A method for recycling and regenerating waste battery graphite negative electrode and application

Abstract

The application discloses a recycling method and application of waste battery graphite negative electrode, and the recycling method comprises the following steps: pretreating waste battery graphite negative electrode sheets, stripping graphite from the current collector to obtain a graphite mixture; then, performing solid-liquid separation on the graphite mixture, and performing standing precipitation on the separated graphite slurry, and removing part of supernatant to obtain graphite material with a predetermined water content; then, placing the graphite material in a sealed reactor, and performing rotary treatment under a predetermined temperature and a predetermined pressure; and under the predetermined temperature and the predetermined pressure, water contained in the graphite material is converted into superheated water vapor to perform gradient etching modification on the surface of the graphite material, and the graphite negative electrode material is obtained. Compared with the prior art, the method has excellent performance, and the whole process has low energy consumption and no acid and alkali pollution.

Description

Technical Field

[0001] This invention belongs to the field of waste battery recycling technology, and particularly relates to a method and application for recycling and regenerating graphite negative electrodes from waste batteries. Background Technology

[0002] With the explosive growth of the electric vehicle and energy storage markets, the consumption and scrapping of lithium-ion batteries have increased dramatically. Simultaneously, the widespread adoption of new energy vehicles has led to a decline in the proportion of traditional gasoline-powered vehicles, resulting in a corresponding contraction in petroleum demand. In the long term, this will affect the supply of petroleum refining byproducts such as petroleum coke. Graphite, as the primary anode material for lithium-ion batteries, is mainly derived from artificial graphite anodes, typically prepared from petroleum coke and needle coke obtained after crude oil refining. Changes in the supply and demand of petroleum resources will indirectly impact the supply of raw materials for graphite anodes. Therefore, recovering graphite from waste batteries and achieving its high-value reuse is of great significance for ensuring resource security, saving costs, and protecting the environment.

[0003] Currently, the main process for recovering graphite anode materials from spent lithium-ion batteries includes: firstly, separating the graphite active material from the copper foil current collector in the anode sheet. Common separation methods include high-temperature calcination and mechanical crushing and sieving. High-temperature calcination removes the binder at high temperatures, causing the graphite to separate from the copper foil. However, this method is energy-intensive, and the high-temperature environment easily leads to copper oxidation or evaporation, introducing copper impurities that contaminate the graphite. Mechanical crushing and sieving uses physical force to crush the anode sheet, followed by sieving to separate the graphite from the copper foil. However, this method also easily leads to copper foil fragments being mixed in with the graphite powder, introducing metallic foreign matter. The separated graphite powder usually contains residual binders, conductive agents, and metallic impurities such as copper, aluminum, and lithium, requiring further purification. Industrially used purification methods include acid washing and high-temperature graphitization. Pickling uses strong acid immersion to remove metal impurities, but this process generates a large amount of acidic waste liquid, causing secondary pollution. More importantly, if the pickling conditions are not properly controlled, the graphite surface may be over-etched, damaging its crystal structure, resulting in abnormal interlayer spacing and increased lattice defects, which in turn affects the reversible insertion / extraction capability of lithium ions, ultimately leading to a decrease in the battery's first-cycle efficiency. The specific mechanisms include: (1) residual metal impurities or new impurities introduced by pickling will trigger side reactions during charging and discharging, consuming active lithium ions; (2) the damaged graphite crystal structure hinders the smooth insertion and extraction of lithium ions; (3) pickling damages the original solid electrolyte interphase (SEI) film on the graphite surface, and the reformation of an incomplete or unstable SEI film will consume more lithium ions; (4) pickling may abnormally increase the specific surface area of ​​graphite, leading to an increase in the amount of lithium ions required to form the SEI film during the first charge and discharge. To improve the electrochemical performance of graphite after pickling, existing technologies usually require subsequent repair treatment, such as repairing structural defects through heat treatment or surface coating to improve the SEI film formation capability. However, while surface coating can improve initial efficiency, it often reduces the compaction density of the material and may affect the high-temperature cycling performance of the battery.

[0004] Furthermore, to meet the fast-charging requirements of power batteries, graphite anodes often need to undergo fast-charging performance modification. Common methods include reducing particle size, creating pores, surface coating, and etching to increase interlayer spacing. However, each of these methods has its limitations: reducing particle size significantly reduces the compaction density and coating performance of the anode; while coating the graphite surface with soft carbon improves fast-charging performance, it also negatively reduces compaction; traditional pore-creating or etching methods usually require the introduction of external reaction atmospheres or chemical reagents, which are complex, costly, and difficult to precisely control the etching degree, easily leading to uneven or excessive etching, which is detrimental to performance improvement.

[0005] Therefore, in the field of graphite recycling and reuse, there is currently no integrated process that can simultaneously achieve efficient separation, deep purification, structural repair, and performance improvement. Developing a simple, green, and low-cost method that can integrate graphite recycling and performance optimization has become a pressing technical challenge in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method and application for recycling and regenerating graphite anodes from waste batteries, in order to overcome the shortcomings of existing technologies in graphite anode recycling, such as high energy consumption, large pollution, easy damage to the graphite structure during separation and purification processes, and difficulty in simultaneously achieving performance repair and modification. This invention aims to simultaneously achieve the technical effects of efficient recycling, structural repair, and fast-charging performance optimization of graphite anode materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for recycling and regenerating graphite negative electrodes from waste batteries, comprising the following steps:

[0009] S1. Pre-treat the graphite negative electrode sheet of the waste battery to remove the graphite from the current collector and obtain a graphite mixture.

[0010] S2. The graphite mixture in step S1 is subjected to solid-liquid separation, and the separated graphite slurry is allowed to settle and some of the supernatant is removed to obtain graphite material with a predetermined water content.

[0011] S3. Place the graphite material from step S2 in a closed reactor and perform rotation treatment at a predetermined temperature and pressure. At the predetermined temperature and pressure, the moisture contained in the graphite material is converted into superheated steam to perform gradient etching modification on the surface of the graphite material, thereby obtaining the graphite anode material.

[0012] Preferably, in step S1, the pretreatment includes mixing the graphite negative electrode sheet of the waste battery with water and then heating, stirring and ultrasonic treatment; specifically, the mixture is heated to 70~80℃ and reacted at a stirring speed of 100~300 rpm for 1~6 hours, and ultrasonic treatment with a power of 500~600W is applied 1~2 times every 30 minutes during the reaction, and the treatment time is 9~15 minutes.

[0013] Preferably, the predetermined moisture content of the graphite material in step S2 is 100%~200%.

[0014] Preferably, in step S3, the rotation treatment under the predetermined temperature and pressure includes: applying a pressure of 0.5~2.0 MPa to the reactor and controlling the reactor to rotate at a speed of 700~800 rpm for 1~2 hours; reheating and gradually raising the temperature to 650~1000 ℃ for 2~6 hours; after the reaction is completed, gradually cooling down to 200~300 ℃, and then introducing air into the reactor for oxidation etching.

[0015] Preferably, the method further includes step S4: drying and sieving the modified graphite anode material from step S3.

[0016] Preferably, in step S4, the sieving process includes passing the dried powder material through a sieve to obtain the graphite anode material with a particle size of 5μm to 45μm.

[0017] Secondly, the present invention provides a recycled graphite anode material obtained by the above-mentioned recycling method.

[0018] Preferably, the surface of the graphite anode material particles has pits formed by gradient etching modification, and the specific surface area of ​​the graphite anode material is 2.2~3.0 m². 2 / g.

[0019] Preferably, the powder compaction density of the graphite anode material is ≥2.0 g / cm³. 3 ;

[0020] And / or, a lithium-ion battery made using the graphite anode material as the anode active material has a charging capacity retention rate of ≥92% at a 2C rate.

[0021] Thirdly, the present invention provides a lithium-ion battery comprising the above-mentioned recycled graphite anode material.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] This invention places graphite material in a closed reactor and rotates it under predetermined temperature and pressure. The water contained in the graphite material is converted into superheated steam to perform gradient etching modification on the surface of the graphite material. At the same time, organic binders can be removed. This one-step process achieves the purification and recovery of graphite and the modification of its surface microstructure, thereby simplifying the process and reducing energy consumption and cost.

[0024] The gradient etching proposed in this invention ensures a progressive and non-uniform etching process by controlling the rotation of the reactor. This gradient etching not only does not destroy the overall crystal structure of graphite, but also significantly improves the compaction density and lithium-ion migration rate of the material by increasing the contact points between particles and the internal porosity. Furthermore, it further enhances the fast-charging performance of the graphite anode material by constructing rapid lithium-ion transport channels through the micropores and mesopores formed by the instantaneous oxidation during the cooling stage.

[0025] The entire process of this invention uses only water as a medium and does not introduce any acids, alkalis or other harmful chemical reagents. It employs a mild physicochemical synergy to separate graphite and current collector, fundamentally avoiding secondary pollution and conforming to the concepts of green chemistry and sustainable development.

[0026] The graphite material obtained by the recycling method of this invention exhibits a high compaction density (over 2.0 g / cm³ for 5 tons of powder) when used to manufacture new battery anodes due to the optimized surface properties and internal structure. 3 It boasts excellent fast charging performance with high charge / discharge rate capacity retention (up to 92% or more at 2C rate). Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a SEM image of the graphite anode material prepared in Example 1 of the present invention;

[0029] Figure 2 This is a SEM image of the graphite anode material prepared in Comparative Example 6 of this invention. Detailed Implementation

[0030] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0032] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0033] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0034] According to a first aspect of the present invention, the present invention provides a method for recycling and regenerating graphite negative electrodes from waste batteries, comprising the following steps:

[0035] S1. Pre-treat the graphite negative electrode sheet of the waste battery to remove the graphite from the current collector and obtain a graphite mixture.

[0036] S2. The graphite mixture in step S1 is subjected to solid-liquid separation, and the separated graphite slurry is allowed to settle and some of the supernatant is removed to obtain graphite material with a predetermined water content.

[0037] S3. Place the graphite material from step S2 in a closed reactor and perform rotation treatment at a predetermined temperature and pressure. At the predetermined temperature and pressure, the moisture contained in the graphite material is converted into superheated steam to perform gradient etching modification on the surface of the graphite material, thereby obtaining the graphite anode material.

[0038] In some embodiments of the present invention, in step S1, the pretreatment includes mixing the graphite negative electrode sheet of the waste battery with water and then heating, stirring and ultrasonic treatment; specifically, the mixture is heated to 70~80 ℃ and reacted at a stirring speed of 100~300 rpm for 1~6 hours, and ultrasonic treatment with a power of 500~600 W is applied 1~2 times every 30 minutes during the reaction, and the treatment time is 9~15 minutes.

[0039] The pretreatment in step S1 includes heating the mixture to 70-80 °C and reacting it at a stirring speed of 100-300 rpm for 1-6 hours. During the reaction, ultrasonic treatment with a power of 500-600W is applied 1-2 times every 30 minutes for 9-15 minutes. This series of parameter settings is a carefully designed and optimized synergistic process, aiming to maximize the initial separation, interface activation, and impurity loosening of the negative electrode material with minimal physicochemical damage, creating the optimal material state for subsequent deep processing.

[0040] In some embodiments of the present invention, the predetermined moisture content of the graphite material in step S2 is 100% to 200%.

[0041] In step S2, the moisture content of the dehydrated material is precisely controlled between 100% and 200%, for example, it can be 100%, 120%, 140%, 150%, 160%, 180%, or 200%, preferably 150% to 180%. This key parameter setting is based on the following considerations: First, an appropriate amount of moisture can penetrate to the interface between the graphite and the current collector under mechanical action, acting as a lubricant and weakening the adhesion, thereby achieving gentle and complete peeling of the graphite coating and effectively suppressing dust generation. Second, this moisture content range creates a microenvironment conducive to mass transfer and initial cleaning in an aqueous phase. Most importantly, it keeps the material moist before entering the subsequent integrated processing steps, ensuring uniform dispersion and efficient interfacial reaction of graphite particles in the subsequent reaction system, laying the foundation for obtaining high-performance materials. A moisture content below 100% approaches dry peeling, which is ineffective; above 200% leads to viscous materials, increased energy consumption, and decreased economic efficiency.

[0042] In some embodiments of the present invention, step S3, the rotation process under the predetermined temperature and predetermined pressure includes: applying a pressure of 0.5 to 2.0 MPa to the reactor, controlling the reactor to rotate at a speed of 700 to 800 rpm for 1 to 2 hours; reheating and gradually raising the temperature to 650 to 1000 °C for 2 to 6 hours; after the reaction is completed, gradually cooling down to 200 to 300 °C, and then introducing air into the reactor for oxidation etching.

[0043] In the water vapor gradient etching modification process, a pressure of 0.5–2.0 MPa is applied to the reactor, and the reactor is rotated at 700–800 rpm for 1–2 hours. Under the same pressure and rotation speed, the graphite material is heated to 650–1000 °C and reacted for 2–6 hours. After the reaction, the temperature is gradually reduced to 200–300 °C, and then air is introduced into the reactor for a short-term oxidation etching treatment, while simultaneously achieving rapid cooling of the material. Under these conditions, the reactor is started to rotate, causing the graphite material to be in a dynamic tumbling state within the reactor. The moisture inside the material is converted into superheated steam under high temperature and pressure. During the heating stage, this steam performs gradient etching on the surface of the tumbling graphite particles, forming mainly micropores. During the cooling stage, a short-term oxidation etching is performed, forming a small number of larger mesopores. The mechanism is that the difference in instantaneous temperature and pressure when graphite particles come into contact with and collide with hot walls during the tumbling process results in different degrees of etching at different locations on their surface. This non-uniform etching can creatively introduce tiny pits and defects on the surface of graphite particles, increase the effective contact points between graphite particles, and at the same time form a rich micropore and mesopore structure inside the particles.

[0044] In some embodiments of the present invention, step S4 is further included: drying and sieving the modified graphite anode material from step S3.

[0045] In some embodiments of the present invention, in step S4, the sieving process includes passing the dried powder material through a sieve to obtain the graphite anode material with a particle size of 5 μm to 45 μm.

[0046] The dried material is graded through a 325-mesh sieve to ensure that the final graphite anode material has a particle size distribution between 5 μm and 45 μm. This particle size control is a key design feature of this invention: a particle size ≥ 5 μm effectively avoids problems such as excessively large specific surface area, deteriorated compaction density, and difficulties in slurry processing caused by excessively fine particles; a particle size ≤ 45 μm ensures that the solid-phase diffusion path of lithium ions within the particles is not too long, thus guaranteeing the material's excellent fast charge and discharge capabilities. Simultaneously, the sieving process itself is also an efficient purification step, removing any potentially residual trace metal fragments or oversized particle clusters, ensuring product consistency and reliability. This particle size range is related to the core process of this invention—gentle exfoliation and structural protection—achieving a balance between fast charging performance, high energy density, and good processability.

[0047] According to a second aspect of the present invention, the present invention provides a recycled graphite anode material obtained by the above-described recycling method.

[0048] In some embodiments of the present invention, the surface of the graphite anode material particles has pits formed by gradient etching modification, and the specific surface area of ​​the graphite anode material is 2.2~3.0 m². 2 / g.

[0049] In some embodiments of the present invention, the powder compaction density of the graphite anode material is ≥2.0 g / cm³. 3 ;

[0050] And / or, a lithium-ion battery made using the graphite anode material as the anode active material has a charging capacity retention rate of ≥92% at a 2C rate.

[0051] The specific surface area of ​​the graphite anode material was precisely controlled within the range of 2.2 to 3.0 m². 2 The range is [value missing] g. This range ensures that the material has sufficient lithium-ion reactive sites while strictly limiting the initial irreversible lithium loss due to excessive specific surface area. This directly proves that the purification and modification process of this invention effectively avoids excessive surface corrosion, laying the structural foundation for achieving high-rate lithium uptake.

[0052] Among them, the compaction density of the graphite anode material is greater than 2.0 g / cm³. 3 This is significantly superior to conventional recycled materials. This indicates that the material obtained by this invention has complete particle morphology and reasonable particle size distribution, enabling close packing and meeting the stringent requirements of modern lithium-ion batteries for high volumetric energy density.

[0053] Among them, the graphite anode material exhibits a capacity retention rate of ≥92% under 2C high-rate charging conditions. This data comprehensively reflects the material's advantages in crystal structure, interface dynamics, and ion transport pathways, indicating that the present invention not only achieves graphite recycling but also simultaneously endows it with excellent fast-charging capabilities, solving the traditional problem of fast-charging anode material preparation.

[0054] According to a third aspect of the present invention, a lithium-ion battery is provided, comprising a cell wound with a negative electrode sheet, a positive electrode sheet, and a separator, an electrolyte, and a casing for encapsulating the cell and the electrolyte. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising the aforementioned graphite negative electrode material, or comprising the aforementioned recycled graphite negative electrode material.

[0055] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0056] Example 1

[0057] 1) Take 1 kg of graphite negative electrode sheet obtained from dismantling waste lithium iron phosphate batteries and cut it into 5cm×5cm fragments;

[0058] 2) Put the fragments into a reaction vessel equipped with a stirrer and an ultrasonic device, add 5 L of deionized water, and react at 80℃ and 300 rpm for 3 hours. During this period, apply ultrasonic treatment with a power of 500W every 30 minutes for 10 minutes each time.

[0059] 3) After the reaction is complete, filter the copper foil and graphite material through a 200-mesh sieve. Let the graphite material stand and settle for 12 hours. Then, discharge the supernatant into the circulating water tank. The water in the tank is repeatedly circulated back to the reaction tank to obtain a wet graphite filter cake with a water content of 150%.

[0060] 4) Load the wet graphite filter cake into a rotatable high-pressure reactor, seal it, and purge it with nitrogen until the initial pressure is 0.5 MPa. Control the reactor to rotate at 800 rpm for 1 hour. While maintaining this rotation speed, heat the material to 950 ℃ at a rate of 5 ℃ / min. At this point, the pressure inside the reactor rises to 1.2 MPa, and the reaction continues for 4 hours to form powder.

[0061] 5) After the reaction is complete, gradually cool down to 200 ℃, then introduce air into the reactor for a short-term oxidation etching process. After naturally cooling to room temperature and depressurizing, remove the modified graphite.

[0062] 6) After drying the modified graphite, pass it through a 325-mesh sieve and demagnetize it to obtain the final graphite anode material.

[0063] Example 2

[0064] The difference from Example 1 is that the reaction time in step 2) is 2 hours and the wet graphite filter cake with a moisture content of 120% is obtained in step 3). The remaining steps are the same as in Example 1.

[0065] Example 3

[0066] The difference from Example 1 is that the reaction time in step 2) is 4 hours and the wet graphite filter cake with a moisture content of 200% is obtained in step 3). The remaining steps are the same as in Example 1.

[0067] Example 4

[0068] The difference from Example 1 is that in step 4), the temperature is raised to 1000 °C, while the rest of the steps are the same as in Example 1.

[0069] Example 5

[0070] Unlike Example 1, in step 4), the temperature is raised to 1000 °C, at which point the pressure inside the vessel rises to 0.6 MPa. The remaining steps are the same as in Example 1.

[0071] Example 6

[0072] Unlike Example 1, in step 4), the temperature is raised to 1000 °C, at which point the pressure inside the vessel rises to 0.8 MPa. The remaining steps are the same as in Example 1.

[0073] Example 7

[0074] Unlike Example 1, in step 4), the temperature is raised to 1000 °C, at which point the pressure inside the vessel rises to 1.0 MPa. The remaining steps are the same as in Example 1.

[0075] Example 8

[0076] Unlike Example 1, in step 4), the temperature is raised to 900 °C, at which point the pressure inside the vessel rises to 1.0 MPa. The remaining steps are the same as in Example 1.

[0077] Example 9

[0078] Unlike Example 1, in step 4), the temperature is raised to 850 °C, at which point the pressure inside the vessel rises to 1.0 MPa. The remaining steps are the same as in Example 1.

[0079] Example 10

[0080] Unlike Example 1, in step 4), the temperature is raised to 800 °C, at which point the pressure inside the vessel rises to 1.0 MPa. The remaining steps are the same as in Example 1.

[0081] Comparative Example 1

[0082] The difference from Example 1 is that step 2 is omitted, and the remaining steps are the same as in Example 1.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that the wet graphite filter cake with a moisture content of 150% obtained in step 3) is replaced with a wet graphite filter cake with a moisture content of 50%, and the remaining steps are the same as in Example 1.

[0085] Comparative Example 3

[0086] The difference from Example 1 is that step 5 is omitted, and the remaining steps are the same as in Example 1.

[0087] Comparative Example 4

[0088] Unlike Example 1, in step 4), the temperature is raised to 500 °C, at which point the pressure inside the vessel rises to 0.3 MPa. The remaining steps are the same as in Example 1.

[0089] Comparative Example 5

[0090] Unlike Example 1, in step 4), the temperature is raised to 1200 °C, at which point the pressure inside the vessel rises to 3.0 MPa. The remaining steps are the same as in Example 1.

[0091] Comparative Example 6

[0092] The traditional acid washing method was used, but unlike Example 1, the wet graphite filter cake obtained in step 3) was soaked in 1 mol / L dilute hydrochloric acid at 60°C for 4 hours, then washed with water until neutral, and then vacuum dried at 120°C for 12 hours. After being crushed and sieved, the graphite anode material was obtained.

[0093] Comparative Example 7

[0094] Unlike Example 1, the wet graphite filter cake in step 3) was vacuum dried at 120°C for 12 hours, and then pulverized and sieved to obtain the graphite anode material.

[0095] Comparative Example 8

[0096] The recycled electrode sheets were heated by high-temperature calcination and then peeled and screened to obtain graphite anode material.

[0097] Comparative Example 9

[0098] The recycled electrode sheets were crushed and sieved using a pulverizer by mechanical stripping to obtain graphite anode material.

[0099] Materials characterization and battery performance testing

[0100] 1. Material characterization: The specific surface area was determined by nitrogen adsorption (BET); the microstructure of the material was analyzed by scanning electron microscopy (SEM).

[0101] 2. Electrode Preparation and Battery Assembly: The graphite anode materials prepared in the above examples and comparative examples were mixed with sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) at a mass ratio of 96:2:2 to form slurries, which were then coated onto copper foil to prepare anode sheets. Using lithium metal as the counter electrode, CR2032 coin cells were assembled.

[0102] 3. Performance testing: After activation at 0.2C, the battery was charged at 0.5C, 1C, and 2C rates respectively, and then discharged at 0.2C rate. The capacity retention rate was calculated. Other performance tests were conducted according to the testing methods of the lithium battery anode graphite industry. The test results are detailed in Table 1.

[0103] Table 1

[0104]

[0105] As shown in Table 1, the copper and iron impurity content in the graphite anode material obtained by the recycling method of this invention is lower than that of traditional methods, proving that the separation process avoids secondary pollution. The specific surface area of ​​the graphite anode materials in Examples 1-10 is greater than that obtained by acid washing in Comparative Example 6, high-temperature calcination in Comparative Example 8, and mechanical exfoliation in Comparative Example 9. A suitable specific surface area is beneficial for improving the powder compaction density and kinetic properties of graphite. The graphite anode material obtained by the recycling method of this invention is superior to Comparative Examples 6-9 in both compaction density and rate performance. The higher compaction density benefits from the preservation of the particle structure; the excellent rate performance is related to the suitable specific surface area and good surface conductivity.

[0106] Compared to Example 1, Comparative Example 1 did not undergo pretreatment, resulting in insufficient impurity removal from the fragments. The resulting graphite anode material had high copper and iron impurity content, leading to a smaller specific surface area, lower compaction density, and reduced rate cycling performance. Comparative Example 2's graphite slurry had too low a moisture content, failing to effectively form a gradient etching microstructure, resulting in a significant decrease in specific surface area, compaction density, and rate performance. Comparative Example 3 only used steam etching without cooling and instantaneous oxidation, which may not effectively form a gradient pore structure rich in micropores and mesopores, leading to a significant decrease in specific surface area and rate cycling performance. Comparative Example 4 shows that if the temperature and pressure are too low, the moisture in the graphite material itself may not be fully converted into water vapor for gradient etching, resulting in a decrease in the specific surface area, compaction density, and rate cycling performance of the obtained graphite anode material. Comparative Example 5 shows that if the temperature and pressure are too high, the graphite particles may be over-etched, leading to the collapse of the internal structure of the graphite material and a decrease in stability, thus reducing the rate cycling performance. Therefore, when performing surface etching modification on graphite, the temperature and pressure need to be controlled within a suitable range.

[0107] In addition, in comparison Figure 1 and Figure 2 It can be seen that, compared with traditional acid washing and graphite recycling, the graphite anode material recycled and regenerated by this invention can clearly show the tiny pits and rough structure formed on the surface after gradient etching.

[0108] In summary, the method provided by this invention successfully achieves efficient recycling and performance improvement of waste graphite in a green and environmentally friendly manner, resolves many contradictions in the prior art, and produces high-performance recycled materials with broad prospects for industrial application.

[0109] 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, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling and regenerating graphite negative electrodes from waste batteries, characterized in that, Includes the following steps: S1. Pre-treat the graphite negative electrode sheet of the waste battery to remove the graphite from the current collector and obtain a graphite mixture. S2. The graphite mixture from step S1 is subjected to solid-liquid separation, and the separated graphite slurry is allowed to settle and some of the supernatant is removed to obtain graphite material with a predetermined moisture content; wherein, the predetermined moisture content of the graphite material is 100%~200%; S3. Place the graphite material from step S2 in a closed reactor and rotate it under a predetermined temperature and pressure. Under the predetermined temperature and pressure, the water contained in the graphite material is converted into superheated steam to perform gradient etching modification on the surface of the graphite material, thereby obtaining the graphite anode material. The rotation process under the predetermined temperature and pressure includes: applying a pressure of 0.5~2.0MPa to the reactor and controlling the reactor to rotate at a speed of 700~800rpm for 1~2 hours; then heating and gradually raising the temperature to 650~1000℃ for 2~6 hours; after the reaction is completed, gradually cooling down to 200~300℃ and then introducing air into the reactor for oxidation etching.

2. The method for recycling and regenerating graphite negative electrodes from waste batteries according to claim 1, characterized in that, In step S1, the pretreatment includes mixing the graphite negative electrode sheet of the waste battery with water and then heating, stirring and ultrasonic treatment; specifically, the mixture is heated to 70~80℃ and reacted at a stirring speed of 100~300 rpm for 1~6 hours, and ultrasonic treatment with a power of 500~600W is applied 1~2 times every 30 minutes during the reaction, and the treatment time is 9~15 minutes.

3. The method for recycling and regenerating graphite negative electrodes from waste batteries according to claim 1, characterized in that, It also includes step S4: drying and sieving the modified graphite anode material from step S3.

4. The method for recycling and regenerating graphite negative electrodes from waste batteries according to claim 3, characterized in that, In step S4, the sieving process includes passing the dried powder material through a sieve to obtain the graphite anode material with a particle size of 5μm to 45μm.

5. A recycled graphite anode material, characterized in that, Obtained by the recycling and regeneration method according to any one of claims 1 to 4.

6. The recycled graphite anode material according to claim 5, characterized in that, The surface of the graphite anode material particles has pits formed by gradient etching modification, and the specific surface area of ​​the graphite anode material is 2.2~3.0 m². 2 / g.

7. The recycled graphite anode material according to claim 5, characterized in that, The powder compaction density of the graphite anode material is ≥2.0 g / cm³. 3 .

8. A lithium-ion battery, characterized in that: Includes the recycled graphite anode material as described in any one of claims 5 to 7.

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