Method for modifying graphite powder material recovered from lithium battery negative electrodes

Abstract

This invention discloses a method for modifying graphite powder recovered from lithium battery anodes, relating to the field of lithium battery energy recovery and reuse technology. The method involves recovering graphite anode powder, which is then treated by soaking it in a mixture of diethylenetriamine, fatty acids, and ammonia. When graphite and asphalt are mixed, this process significantly reduces the surface tension of water, lowers the free energy at the asphalt-water interface, and creates a uniform and stable emulsion. This allows for better bonding between graphite and asphalt. Furthermore, soft carbon coating modifies and repairs surface defects in the graphite, reducing the specific surface area of ​​the graphite material, thereby increasing capacity and improving cycle dynamics performance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery energy recovery and reuse technology, and in particular to a method for modifying graphite powder for recovering lithium battery negative electrodes. Background Technology

[0002] Lithium-ion batteries are currently the most technologically mature and widely used type of new energy battery. Their superior chemical properties have been widely accepted by developers and users, including no memory effect, high capacity, and good stability. These batteries are used in new energy vehicles and various smart electronic products. Approximately 80% of the negative electrodes in lithium-ion batteries used in the market are made of graphite. Graphitized products are not only expensive and consume a lot of electricity, but also have a certain negative impact on the environment. Conventional graphite recycling processes are highly polluting and expensive, and the processes need optimization. Therefore, finding better ways to recycle and reuse graphite resources is urgently needed.

[0003] Conventional recycled graphite is obtained through processes such as electrode crushing, ultrasonication, acid leaching, sieving, and high-temperature baking. It generally suffers from problems such as large surface defects, large specific surface area, many side reactions, low capacity, low compaction, easy water loss during high-temperature cycling, and poor high-temperature storage capacity.

[0004] Currently, modifying and improving the surface of recycled graphite to reduce its specific surface area and enhance its kinetic properties is a pressing issue. Therefore, this invention proposes a method for modifying graphite powder recovered from lithium-ion battery anodes. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes a method for modifying graphite powder used in the recovery of lithium battery negative electrodes.

[0006] This invention proposes a method for modifying graphite powder recovered from lithium battery anodes, comprising the following steps:

[0007] S1. The recovered graphite powder is leached with hydroiodic acid and a reducing agent. The leaching process is ultrasonically treated to obtain leachate and leaching residue.

[0008] S2. The leaching residue is purified at high temperature under nitrogen protection to form purified graphite powder.

[0009] S3. Place the purified graphite powder into a mixture of diethylenetriamine, fatty acid and ammonia, stir, wash and dry.

[0010] S4. The dried graphite is mixed with asphalt, ball-milled and coated, and then carbonized under inert gas protection to obtain the modified recycled graphite anode material.

[0011] Preferably, the graphite anode recovered in S1 is artificial graphite powder with a particle size of 10-20μm and a specific surface area of ​​less than 2m2 / g. The graphite powder is obtained by processing graphite anode sheets that have never been intercalated with lithium. The electrode sheets come from electrode sheets that were scrapped during coating and rolling processes in the battery cell production process.

[0012] Preferably, the reducing agent in S1 is sodium sulfite or potassium sulfite; the concentration of sodium sulfite or potassium sulfite is 30-90 g / L, the concentration of hydroiodic acid is 3-9 mol / L, the leaching temperature is 50-85℃, the solid-liquid ratio is 2:11-2:33, the leaching time is 3-14 h, and the ultrasonic working time is 3-7 h.

[0013] Preferably, the purification temperature in S2 is 1300-1500℃.

[0014] Preferably, the mass ratio of diethylenetriamine, fatty acid and ammonia in S3 is 6:2:1-2:6:1, i.e. 2-6:2-6:1, in which the proportions are 2-6 for diethylenetriamine, 2-6 for fatty acid and 1 for ammonia.

[0015] Preferably, the ratio of graphite to bitumen in S4 is 0.03:1-0.06:1, the carbonization temperature is 1200-1400℃, and the treatment time is 3-6h.

[0016] The method for modifying graphite powder recovered from lithium battery anodes proposed in this invention has the following beneficial technical effects:

[0017] This method recovers graphite anode powder, which is then treated by soaking it in a mixture of diethylenetriamine, fatty acids, and ammonia. When graphite and asphalt are mixed, this treatment significantly reduces the surface tension of water and the free energy at the asphalt-water interface, resulting in a uniform and stable emulsion. This allows the graphite to better bond with the asphalt. Furthermore, soft carbon coating modifies and repairs the surface defects of the graphite, reducing the specific surface area of ​​the graphite material, thereby increasing its capacity and improving its cycle dynamics performance.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1 The graph shows the electrical performance test data of the button cell made from recycled and modified graphite according to this invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Specific Implementation Example 1

[0022] S1 leaches the recovered artificial graphite powder with hydroiodic acid and sodium sulfite, with a hydroiodic acid concentration of 7 mol / L and a sodium sulfite concentration of 90 g / L. The leaching time is 8 h, and ultrasonic treatment is performed for 10 h to obtain leachate and leaching residue.

[0023] S2 purifies the leaching residue by heating it in a tubular furnace at a temperature of 1300℃;

[0024] S3. Diethylenetriamine, fatty acids, and ammonia are mixed in a mass ratio of 6:2:1. The purified graphite from step S2 is then placed into the mixture of diethylenetriamine, fatty acids, and ammonia, stirred, washed, and dried.

[0025] S4. The dried graphite from step S3 is mixed with asphalt at a ratio of 0.06:1. The mixture is ball-milled and coated in a ball mill, and then carbonized in a tube furnace under inert gas protection to obtain modified recycled graphite anode material. Specific Implementation Example 2

[0027] S1 leaches the recovered artificial graphite powder with hydroiodic acid and sodium sulfite, with a hydroiodic acid concentration of 7 mol / L and a sodium sulfite concentration of 90 g / L. The leaching time is 8 h, and ultrasonic treatment is performed for 10 h to obtain leachate and leaching residue.

[0028] S2 purifies the leaching residue by heating it in a tubular furnace at a temperature of 1300℃;

[0029] S3. Diethylenetriamine and fatty acids are mixed at a mass ratio of 6:2. The purified material from step S2 is then placed into the mixture of diethylenetriamine and fatty acids, stirred, washed, and dried.

[0030] S4. The dried graphite from step S3 is mixed with asphalt at a ratio of 0.06:1. The mixture is ball-milled and coated in a ball mill, and then carbonized in a tube furnace under inert gas protection to obtain modified recycled graphite anode material. Specific Implementation Example 3

[0032] S1 leaches the recovered artificial graphite powder with hydroiodic acid and sodium sulfite, with a hydroiodic acid concentration of 7 mol / L and a sodium sulfite concentration of 90 g / L. The leaching time is 8 h, and ultrasonic treatment is performed for 10 h to obtain leachate and leaching residue.

[0033] S2 purifies the leaching residue by heating it in a tubular furnace at a temperature of 1300℃;

[0034] S3. Mix diethylenetriamine and ammonia water at a mass ratio of 6:1. Put the purified material from step S2 into the mixture of diethylenetriamine and ammonia water, stir, wash, and dry.

[0035] S4. The dried graphite from step S3 is mixed with asphalt at a ratio of 0.06:1. The mixture is ball-milled and coated in a ball mill, and then carbonized in a tube furnace under inert gas protection to obtain modified recycled graphite anode material. Specific Implementation Example 4

[0037] S1 leaches the recovered artificial graphite powder with hydroiodic acid and sodium sulfite, with a hydroiodic acid concentration of 7 mol / L and a sodium sulfite concentration of 90 g / L. The leaching time is 8 h, and ultrasonic treatment is performed for 10 h to obtain leachate and leaching residue.

[0038] S2 purifies the leaching residue by heating it in a tubular furnace at a temperature of 1300℃;

[0039] S3. The purified material from step S2 is placed in diethylenetriamine, stirred, washed, and dried.

[0040] S4. The dried graphite from step S3 is mixed with asphalt at a ratio of 0.06:1. The mixture is ball-milled and coated in a ball mill, and then carbonized in a tube furnace under inert gas protection to obtain modified recycled graphite anode material. Specific Implementation Example 5

[0042] S1 leaches the recovered artificial graphite powder with hydroiodic acid and sodium sulfite, with a hydroiodic acid concentration of 7 mol / L and a sodium sulfite concentration of 90 g / L, for a leaching time of 8 h, followed by ultrasonic treatment for 10 h to obtain leachate and leaching residue.

[0043] S2 purifies the leaching residue by heating it in a tubular furnace at a temperature of 1300℃;

[0044] S3 mixes the purified graphite from step S2 with asphalt at a ratio of 0.06:1, ball-mills the mixture in a ball mill, and then carbonizes it in a tube furnace under inert gas protection to obtain modified recycled graphite anode material.

[0045] Examples 1-4 were prepared into button cells in a laboratory glove box according to a ratio of active material: binder: conductive agent = 8:1:1. Capacity and first-efficiency were observed. Figure 1 As shown, the capacity efficiency of Specific Embodiment 1 is optimal.

[0046] This method for recovering graphite anode powder yields graphite powder with magnetic foreign matter content below 1000 pbb. After soaking in a mixture of diethylenetriamine, fatty acids, and ammonia, the powder significantly reduces the surface tension of water during graphite-asphalt mixing, lowering the free energy at the asphalt-water interface and creating a uniform and stable emulsion. This allows for better bonding between graphite and asphalt, acting as an asphalt emulsifier (surfactant) and CN functional group. Further soft carbon coating modifies the graphite surface defects, reducing the specific surface area of ​​the graphite material, thereby increasing capacity and improving cycle dynamics performance, resulting in a high-performance, cost-effective recycled graphite material.

[0047] The purpose of this invention is to address the shortage of lithium battery materials by proposing a method for modifying graphite powder recycled from lithium battery anodes. This method achieves environmental protection while simultaneously enabling the recycling of high-purity and high-performance graphite in the treatment of solid waste such as lithium battery anode materials.

[0048] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0049] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for modifying a graphite powder recovered from a lithium battery negative electrode, characterized in that, Includes the following steps: S1. The recovered graphite powder is leached with hydroiodic acid and a reducing agent. The leaching process is ultrasonically treated to obtain leachate and leaching residue. The reducing agent in S1 is sodium sulfite or potassium sulfite. S2. The leaching residue is purified at high temperature under nitrogen protection to form purified graphite powder. S3. Place the purified graphite powder into a mixture of diethylenetriamine, fatty acid and ammonia, stir, wash and dry. S4. The dried graphite is mixed with asphalt, ball-milled and coated, and then carbonized under inert gas protection to obtain the modified recycled graphite anode material. The mass ratio of diethylenetriamine, fatty acids and ammonia in S3 is 6:2:1 to 2:6:

1.

2. The method for modifying graphite powder recovered from lithium battery negative electrode according to claim 1, characterized in that, The graphite negative electrode recovered in S1 is artificial graphite powder with a particle size of 10-20μm and a specific surface area of ​​less than 2m2 / g.

3. The method for modifying graphite powder recovered from lithium battery negative electrode according to claim 1, characterized in that, The concentration of sodium sulfite or potassium sulfite is 30-90 g / L, the concentration of hydroiodic acid is 3-9 mol / L, the leaching temperature is 50-85℃, the solid-liquid ratio is 2:11-2:33, the leaching time is 3-14 h, and the ultrasonic working time is 3-7 h.

4. The method for modifying graphite powder recovered from lithium battery negative electrode according to claim 1, characterized in that, The purification temperature of S2 is 1300-1500℃.

5. The method for modifying graphite powder recovered from lithium battery negative electrode according to claim 1, characterized in that, The ratio of graphite to bitumen in S4 is 0.03:1-0.06:1, the carbonization temperature is 1200-1400℃, and the treatment time is 3-6 hours.

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