C / min to 320-350 °C, holding for 2-4 hours.

2. The method of claim 1, wherein, In step (2), the temperature of the heat treatment is 480-580℃, and the time of the heat treatment is 1.5-2.5 hours.

3. The method of claim 1, wherein, In step (3), the inorganic acid is at least one selected from sulfuric acid, hydrochloric acid, or nitric acid; and / or, in step (3), the temperature of the reaction is 75-100℃, and the time of the reaction is 1-6 hours.

4. The method of claim 1, wherein, In step (3), the amount ratio of the lithium iron phosphate to the inorganic acid is 100g:(300-600)mL; and / or, the concentration of the inorganic acid is 1-5mol / L.

5. The method of claim 1, wherein, In step (4), the manganese source is at least one selected from manganese sulfate, manganese carbonate, or manganese nitrate; and / or, in step (4), the phosphorus source is at least one selected from monobasic ammonium phosphate or ammonium phosphate.

6. The method of claim 1, wherein, In step (4), the mass ratio of the lithium iron phosphate to the manganese source is 100:(50-80); and / or, in step (4), the mass ratio of the lithium iron phosphate to the phosphorus source is 100:(30-70).

7. The method of claim 1, wherein, In step (4), the temperature of the stirring is 45-65℃, and the time of the stirring is 5-10 hours; and / or, in step (5), the mass ratio of the solid, the fullerene trifluoromethyl derivative, and the polyvinyl alcohol is 100:(1-5):(1-12).

8. The method according to any one of claims 1 to 7, characterized in that, In step (6), the mass ratio of the intermediate to the graphene and the glucose is 100:(0.5-4):(1-10).

9. The method according to any one of claims 1-8 for use in the field of batteries.

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