Spent battery graphite-based recycled active material and preparation and application thereof

Abstract

This invention belongs to the field of waste battery recycling, specifically relating to a method for preparing graphite-based regenerated active materials from waste batteries. The method involves first treating waste graphite material stripped from waste batteries in an oxidizing atmosphere to obtain a first-stage gas-phase material; then treating the first-stage material in an oxidizing acidic solution to obtain a second-stage liquid-phase material; finally treating the second-stage material in a halogen-containing atmosphere at a temperature above 2000°C to obtain a third-stage gas-phase material; and finally treating the third-stage material in a modified solution containing a niobium source, a titanium source, and an additive to obtain a fourth-stage solvothermal treatment. The additive is at least one of ammonium fluoride, ammonium chloride, cyanamide, and urea. The fourth-stage material is then carbon-coated to obtain the aforementioned graphite-based regenerated active material from waste batteries. This invention also includes the materials obtained by the method and their applications. The regenerated material obtained by the method of this invention can simultaneously achieve excellent low-temperature and fast-charging performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode materials, and discloses a method for preparing a low-temperature and fast-charging anode for lithium-ion batteries using waste graphite, as well as the anode material. Background Technology

[0002] In recent years, with the development of new energy vehicles and energy storage industries, the shipment volume of lithium-ion batteries has been increasing. As a result, more and more waste graphite is generated during the lithium-ion battery manufacturing process. At the same time, lithium-ion batteries are gradually entering a retirement boom, and more and more waste graphite is entering the market, which urgently needs high-value treatment and application.

[0003] The main approaches to recycling graphite from waste batteries currently focus on purification and carbon coating. For example, Chinese patent document CN117623301A discloses a method for recycling graphite anodes from waste lithium-ion batteries. This method includes pre-treating the waste lithium-ion batteries to obtain anode material powder, heat-treating the powder to oxidize metallic impurities, then leaching the heat-treated graphite anode material using a deep eutectic solvent composed of choline chloride and glucose. After the leaching reaction, the solid obtained from solid-liquid separation is washed with the same deep eutectic solvent, and then the washed solid material is directly placed in an inert atmosphere for heat treatment and carbonization to obtain recycled graphite anode material. This technology uses a deep eutectic solvent for purification and carbon composite, followed by subsequent carbonization to achieve carbon coating. However, this technical solution struggles to deeply optimize the physicochemical structure of waste graphite and fully utilize its advanced properties.

[0004] For example, Chinese patent document CN118851167A discloses a method for regenerating and repairing graphite after wet lithium extraction from waste lithium batteries. The specific steps are as follows: The graphite residue after wet lithium extraction is crushed into powder and immersed in a sodium hydroxide solution for stirring and washing; the graphite powder washed in step one (alkali washing) is added to a hydrochloric acid solution for stirring and leaching; the graphite powder washed in step two (acid washing) is added to hydrochloric acid, sulfuric acid, and hydrogen peroxide for leaching and drying under ultrasonic conditions; the dried graphite powder is loaded into a ceramic boat and calcined in a tube furnace to obtain graphite. This technical solution achieves graphite purification based on a dual mechanism of alkali followed by acid, which can effectively purify the graphite, but it is still difficult to achieve deep performance optimization.

[0005] In summary, existing purification-carbon coating methods for waste graphite can purify and repair the damaged graphite structure to a certain extent, but existing processing methods are difficult to deeply optimize the physicochemical structure of graphite and make it suitable for applications under low temperature and fast charging conditions. Summary of the Invention

[0006] To address the challenges of existing waste graphite material recycling processes in achieving deep optimization of graphite physicochemical structure and obtaining graphite anode materials that meet both low-temperature and fast-charging requirements, the primary objective of this invention is to provide a method for preparing graphite-based recycled active materials from waste batteries, aiming to recycle graphite anode active materials that combine excellent low-temperature stability and fast-charging performance.

[0007] The second objective of this invention is to provide a graphite-based recycled active material for waste batteries prepared by the aforementioned method and its applications.

[0008] A third objective of this invention is to provide a secondary battery comprising the graphite-based recycled active material from the waste battery.

[0009] The preparation method of graphite-based recycled active material from waste batteries involves pre-treating the waste graphite material stripped from waste batteries in an oxidizing atmosphere to obtain a first-stage gas phase treatment. The first stage material is placed in an acidic treatment solution with oxidizing properties for a second stage of liquid phase treatment to obtain the second stage material; The second-stage material is placed in a halogen-containing atmosphere and subjected to a third-stage gas phase treatment at a temperature above 2000℃ to obtain the third-stage material. The three-stage material is then placed in a modified liquid containing niobium source, titanium source and additives for a fourth stage of solvothermal treatment to obtain a four-stage material; the additives are at least one of ammonium fluoride, ammonium chloride, cyanamide and urea; The graphite-based recycled active material from waste batteries is obtained by coating the four sections of material with carbon.

[0010] This invention innovatively employs a multi-stage gas-liquid-gas-liquid combined treatment process, consisting of a first gas phase, a second liquid phase, a third gas phase, and a fourth liquid phase. Furthermore, by coordinating the control of the composition and conditions at each stage of the treatment, synergistic effects can be achieved. This process effectively and deeply removes harmful impurities, deeply repairs damaged physicochemical structures, and reconstructs ion and electron conduction networks. Consequently, it facilitates the preparation of regenerable materials that combine excellent low-temperature stability with fast-charging performance.

[0011] In this invention, the waste battery can be any waste battery containing graphite material and having economic value from graphite recycling, such as at least one of waste lithium-ion batteries and waste sodium-ion batteries.

[0012] In this invention, the graphite content in the waste graphite material is above 80 wt.%, and can be further 85~98 wt.%.

[0013] In this invention, waste graphite materials are pre-treated in an oxidizing atmosphere to allow for gas-solid processing. This facilitates integration with subsequent processes, optimizes the physicochemical structure of graphite, and improves the low-temperature and fast-charging performance of recycled graphite materials.

[0014] In this invention, the oxidizing atmosphere can be any atmosphere containing oxygen. For example, it can be air, or a mixture of oxygen and a protective atmosphere. The protective atmosphere can be, for example, nitrogen, carbon dioxide, an inert gas, etc.

[0015] In this invention, the temperature of the first stage of gas phase treatment is 300~500℃, and can be further 350~450℃.

[0016] In this invention, the time for the first stage of gas phase treatment is 1 to 5 hours, and can be further 2 to 4 hours.

[0017] In this invention, after the first stage of gas phase treatment, a shaping and grading process can be performed to obtain a first-stage material.

[0018] In this invention, the D50 of the first section of material is controlled to be 6~8μm.

[0019] In this invention, after the first stage of processing, the material can be placed in the acidic treatment solution for a second stage of solid-liquid modification treatment. This facilitates integration with subsequent processes, optimizes the physicochemical structure of graphite, and thus improves the low-temperature and fast-charging performance of recycled graphite materials.

[0020] In this invention, the acidic treatment solution can be any acidic solution with oxidizing properties, such as a nitric acid solution. Preferably, the acidic treatment solution can be a mixed aqueous solution containing an acid and an oxidant. Research in this invention shows that performing the second-stage liquid-phase treatment under the preferred system can further synergistically optimize the physicochemical structure of graphite, contributing to further improvement in the low-temperature and fast-charging performance of recycled graphite materials.

[0021] In this invention, the acid is an inorganic strong acid, preferably at least one of hydrochloric acid and sulfuric acid.

[0022] In this invention, the oxidant is at least one of hypochlorite, water-soluble Fe(III) salt (such as FeCl3), water-soluble Sn(IV) salt (such as SnCl4), perchloric acid, perchlorate, oxygen, oxygen-enriched air, and ozone; it can also be a mixed solution of hydrochloric acid and perchloric acid.

[0023] In this invention, the acid concentration in the acidic treatment solution is 1-20 wt%; the oxidant concentration is 2-30 wt%; the acid concentration is 5-20 wt%; and the oxidant concentration is 10-25 wt%.

[0024] In this invention, the mass ratio of the primary material to the acidic treatment solution is 1:2 to 11, and considering cost, it can be further reduced to 1:3 to 5.

[0025] In this invention, the temperature of the second liquid phase treatment stage is 30~100℃, and can be further 60~90℃.

[0026] In this invention, the time for the second stage of liquid phase treatment is 5~20h, more specifically 8~15h, or even more specifically 8~12h.

[0027] In this invention, after the second stage of liquid phase treatment, the material undergoes solid-liquid separation, water washing, and drying to obtain the second-stage material.

[0028] In this invention, the two-stage material is modified in the halogen-containing atmosphere and at the specified temperature, which helps to further optimize the physicochemical characteristics of waste graphite and further improve the low-temperature and fast-charging performance of recycled materials.

[0029] In this invention, the halogen source in the halogen-containing atmosphere can be at least one of elemental halogens and halogenated hydrocarbon gases; preferably chlorine.

[0030] In this invention, the temperature of the third gas phase treatment stage is 2000~3300℃, and can be further 2600~3000℃.

[0031] In this invention, in order to reduce the amount of halogen-containing atmosphere used, the halogen-containing atmosphere can be introduced after the system temperature reaches the third stage gas phase treatment temperature (that is, the heat preservation stage).

[0032] In this invention, the time for the third stage of gas phase treatment is 5~72h, and can be further 8~20h.

[0033] Preferably, the halogen-containing atmosphere is a mixture of chlorine and haloalkane gases, and more specifically, the volume ratio of the two can be 0.5 to 2:1. Studies have shown that the combination of the preferred halogen-containing atmosphere can further enhance the cryogenic performance of the recycled materials and improve the balance between low temperature and first-efficiency performance.

[0034] In this invention, the haloalkane is, for example, at least one of halomethane and haloethane. The halogen in the haloalkane can be at least one of Cl and F.

[0035] In this invention, the three-stage material is innovatively placed in the special modified liquid for solvothermal treatment. This facilitates combination with other processes to further optimize the physicochemical characteristics of waste graphite and helps to further improve the low-temperature and fast-charging performance of recycled materials.

[0036] In this invention, the niobium source in the modified liquid is at least one of niobium pentachloride, niobium trichloride, niobium fluoride, niobium bromide, and niobium iodide.

[0037] In this invention, the titanium source is a titanate ester; for example, it can be a conventional alkyl ester of titanate such as tetraethyl titanate or tetrabutyl titanate.

[0038] In this invention, the molar ratio of Nb / Ti in the niobium source and titanium source is 1~4:1; In this invention, the molar ratio of the auxiliary agent to the niobium source is 1~10:1, and more preferably 2~5:1; In this invention, the modified liquid may also contain acidic components; In this invention, the acidic component includes organic acids, and further includes at least one of oxalic acid, formic acid, acetic acid, propionic acid, butyric acid, lactic acid, tartaric acid, oxalic acid, malic acid, citric acid, etc.

[0039] In this invention, the weight ratio of the three-segment material to the niobium source is 1:0.02~0.2, and can be further 1:0.02~0.05.

[0040] In this invention, the solvent for solvothermal treatment is an aqueous solvent, preferably water, or a mixture of water and an organic solvent; the organic solvent is a water-soluble solvent.

[0041] In this invention, the solvothermal temperature is 150°C to 350°C, more preferably 160°C to 200°C.

[0042] In this invention, the solvothermal time is 5~20h.

[0043] The four sections of material were modified in an atmosphere containing a nitrogen source, and then the modified material was subjected to subsequent carbon coating treatment.

[0044] The nitrogen-containing atmosphere is ammonia, or a mixture of ammonia and a protective gas.

[0045] Preferably, the modification temperature is 550~800℃; the modification time is preferably 0.5~3h.

[0046] In this invention, the four-segment material and its modified material can be carbon-coated using conventional methods. For example, an optional approach of this invention involves mixing the four-segment material and a carbon source and heating them to perform the carbon-coating process.

[0047] In this invention, the carbon source is at least one of asphalt and resin.

[0048] In this invention, the amount of carbon source is 1~5 wt.%. The amount refers to the percentage of the carbon source relative to the weight of the unmodified graphite material (such as four-segment graphite or its modified form).

[0049] In this invention, the carbon coating stage includes a pre-carbonization process at a temperature of 450~650℃ and a carbonization process at a temperature of 600~1400℃. The pre-carbonization time can be 1~5 hours. The carbonization time can be 2~5 hours.

[0050] The present invention also provides a graphite-based regenerated active material for waste batteries prepared by the aforementioned method.

[0051] The preparation method described in this invention can endow the prepared material with special physicochemical properties, and the material with the aforementioned properties obtained by the preparation method can exhibit excellent low-temperature stability and fast-charging performance.

[0052] The present invention also provides an application of the graphite-based recycled active material of waste batteries prepared by the above preparation method, which is used as a negative electrode active material for the preparation of secondary batteries.

[0053] The present invention also provides a secondary battery comprising graphite-based recycled active material from waste batteries prepared by the aforementioned method.

[0054] In this invention, the recycled material described herein can be used as a negative electrode active material to prepare the required battery using conventional methods. For example, it can be combined with binders and conductive agents to prepare the negative electrode of a secondary battery. Furthermore, the negative electrode can be combined with a conventional positive electrode and a barrier layer (such as a separator or solid electrolyte) to form a cell of a secondary battery.

[0055] In this invention, the secondary battery, apart from containing the regenerated active material described in this invention, can have other conventional components and physicochemical structural features.

[0056] In this invention, the secondary battery can be a lithium-ion secondary battery or a sodium-ion secondary battery.

[0057] Beneficial effects This invention innovatively employs a multi-stage gas-liquid-gas-liquid combined processing approach, further enhanced by the coordinated control of the composition and conditions at each processing stage. This synergistic effect effectively and deeply removes harmful impurities, deeply repairs damaged physicochemical structures, and reconstructs ion and electron conduction networks. This facilitates the preparation of regenerable materials that combine excellent low-temperature stability with fast-charging performance. The results of the examples demonstrate that the material described in this invention exhibits excellent first-charge efficiency. Furthermore, at -40°C, the direct charge rate from 0% to 80% SOC is greater than 4C, and at -40°C, a full 4C charge does not result in lithium deposition, showcasing its excellent low-temperature fast-charging capability.

[0058] In this invention, based on the aforementioned multi-stage combined processing, the control of the halogen-containing atmosphere and the preferred modification of the nitrogen-containing source atmosphere help to further enhance the low-temperature fast-charging performance of recycled materials. Attached Figure Description

[0059] Figure 1 This is a SEM image of the regenerated graphite anode active material prepared in Example 1.

[0060] Figure 2 Image of the negative electrode interface of the soft-pack full cell prepared with the negative electrode of Example 1 after being fully charged at 4C at -40°C. Detailed Implementation

[0061] To better understand the present invention, the following description, in conjunction with embodiments, further illustrates the present invention; however, the implementation of the present invention is not limited thereto.

[0062] A method for preparing a low-temperature and fast-charging negative electrode for lithium-ion batteries using waste graphite, and a method for preparing the negative electrode material, comprising the following steps: A1 The waste graphite powder from lithium-ion batteries is placed in an atmosphere furnace and subjected to the first stage of gas phase treatment in an air atmosphere; a shaping and classifying machine is then used to shape and classify the material to obtain material with Dv50=6~8μm (first stage material). A2 A certain proportion of hydrochloric acid and oxidant are used as liquid phase treatment agents to perform a second stage of liquid phase treatment on the material obtained in step A1 (first stage material), followed by washing and drying to obtain the second stage material; A3 The material obtained from A2 was subjected to high-temperature heat treatment (third-stage gas phase treatment) in a graphitization furnace under a halogen-containing atmosphere to obtain a three-stage material. A4 Solution A is prepared by dissolving niobium pentachloride and oxalic acid in deionized water in a certain proportion; solution B is prepared by dissolving titanate and oxalic acid in anhydrous ethanol in a certain proportion; solution A is added dropwise to solution B to form solution C, and then a certain amount of ammonium fluoride is added to solution C and stirred until a transparent solution (modified solution) is obtained. The three-section material obtained in step A3 is added to the modified liquid in a certain proportion and stirred evenly to obtain a uniform slurry; then it is transferred to a Teflon-lined pressure cooker and subjected to hydrothermal treatment (fourth stage treatment) at a certain temperature; then it is washed with alcohol and dried to obtain the four-section material. A5 The material obtained in step A4 is placed in an atmosphere furnace, and ammonia or a mixture of ammonia and inert gas is introduced. It is then heat-treated at a certain temperature and then cooled to obtain the five-section material. A6 The material obtained in step A5 is mixed with the carbon source (binder) in a certain proportion in a VC high-speed mixer, then placed in a reaction vessel for granulation, cooling, and discharge; then placed in an atmosphere furnace for high-temperature carbonization under the protection of inert gas, cooled and discharged to obtain a low-temperature and fast-charging negative electrode material with Dv50=9.5~13.5μm.

[0063] The waste graphite mentioned in this invention can be a graphite-containing material obtained by stripping from waste batteries. For example, it can be obtained by stripping from the negative electrode of a lithium-ion battery using a conventional current collector. The graphite content can be reasonably adjusted according to the batch. For example, in the following cases, as an example, the graphite content in the waste graphite material can be 95±1wt.

[0064] In this invention, the hydrochloric acid and perchloric acid mentioned below refer to commercially available hydrochloric acid solutions and perchloric acid solutions.

[0065] Example 1 Step 1: The waste graphite powder from lithium-ion batteries was placed in an atmosphere furnace and kept at 400±20℃ for 3 hours in an air atmosphere for low-temperature heat treatment; then it was shaped and classified using a shaping and classifying machine to obtain material with Dv50=7μm (first-stage material). Step 2: 40wt% hydrochloric acid and 50wt% perchloric acid were mixed at a mass ratio of 2:3 to prepare a treatment solution. Then, the first stage material was placed in a reactor for treatment (the mass ratio of the first stage material to the treatment solution was 1:3, the treatment temperature was 80℃, and the treatment time was 10h). The solution was then washed with water until the pH of the filtrate was 6.5~7, and then dried to obtain the second stage material. Step 3 The Acheson graphitization furnace was used to process the second-stage material into a third-stage process. The steps were as follows: First, the system was heated to 2000℃. When the temperature was reached, a mixture of chlorine and dichlorofluoromethane (chlorine-containing atmosphere) was introduced, with a volume ratio of chlorine to dichlorofluoromethane of 1:1 and a flow rate of 0.3 kg / h per ton. The temperature was then increased to 2900℃ (processing temperature) and held at this temperature for 10 hours for the third-stage processing. Subsequently, the temperature was cooled to room temperature to obtain the three-stage material. The chlorine-containing atmosphere was stopped after the temperature dropped below 2000℃. Step 4 Solution A is prepared by dissolving niobium pentachloride and oxalic acid in deionized water at a molar ratio of 1:6; solution B is prepared by dissolving tetrabutyl titanate and oxalic acid in anhydrous ethanol at a molar ratio of 1:4; solution C is prepared by adding solution A dropwise to solution B (Nb / Ti molar ratio is 2:1); then a certain amount of ammonium fluoride is added to solution C at a molar ratio of niobium pentachloride and auxiliary agent (ammonium fluoride) of 1:4, and the mixture is stirred until a clear solution (modified solution) is obtained. The three-segment material was added to the modification liquid at a mass ratio of graphite:niobium pentachloride = 1:0.05 and stirred evenly to obtain a uniform slurry; then it was transferred to a Teflon-lined pressure cooker and subjected to liquid phase treatment at 180℃ for 12 hours; then it was washed with alcohol and dried to obtain the four-segment material. Step 5 The four-section material was placed in an atmosphere furnace, and the system was heated to 750°C under an ammonia atmosphere and held for 1.5 hours. Then it was cooled to obtain the five-section material. Step 6 The five-stage material and asphalt were mixed evenly in a VC high-speed mixer at a mass ratio of 1:0.03. Then, the mixture was placed in a reaction vessel and heated to 600℃ at a rate of 5℃ / min under the protection of inert gas (nitrogen) and held for 3 hours. After cooling, the mixture was discharged. Then, under the protection of inert gas, the mixture was heated to 1150℃ at a rate of 5℃ / min and held for 3 hours. After cooling, the mixture was discharged. The low-temperature and fast-charging negative electrode material (regenerated graphite active material) was obtained.

[0066] Example 2 Step 1: Waste graphite powder from lithium-ion batteries was placed in an atmosphere furnace and kept at 350±20℃ for 4 hours in an air atmosphere for low-temperature heat treatment; then it was shaped and classified using a shaping and grading machine to obtain material with Dv50=7μm (first-stage material). Step 2: 40wt% hydrochloric acid and 50wt% perchloric acid were mixed at a mass ratio of 1:1 to prepare a treatment solution. Then, the first stage material was placed in a reactor for treatment (the mass ratio of the first stage material to the treatment solution was 1:4, the treatment temperature was 70℃, and the treatment time was 15h). The solution was then washed with water until the pH of the filtrate was 6.5~7, and then dried to obtain the second stage material. Step 3 The Acheson graphitization furnace was used to process the second-stage material into a third-stage process. The steps were as follows: First, the system was heated to 2000℃. When the temperature was reached, a mixture of chlorine and dichlorofluoromethane (chlorine-containing atmosphere) was introduced, with a volume ratio of chlorine to dichlorofluoromethane of 1.5:1 and a flow rate of 0.2 kg / h per ton. The temperature was then increased to 2800℃ and held at this temperature for 12 hours for the third-stage process. Subsequently, the temperature was cooled to room temperature to obtain the three-stage material. The chlorine-containing atmosphere was stopped after the temperature dropped below 2000℃. Step 4 Solution A is prepared by dissolving niobium pentachloride and oxalic acid in deionized water at a molar ratio of 1:5; solution B is prepared by dissolving tetrabutyl titanate and oxalic acid in anhydrous ethanol at a molar ratio of 1:5; solution C is prepared by adding solution A dropwise to solution B (Nb / Ti molar ratio is 1:1); then a certain amount of ammonium chloride is added to solution C at a molar ratio of niobium pentachloride and ammonium chloride of 1:5, and the mixture is stirred until a clear solution (modified solution) is obtained. The three-segment material was added to the modification liquid at a mass ratio of graphite:niobium pentachloride = 1:0.04 and stirred evenly to obtain a uniform slurry; then it was transferred to a Teflon-lined pressure cooker and subjected to liquid phase treatment at 170℃ for 10 hours; then it was washed with alcohol and dried to obtain the four-segment material. Step 5 The four-section material was placed in an atmosphere furnace, and the system was heated to 700℃ under a 50% ammonia-Ar atmosphere and held for 2 hours. Then it was cooled to obtain the five-section material. Step 6 The five-stage material and asphalt were mixed evenly in a VC high-speed mixer at a mass ratio of 1:0.02. Then, the mixture was placed in a reaction vessel and heated to 500°C at a rate of 5°C / min under the protection of inert gas (nitrogen) and held for 4 hours. After cooling, the material was discharged. Then, the mixture was heated to 1000°C at a rate of 5°C / min under the protection of inert gas and held for 4 hours. After cooling, the material was discharged. The result was a low-temperature and fast-charging negative electrode material (regenerated graphite active material).

[0067] Example 3 Step 1: Waste graphite powder from lithium-ion batteries was placed in an atmosphere furnace and kept at 450±20℃ for 2 hours in an air atmosphere for low-temperature heat treatment; then it was shaped and classified using a shaping and classifying machine to obtain material with Dv50=6μm (first-stage material). Step 2: 40wt% hydrochloric acid and 50wt% perchloric acid were mixed at a mass ratio of 1:2 to prepare a treatment solution. Then, the first stage material was placed in a reactor for treatment (the mass ratio of the first stage material to the treatment solution was 1:3, the treatment temperature was 90℃, and the treatment time was 10h). The solution was then washed with water until the pH of the filtrate was 6.5~7, and then dried to obtain the second stage material. Step 3 The Acheson graphitization furnace was used to process the second-stage material into a third-stage process. The steps were as follows: First, the system was heated to 2000℃. When the temperature was reached, a mixture of chlorine and dichlorofluoromethane (chlorine-containing atmosphere) was introduced, with a volume ratio of chlorine to dichlorofluoromethane of 0.5:1 and a feeding rate of 0.4 kg / h per ton. The temperature was then increased to 3000℃ and held at this temperature for 8 hours for the third-stage process. Subsequently, the temperature was cooled to room temperature to obtain the three-stage material. The chlorine-containing atmosphere was stopped after the temperature dropped below 2000℃. Step 4 Solution A is prepared by dissolving niobium pentachloride and oxalic acid in deionized water at a molar ratio of 1:4; solution B is prepared by dissolving tetrabutyl titanate and oxalic acid in anhydrous ethanol at a molar ratio of 1:3; solution C is prepared by adding solution A dropwise to solution B (Nb / Ti molar ratio is 3:1); then a certain amount of cyanamide is added to solution C at a molar ratio of niobium pentachloride and cyanamide of 1:2, and the mixture is stirred until a clear solution (modified solution) is obtained. The three-segment material was added to the modification liquid at a mass ratio of graphite:niobium pentachloride = 1:0.02 and stirred evenly to obtain a uniform slurry; then it was transferred to a Teflon-lined pressure cooker and subjected to liquid phase treatment at 200℃ for 8 hours; then it was washed with alcohol and dried to obtain the four-segment material. Step 5 The four-section material was placed in an atmosphere furnace, and the system was heated to 750°C under an ammonia atmosphere and held for 1 hour. Then it was cooled to obtain the five-section material. Step 6 The five-stage material and asphalt were mixed evenly in a VC high-speed mixer at a mass ratio of 1:0.04. Then, the mixture was placed in a reaction vessel and heated to 650°C at a rate of 5°C / min under the protection of inert gas (nitrogen) and held for 2 hours. After cooling, the mixture was discharged. Then, under the protection of inert gas, the mixture was heated to 1100°C at a rate of 5°C / min and held for 3 hours. After cooling, the mixture was discharged. The low-temperature and fast-charging negative electrode material (regenerated graphite active material) was obtained.

[0068] Example 4 Compared with Example 1, the only difference is that in step 3, the chlorine-containing atmosphere is changed, specifically: Group A: The chlorine-containing atmosphere is replaced with chlorine gas; Group B: The chlorine-containing atmosphere is replaced with dichlorofluoromethane; The total amount of chlorine-containing gas used and other operations and parameters are the same as in Example 1.

[0069] Example 5 Compared with Example 1, the only difference is that step 5 is omitted, and the product of step 4 is directly used as raw material for the processing of step 6. All other operations and parameters are the same as in Example 1.

[0070] Comparative Example 1 Compared with Example 1, the only difference is that the air in step 1 is replaced with nitrogen, while the other operations and parameters are the same as in Example 1.

[0071] Comparative Example 2 Compared with Example 1, the only difference is that in step 2, no oxidant (perchloric acid) is added; all other operations and parameters are the same as in Example 1.

[0072] Comparative Example 3 Compared with Example 1, the only difference is that in step 3, a chlorine-containing atmosphere is not introduced (Ar is used instead of the chlorine-containing atmosphere), and all other operations and parameters are the same as in Example 1.

[0073] Comparative Example 4 Compared with Example 1, the only difference is that in step 3, the system is heated to 1800°C, then the chlorine-containing atmosphere is introduced, and the third stage of treatment is carried out at this temperature. All other operations and parameters are the same as in Example 1.

[0074] Comparative Example 5 Compared with Example 1, the only difference is that step 4 is a solid-phase treatment process. That is, the solid components in the three-stage material and the modified liquid are mixed and kept at 800°C for 2 hours to obtain the four-stage material, and then the subsequent treatment is carried out. All other operations and parameters are the same as in Example 1.

[0075] Comparative Example 6 Compared with Example 1, the only difference is that ammonium fluoride is missing in step 4, while the other operations and parameters are the same as in Example 1.

[0076] The microstructure of the sample was tested using a scanning electron microscope.

[0077] Electrodes were fabricated using the materials described in the embodiments and comparative examples, with lithium metal sheets used as the counter electrode to construct half-cells. The electrode slurry formulation consisted of the negative electrode active material (recycled material in each case): PVDF:SP = 91.6:6.6:1.8. The initial charge-discharge curves and initial coulombic efficiency of the half-cells were tested using a Landian testing system manufactured by Wuhan Landian Electronics Co., Ltd.

[0078] Using the materials described in each embodiment and comparative example as the anode active material, low-temperature LFP (lithium iron phosphate) as the cathode active material, and low-temperature electrolyte, soft-pack stacked three-electrode full cells were fabricated, with a total capacity of approximately 700mAh. The positive electrode slurry formulation was LFP:PVDF:SP = 96.0:2.0:2.0, and the negative electrode formulation was the negative electrode active material (recycled material in each case): SP:CMC:SBR = 95.3:1.0:1.2:2.5, with a full cell NP ratio of 1.15. The charging performance of the full cell was tested using the Landian testing system manufactured by Wuhan Landian Electronics Co., Ltd. The cells were charged from 0% SOC to 80% maximum charge rate at -40℃. After 10 cycles of 4C charging and 1C discharging at -40℃, the cells were fully charged at 4C, and then the negative electrode interface was observed after disassembly. The low-temperature and fast-charging negative electrode products of Examples 1-5 and Comparative Examples 1-6 were tested respectively, and the test results are shown in Table 1.

[0079]

[0080] The above embodiments only illustrate several implementation methods of the present invention. The descriptions are relatively specific and detailed, but they should not be construed as allowing for various modifications and improvements to be made based on the concept of the present invention. These modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the claims used.

Claims

1. A method for preparing graphite-based recycled active materials from waste batteries, characterized in that, The waste graphite material stripped from waste batteries is pre-treated in an oxidizing atmosphere to obtain a first-stage gas phase treatment. The first stage material is placed in an acidic treatment solution with oxidizing properties for a second stage of liquid phase treatment to obtain the second stage material; The second-stage material is placed in a halogen-containing atmosphere and subjected to a third-stage gas phase treatment at a temperature above 2000℃ to obtain the third-stage material. The three-stage material is placed in a modified liquid containing niobium source, titanium source and additives for a fourth stage of solvothermal treatment to obtain a four-stage material; the additives are at least one of ammonium fluoride, ammonium chloride, cyanamide and urea; The graphite-based recycled active material from waste batteries is obtained by coating the four sections of material with carbon.

2. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, The waste batteries mentioned include at least one of waste lithium-ion batteries and waste sodium-ion batteries; Preferably, the graphite content in the waste graphite material is above 80 wt.%.

3. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, The oxidizing atmosphere is an atmosphere containing oxygen; Preferably, the temperature of the first stage of gas phase treatment is 300~500℃; Preferably, the duration of the first stage of gas phase treatment is 1-5 hours; Preferably, after the first stage of gas phase treatment, a shaping and grading process can be performed to obtain a first-stage material; Preferably, the D50 of the first section of material is controlled to be 6~8μm.

4. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, The acidic treatment solution is a mixed solution containing acid and oxidant; Preferably, the acid is an inorganic strong acid, and more preferably at least one of hydrochloric acid and sulfuric acid; Preferably, the oxidant is at least one selected from hypochlorite, FeCl3, SnCl4, perchloric acid, perchlorate, oxygen, oxygen-enriched air, and ozone. Preferably, in the acidic treatment solution, the concentration of the acid is 1-20 wt%; the concentration of the oxidant is 2-30 wt%; the concentration of the acid is 5-20 wt%; and the concentration of the oxidant is 10-25 wt%. Preferably, the temperature of the second liquid phase treatment stage is 30~100℃, and more preferably 60~90℃; Preferably, the second stage of liquid phase treatment takes 5 to 20 hours, and more preferably 8 to 15 hours; Preferably, after the second stage of liquid phase treatment, the material undergoes solid-liquid separation, water washing, and drying to obtain the second-stage material.

5. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, In the halogen-containing atmosphere, the halogen is at least one of elemental halogens and halogenated hydrocarbon gases; preferably chlorine. Preferably, the temperature of the third stage of gas phase treatment is 2000~3300℃; more preferably, it is 2850~3300℃. Preferably, the time for the third stage of gas phase treatment is 5~72 hours; Preferably, the halogen-containing atmosphere is at least one of chlorine gas and haloalkane gas, and more preferably a mixture of chlorine gas and haloalkane gas.

6. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, In the modified liquid, the niobium source is at least one of niobium pentachloride, niobium trichloride, niobium fluoride, niobium bromide, and niobium iodide; Preferably, the titanium source is a titanate ester; Preferably, the molar ratio of Nb / Ti in the niobium source and titanium source is 1~4:1; Preferably, the molar ratio of the auxiliary agent to the niobium source is 1~10:1; Preferably, the modified liquid may also contain acidic components; Preferably, the acidic component includes organic acids, and further includes at least one of oxalic acid, formic acid, acetic acid, propionic acid, butyric acid, lactic acid, tartaric acid, oxalic acid, malic acid, citric acid, etc. Preferably, the weight ratio of the three-section material to the niobium source is 1:0.02~0.2; Preferably, the solvent for solvothermal treatment is an aqueous solvent, preferably water, or a mixture of water and an organic solvent; the organic solvent is a water-soluble solvent. Preferably, the solvothermal temperature is 150°C to 350°C, more preferably 160°C to 200°C; Preferably, the solvothermal time is 5 to 20 hours.

7. The method for preparing graphite-based recycled active materials from waste batteries as described in claim 1, characterized in that, The four sections of material were modified in an atmosphere containing a nitrogen source, and then the modified material was subjected to subsequent carbon coating treatment. Preferably, the nitrogen source is ammonia or a mixture of ammonia and an inert gas; Preferably, the modification temperature is 550~850℃, more preferably 700~800℃; Preferably, the carbon source selected for carbon coating is at least one of asphalt and resin; Preferably, the amount of carbon source is 1~5 wt.%; Preferably, the carbon coating stage includes a pre-carbonization process at a temperature of 400~650℃ and a carbonization process at a temperature of 600~1400℃; more preferably, the pre-carbonization process temperature is 550~650℃ and the carbonization process temperature is 1000~1200℃.

8. A graphite-based recycled active material from waste batteries prepared by the method described in any one of claims 1 to 7.

9. The application of a graphite-based recycled active material from waste batteries prepared by the method according to any one of claims 1 to 7, characterized in that, It is used as a negative electrode active material in the preparation of secondary batteries.

10. A secondary battery, characterized in that, The invention comprises graphite-based recycled active material from waste batteries prepared by the preparation method according to any one of claims 1 to 7.

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