Method for recovering graphite negative electrode from lithium extraction leaching residue of waste lithium iron phosphate battery and application

Abstract

The invention provides a method for recovering a graphite negative electrode from lithium extraction leaching residue of a waste lithium iron phosphate battery and application, the lithium extraction leaching residue of the waste lithium iron phosphate battery is mixed with concentrated sulfuric acid, and a constant temperature reaction is carried out in a high temperature reaction kettle, so that metal ions in the lithium extraction leaching residue are leached and dissolved in the concentrated sulfuric acid; performing solid-liquid separation to obtain metal ion-containing filtrate and graphite slag; ultrasonically washing the graphite slag with deionized water for multiple times until the graphite slag is neutral, and then drying and crushing to obtain graphite powder; the preparation method comprises the following steps: adding a nitrogen-doped carbon source and absolute ethyl alcohol into graphite powder, uniformly mixing through a ball mill, and drying to obtain a graphite precursor; calcining and regenerating the graphite precursor through a microwave high-temperature furnace to obtain regenerated graphite. Metal ions in the lithium extraction leaching residues are heated and leached through concentrated sulfuric acid, and the graphite residues are subjected to microwave calcination regeneration to obtain regenerated graphite. Graphite is recycled by using the lithium extraction leaching residues of the waste lithium iron phosphate batteries, so that the recycling efficiency of the waste lithium iron phosphate batteries is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery recycling, and specifically relates to a method and application of recycling graphite negative electrodes from lithium extraction leaching residues of waste lithium iron phosphate batteries. Background Art

[0002] When lithium iron phosphate batteries reach the end of their service life, they will inevitably be eliminated. Therefore, the batteries need to be recycled to alleviate environmental problems, recycle precious resources, and achieve green, low-carbon and sustainable development strategies. The recycling of waste lithium iron phosphate batteries in industry mainly focuses on the recycling of positive electrode materials. Positive electrode materials can be recycled into new lithium iron phosphate or various lithium salts. Negative electrode materials are ignored because their added value is lower than that of positive electrode materials. Especially when hydrometallurgical lithium extraction is used to recycle waste lithium iron phosphate batteries, the negative electrode materials become lithium extraction leaching slag with complex metal impurities. Lithium extraction leaching slag is usually treated as solid waste, causing environmental pollution. The most commonly used method for regenerating waste negative electrode graphite in industry is high-temperature graphitization, and its operating temperature is generally between 2500 and 3000°C. The damaged structure can be graphitized again, thereby achieving regeneration. Based on the current problems of large-scale waste of lithium leaching residue from waste lithium iron phosphate batteries and high energy consumption in regenerating waste negative electrodes, a low-energy high-temperature treatment method for recovering graphite negative electrodes from lithium leaching residue from waste lithium iron phosphate batteries is developed, which is of great significance for reducing recycling costs and achieving efficient regeneration of waste negative electrode graphite. Summary of the invention

[0003] The purpose of the present invention is to provide a method and application of recycling graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery. The method uses concentrated sulfuric acid to heat and leach metal ions in lithium leaching residue, and the graphite residue is regenerated by microwave calcination to obtain regenerated graphite. Recycling graphite from lithium leaching residue of waste lithium iron phosphate battery improves the recycling efficiency of waste lithium iron phosphate battery. The specific scheme is as follows:

[0004] According to the first aspect of the present invention, one or more embodiments of the present application provide a method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery, which comprises:

[0005] Step 1: mixing the lithium leaching residue of waste lithium iron phosphate battery with concentrated sulfuric acid, and reacting them at a constant temperature in a high-temperature reactor, so that the metal ions in the lithium leaching residue are leached and dissolved in the concentrated sulfuric acid, and the solid-liquid separation is performed to obtain a metal ion-containing filtrate and graphite slag;

[0006] Step 2: The graphite slag is ultrasonically washed with deionized water for multiple times until it becomes neutral, and then dried and crushed to obtain graphite powder;

[0007] Step 3, adding nitrogen-doped carbon source and anhydrous ethanol to graphite powder, mixing them evenly by ball mill, and drying to obtain a graphite precursor;

[0008] Step 4: The graphite precursor is calcined and regenerated in a microwave high-temperature furnace to obtain regenerated graphite.

[0009] According to the above technical solution of the present invention, the following improvements can also be made:

[0010] Wherein, in the step 1, the amount of concentrated sulfuric acid used is 1 to 2 times the mass of the lithium leaching residue.

[0011] Wherein, in the step 1, the solid-to-liquid ratio of the lithium leaching residue from the waste lithium iron phosphate battery to the concentrated sulfuric acid is 10 to 50%.

[0012] Wherein, in the step 1, the reaction temperature in the high temperature reactor is 150-250° C., and the temperature holding time is 120-240 min.

[0013] Wherein, the number of times of ultrasonic washing is 5 to 10 times.

[0014] Wherein, the nitrogen-doped carbon source includes at least one of glucosamine, glucosamine sulfate, and glucosamine hydrochloride.

[0015] Wherein, the addition amount of the nitrogen-doped carbon source is 2-10% of the mass of the graphite powder.

[0016] The microwave high temperature furnace calcination temperature is 500-1000° C., and the temperature holding time is 2-6 hours.

[0017] According to the second aspect of the present invention, one or more embodiments of the present application provide a graphite obtained by any one of the above methods for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate batteries.

[0018] Among them, the obtained graphite is used as the negative electrode material of lithium iron phosphate battery.

[0019] The beneficial effects of the present invention are:

[0020] Compared with the prior art, the present invention provides a method and application for recycling graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery, wherein metal ions in lithium leaching residue of waste lithium iron phosphate battery are leached out by concentrated sulfuric acid at high temperature, and graphite residue is subjected to nitrogen doping carbon coating and microwave calcination to regenerate graphite material by low energy consumption high temperature treatment method. Lithium leaching residue of waste lithium iron phosphate battery is fully utilized, the recycling efficiency of waste lithium iron phosphate battery is improved, and the recycling cost of graphite material is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a flow chart of a method for recovering graphite negative electrodes from lithium leaching residues from waste lithium iron phosphate batteries.

[0022] Figure 2 The invention discloses an XRD diagram of regenerated graphite in a method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate batteries. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0024] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present application should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in one or more embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "including" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] As attached Figure 1-Figure 2 As shown, this embodiment provides a method and application of recycling graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery, the method comprising the following steps:

[0026] (1) The lithium leaching residue of the waste lithium iron phosphate battery is uniformly mixed with an appropriate amount of concentrated sulfuric acid in a beaker, and a high-temperature reactor is used for constant temperature reaction, so that all metal ions in the lithium leaching residue are leached and dissolved in the concentrated sulfuric acid, and solid-liquid separation is performed to obtain a metal ion-containing filtrate and graphite slag;

[0027] (2) recovering valuable metals from the metal ion-containing filtrate obtained in step (1) by other methods, and washing the graphite slag obtained in step (1) with deionized water ultrasonically for multiple times until it becomes neutral, and then drying and pulverizing to obtain graphite powder;

[0028] (3) adding an appropriate amount of nitrogen-doped carbon source and anhydrous ethanol to the graphite powder obtained in step (2), mixing them evenly by a ball mill, and vacuum drying to obtain a graphite precursor;

[0029] (4) placing the graphite precursor obtained in step (3) in a microwave high-temperature furnace and regenerating by microwave calcination to obtain regenerated graphite.

[0030] The method for recycling graphite negative electrode from lithium leaching residue of waste lithium iron phosphate batteries uses concentrated sulfuric acid to leach metal ions at high temperature, cleans the graphite residue, nitrogen-dopes carbon, and microwaves to regenerate graphite materials. The method makes full use of lithium leaching residue from waste lithium iron phosphate batteries and improves the recycling efficiency of waste lithium iron phosphate batteries.

[0031] Furthermore, the amount of concentrated sulfuric acid used in step (1) is 1 to 2 times the mass of the lithium leaching residue; preferably 1.2 to 1.5 times. The solid-liquid ratio of the concentrated sulfuric acid acid leaching process in step (1) is 10 to 50%; preferably 20 to 30%. The temperature of the high-temperature reactor in step (1) is 150 to 250°C; preferably 200 to 220°C. The temperature holding time of the high-temperature reactor in step (1) is 120 to 240 minutes; preferably 150 to 200 minutes. The number of ultrasonic washings in step (2) is 5 to 10 times; preferably 7 to 9 times. The nitrogen-doped carbon source in step (3) includes at least one of glucosamine, glucosamine sulfate, glucosamine hydrochloride, etc. The amount of nitrogen-doped carbon source added in step (3) is 2 to 10% of the mass of graphite powder; preferably 4 to 6%. In the ball milling mixing described in step (3), the speed of the ball mill is 400-500r / s; preferably 450-500r / s. In the ball milling mixing described in step (3), the ball milling time of the ball mill is 60-180min; preferably 150-180min. In the microwave high temperature furnace calcination temperature described in step (4) is 500-1000°C; preferably 700-900°C. In the microwave high temperature furnace calcination temperature holding time described in step (4) is 2-6h; preferably 3-4h.

[0032] Embodiment 1

[0033] (1) Weigh 200 g of dried waste lithium iron phosphate battery lithium leaching residue and 300 g of concentrated sulfuric acid in a beaker, stir evenly, place in a high-temperature reactor for constant temperature reaction, set the temperature to 200 ° C, maintain for 150 min, and naturally cool to room temperature;

[0034] (2) after the reaction is completed, all metal ions in the lithium leaching residue are leached and dissolved in concentrated sulfuric acid, and a vacuum pump is used to filter to obtain a metal ion-containing filtrate and graphite slag;

[0035] (3) The valuable metals in the metal ion-containing filtrate are recovered by other methods, and the graphite slag is ultrasonically washed with deionized water for 10 times, using 500 ml of deionized water each time, until it is neutral;

[0036] (4) drying the graphite in a vacuum drying oven at 100° C. for 12 h to obtain a block of graphite, and crushing the block of graphite using a crusher to obtain graphite powder;

[0037] (5) Weigh 20 g of graphite powder, add 1 g of glucosamine and 70 ml of anhydrous ethanol, set the ball mill speed to 500 r / min, the operation time to 120 min, ball mill uniformly mix, and then dry in a vacuum drying oven set at 100 ° C to obtain a graphite precursor;

[0038] (6) placing the graphite precursor in a microwave high temperature furnace, setting the calcination temperature of the microwave high temperature furnace to 800° C., and the insulation time to 4 h, and obtaining regenerated graphite by microwave calcination regeneration.

[0039] (7) The fixed carbon, volatile matter, moisture and sulfur contents of the regenerated graphite were tested. The test results are shown in Table 1.

[0040] in Figure 2 This is the XRD test diagram of the regenerated graphite obtained in Example 1.

[0041] Table 1

[0042] Fixed carbon % Volatile matter% Moisture% Sulfur content% Embodiment 1 96 ≤1.00 ≤0.2 ≤1.50 Embodiment 2 95 ≤1.00 ≤0.2 ≤1.50

[0043] Embodiment 2

[0044] (1) Weigh 200 g of dried waste lithium iron phosphate battery lithium leaching residue and 250 g of concentrated sulfuric acid in a beaker, stir evenly, place in a high temperature reactor for constant temperature reaction, set the temperature to 180° C., maintain for 180 min, and cool naturally to room temperature;

[0045] (2) after the reaction is completed, all metal ions in the lithium leaching residue are leached and dissolved in concentrated sulfuric acid, and a vacuum pump is used to filter to obtain a metal ion-containing filtrate and graphite slag;

[0046] (3) The valuable metals in the metal ion-containing filtrate are recovered by other methods, and the graphite slag is ultrasonically washed with deionized water for 7 times, using 1000 ml of deionized water each time, until it is neutral;

[0047] (4) drying the graphite in a vacuum drying oven at 100° C. for 12 h to obtain a block of graphite, and crushing the block of graphite using a crusher to obtain graphite powder;

[0048] (5) Weigh 20 g of graphite powder, add 0.8 g of glucosamine and 65 ml of anhydrous ethanol, set the speed of the ball mill to 480 r / min, the operation time to 150 min, ball mill uniformly mix, and dry in a vacuum drying oven set at 100 ° C to obtain a graphite precursor;

[0049] (6) placing the graphite precursor in a microwave high temperature furnace, setting the calcination temperature of the microwave high temperature furnace to 900° C., and the heat preservation time to 3 h, and obtaining regenerated graphite by microwave calcination regeneration.

[0050] (7) The fixed carbon, volatile matter, moisture and sulfur contents of the regenerated graphite were tested. The test results are shown in Table 1.

[0051] One or more embodiments of the present application provide a graphite obtained by any one of the above methods for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate batteries.

[0052] In the embodiment, the obtained graphite can also be used as a negative electrode material for a lithium iron phosphate battery.

[0053] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0054] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery, characterized in that: The steps include: Step 1: mixing the lithium leaching residue of waste lithium iron phosphate battery with concentrated sulfuric acid, and reacting them at a constant temperature in a high-temperature reactor, so that the metal ions in the lithium leaching residue are leached and dissolved in the concentrated sulfuric acid, and the solid-liquid separation is performed to obtain a metal ion-containing filtrate and graphite slag; Step 2: The graphite slag is ultrasonically washed with deionized water for multiple times until it becomes neutral, and then dried and crushed to obtain graphite powder; Step 3, adding nitrogen-doped carbon source and anhydrous ethanol to graphite powder, mixing them evenly by ball mill, and drying to obtain a graphite precursor; Step 4: The graphite precursor is calcined and regenerated in a microwave high-temperature furnace to obtain regenerated graphite.

2. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 1, characterized in that: In the step 1, the amount of concentrated sulfuric acid used is 1 to 2 times the mass of the lithium leaching residue.

3. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 2, characterized in that: In the step 1, the solid-to-liquid ratio of the lithium leaching residue from the waste lithium iron phosphate battery to the concentrated sulfuric acid is 10-50%.

4. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 3, characterized in that: In the step 1, the reaction temperature in the high temperature reactor is 150-250° C., and the temperature is maintained for 120-240 min.

5. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 1, characterized in that: The ultrasonic washing is performed 5 to 10 times.

6. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 1, characterized in that: The nitrogen-doped carbon source includes at least one of glucosamine, glucosamine sulfate, and glucosamine hydrochloride.

7. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 6, characterized in that: The added amount of the nitrogen-doped carbon source is 2-10% of the mass of the graphite powder.

8. A method for recovering graphite negative electrode from lithium leaching residue of waste lithium iron phosphate battery as claimed in claim 1, characterized in that: The microwave high temperature furnace calcination temperature is 500-1000° C., and the temperature holding time is 2-6 hours.

9. A graphite characterized by: The method for recovering graphite negative electrode by extracting lithium from leaching residue of waste lithium iron phosphate batteries as described in any one of claims 1 to 8 is obtained.

10. A graphite as claimed in claim 9, characterized in that: The obtained graphite is used as the negative electrode material of lithium iron phosphate batteries.

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