Regeneration and restoration method of graphite waste residue after wet lithium extraction of waste lithium battery

Abstract

The invention discloses a regeneration and restoration method of graphite waste residues after wet lithium extraction of waste lithium batteries, and relates to the technical field of solid waste recovery. The invention provides a combined treatment technical means of adding inorganic strong alkali or carbonate for mixing, performing heat treatment, performing high-pressure acid leaching, preparing slurry and performing spiral separation, so that the content of ash impurities in the lithium extraction graphite is greatly reduced, particularly, ZrO2, TiO2 and other impurities can be effectively removed, and high-purity graphite is obtained. The obtained high-purity graphite is mixed with a coating agent and then carbonized, so that the microstructure and the specific surface area of the graphite material are optimized, and finally the lithium battery negative electrode graphite material with high purity, high capacity and high first efficiency is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste recycling, and in particular to a method for regenerating and repairing graphite waste residues after wet lithium extraction from waste lithium batteries. Background Art

[0002] The development of new energy electric vehicles (EVs) and the electronics industry will generate a large amount of waste lithium-ion batteries, and their effective recycling can avoid environmental pollution and save precious resources. At present, research on the recycling of waste lithium-ion batteries mainly focuses on pyrometallurgy and hydrometallurgy, while there is little research on the recycling of completed parts and components, especially for the recycling of graphite after hydrometallurgical lithium extraction from waste lithium batteries. There is no effective and cost-effective method. With the accumulation of waste lithium-ion batteries and the shortage of energy, the recycling of graphite has also received increasing attention. However, despite the reports of various methods, the recycled graphite cannot meet the strict commercial standards of purity, efficiency and capacity.

[0003] The graphite slag after recycling high-value metals by acid leaching, extraction and other lithium extraction methods not only contains a small amount of positive materials, a small amount of electrolyte, heavy metals and other impurities, but also contains a small amount of ZrO 2 、TiO 2 and Al 2 O 3 etc., leading to acid leaching and extraction (ZrO 2 、TiO 2 Due to its strong chemical stability, these oxides still remain in the graphite waste, which brings great difficulties to the purification and repair of graphite waste. In addition, graphite waste contains a part of conductive carbon black and binders such as SBR, PVDF, and CMC. If mixed with graphite, it will not only affect the capacity of graphite, but also reduce the BET of graphite, thereby increasing the irreversible capacity of graphite and reducing the first coulomb efficiency.

[0004] Therefore, there is an urgent need to provide a short-process, easy-to-operate method to treat the graphite waste slag after lithium extraction, so as to obtain high-performance negative electrode graphite materials with both purity, capacity and initial efficiency.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, aiming to provide a short-process, easy-to-operate method for treating the graphite waste residue after lithium extraction to obtain high-purity graphite.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, comprising:

[0009] Mixing the graphite waste with an inorganic strong base or a carbonate, and then performing a heat treatment to obtain a first graphite material;

[0010] The first graphite material is mixed with a treatment liquid containing an inorganic acid and an oxidant, and high-pressure acid leaching is performed to obtain a second graphite material after solid-liquid separation;

[0011] Mixing the second graphite material and water to prepare a slurry to obtain a graphite slurry;

[0012] The graphite slurry is passed into a spiral centrifuge for centrifugal separation to obtain a third graphite material.

[0013] In an optional embodiment, during the preparation of the first graphite material, the heat treatment temperature is 800° C.-1200° C., and the holding time is 2 h-10 h;

[0014] and / or, heat treatment is performed under an inert atmosphere.

[0015] In an optional embodiment, the inorganic strong base is selected from at least one of sodium hydroxide and potassium hydroxide, and the mass ratio of the graphite waste slag to the inorganic strong base is 100:(3-10);

[0016] and / or, the carbonate is selected from at least one of sodium carbonate and potassium carbonate, and the mass ratio of the graphite waste slag to the carbonate is 100:(3-10);

[0017] And / or, the graphite waste slag is first dried and then mixed with the inorganic strong base or carbonate, and the drying temperature is controlled to be 80° C.-200° C. and the drying time is 10 h-30 h.

[0018] In an optional embodiment, during the preparation of the second graphite material, the reaction temperature of the high-pressure acid leaching is 110° C.-180° C., the reaction pressure is 1 MPa-2 MPa, the reaction time is 60 min-36 h, and then the temperature is reduced and the pressure is released before solid-liquid separation;

[0019] And / or, the inorganic acid in the treatment liquid is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid.

[0020] In an optional embodiment, the inorganic acid in the treatment solution is a mixed acid, and the mixed acid includes sulfuric acid;

[0021] and / or, the oxidant in the treatment liquid is hydrogen peroxide;

[0022] And / or, the concentration of the inorganic acid in the treatment liquid is 1 mol / L-5 mol / L, and the concentration of the oxidant is 0.1 mol / L-0.5 mol / L.

[0023] In an optional embodiment, the solid content of the graphite slurry is 10%-30%;

[0024] And / or, the preparation process of the graphite slurry includes: mixing the second graphite material and water, and dispersing the particles in the slurry at a rotation speed of 600 rpm-1000 rpm for 30 min-60 min.

[0025] In an optional embodiment, in the process of separating the third graphite material from the graphite slurry, the stirring speed of the spiral centrifuge is controlled to be 300rpm-600rpm, the centrifugal speed is controlled to be 2500rpm-4500rpm, and the separated and purified graphite material is collected after centrifugation.

[0026] In an optional embodiment, the method further includes: mixing a third graphite material with a coating agent to obtain a mixed material, and carbonizing the mixed material;

[0027] Wherein, the coating agent is selected from at least one of asphalt and phenolic resin.

[0028] In an optional embodiment, the third graphite material is dried and then mixed with the coating agent, and the mass ratio of the graphite material to the coating agent is controlled to be 100:(2-10);

[0029] and / or, during the mixing process with the coating agent, the stirring speed is controlled to be 1000 rpm-2000 rpm, and the mixing time is 10 min-30 min;

[0030] And / or, the coating agent is asphalt, the particle size D50 of the asphalt is 2 μm-6 μm, and the softening point of the asphalt is 230° C.-260° C.;

[0031] And / or, the drying temperature of the third graphite material is 80° C.-200° C., and the drying time is 10 h-30 h.

[0032] In an optional embodiment, during the carbonization treatment of the mixed material, the carbonization temperature is controlled to be 900° C.-1400° C., and the insulation time is 1 h-5 h;

[0033] And / or, the temperature is raised to the carbonization temperature at a heating rate of 2°C / min-5°C / min.

[0034] The present invention has the following beneficial effects: The present invention proposes a combined treatment technology of adding inorganic strong alkali or carbonate mixing-heat treatment-high pressure acid leaching-slurry preparation-spiral separation, which greatly reduces the ash impurity content in lithium-extracted graphite, and can effectively remove ZrO 2 、TiO 2 Impurities such as quartz and niobium can be removed to obtain high-purity graphite.

[0035] In a preferred embodiment, the obtained high-purity graphite is mixed with a coating agent and then carbonized to optimize the microstructure and specific surface area of ​​the graphite material, thereby ultimately obtaining a high-purity, high-capacity, and high-initial-efficiency lithium battery negative electrode graphite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 Schematic diagram of spiral centrifugal separation of graphite and carbon black and amorphous carbon produced by pyrolysis and carbonization;

[0038] Figure 2 This is the SEM image of the recycled graphite. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0040] In view of the problem that doping elements are difficult to remove in the existing process of recycling graphite waste, the embodiment of the present invention proposes a short process, convenient and fast technical means to treat the graphite waste after lithium extraction, so as to achieve the purpose of deep impurity removal and obtain high-purity graphite that meets commercial requirements. Further, a coating method is used to repair the defects in the graphite and the graphite structure, and finally a high-performance negative electrode graphite material with both purity, capacity and first effect is prepared, which solves the problem of difficult graphite waste recycling in this industry and enables industrial hazardous waste to be utilized as a resource.

[0041] The embodiment of the present invention provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0042] S1. Heat treatment with inorganic strong alkali or carbonate

[0043] The graphite waste is mixed with an inorganic strong base or a carbonate, and then heat-treated to convert impurities into salts that are easily removed by acid leaching, thereby obtaining a first graphite material.

[0044] Specifically, by mixing graphite waste slag with inorganic strong alkali or carbonate for heat treatment, ZrO 2、TiO 2 It is converted into zirconate and titanate, which are easily soluble in acid, making it convenient to remove Zr and Ti impurities by acid leaching. At the same time, the PVDF in the binder will undergo and accelerate the dehydrofluorination reaction under the action of alkali or carbonate, and undergo cracking and carbonization.

[0045] In some embodiments, the inorganic strong base is selected from at least one of sodium hydroxide and potassium hydroxide, and the inorganic strong base can be any one or more of the above, and the mass ratio of the graphite waste slag to the inorganic strong base is 100: (3-10), such as 100: 3, 100: 4, 100: 5, 100: 6, 100: 7, 100: 8, 100: 9, 100: 10, etc. The carbonate is selected from at least one of sodium carbonate and potassium carbonate, and the carbonate can be any one or more of the above, and the mass ratio of the graphite waste slag to the carbonate is 100: (3-10), such as 100: 3, 100: 4, 100: 5, 100: 6, 100: 7, 100: 8, 100: 9, 100: 10, etc. The amount of the inorganic strong base or carbonate is controlled within the above range, which can make the ZrO in the graphite waste slag 2 、TiO 2 etc. are fully converted into salts that are easily soluble in acid, thereby improving the impurity removal effect.

[0046] In some embodiments, during the preparation of the first graphite material, the heat treatment temperature is 800°C-1200°C, such as 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.; the heat preservation time is 2h-10h, such as 2h, 3h, 5h, 8h, 10h, etc. The heat treatment temperature and time are preferably within the above ranges to reduce the ZrO in the graphite waste slag. 2 、TiO 2 The heat treatment process can be carried out under an inert atmosphere. The type of inert atmosphere is not limited, such as nitrogen, argon, etc.

[0047] In some embodiments, the graphite waste is dried before mixing with the inorganic strong base or carbonate to avoid the influence of water and other impurities on the surface of the graphite waste on the heat treatment. The drying temperature is 80°C-200°C, such as 80°C, 100°C, 130°C, 150°C, 180°C, 200°C, etc.; the drying time is 10h-30h, such as 10h, 15h, 20h, 25h, 30h, etc.

[0048] S2, high pressure acid leaching

[0049] The first graphite material is mixed with a treatment solution containing an inorganic acid and an oxidant, and high-pressure acid leaching is performed to remove impurity elements into the acid leaching solution through acid leaching, and the second graphite material is obtained after solid-liquid separation.

[0050] It should be noted that the high-pressure acid leaching provided in the embodiment of the present invention has two effects: (1) high-pressure acid leaching increases the reaction kinetics of the acid leaching reaction, promotes the acid leaching efficiency and increases the impurity removal rate. By the above-mentioned alkali or carbonate heat treatment + high-pressure acid leaching combined treatment, graphite with an ash content of less than 0.1% is obtained. By optimizing the acid leaching conditions, high-purity graphite with an ash content of less than 0.05% can be obtained; (2) in high-pressure acid leaching, the incompletely pyrolyzed residues of CMC (carboxymethyl cellulose), PVDF (polyvinylidene fluoride), and SBR (styrene-butadiene rubber) in the graphite will be hydrothermally carbonized under the action of high-pressure hydrothermal treatment and converted into fine amorphous carbon particles, preparing for the removal of conductive carbon black and amorphous carbon particles after hydrothermal carbonization in subsequent steps.

[0051] In some embodiments, during the preparation of the second graphite material, the reaction temperature of the high-pressure acid leaching is 110°C-180°C, the reaction pressure is 1MPa-2MPa, the reaction time is 60min-36h, and after heat preservation and pressure maintenance, the temperature is reduced and the pressure is released before solid-liquid separation. By regulating the temperature, pressure, time, etc. of the acid leaching, the removal effect of impurities is improved, thereby improving the purity of the graphite product. Specifically, the reaction temperature of the high-pressure acid leaching can be 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc.; the reaction pressure can be 1.0MPa, 1.3MPa, 1.5MPa, 1.8MPa, 2.0MPa, etc.; the reaction time can be 60min, 3h, 5h, 8h, 10h, 15h, 20h, 25h, 30h, 36h, etc.

[0052] In some embodiments, the inorganic acid in the treatment liquid is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid, and the inorganic acid can be any one or more of the above. Preferably, the inorganic acid in the treatment liquid is a mixed acid, and the mixed acid includes sulfuric acid, that is, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, or a mixed acid of sulfuric acid and nitric acid. The oxidant in the treatment liquid is hydrogen peroxide, but is not limited thereto, and the hydrogen peroxide raw material is easily available and does not introduce impurities.

[0053] Furthermore, the concentration of inorganic acid in the treatment liquid is 1mol / L-5mol / L, such as 1mol / L, 2mol / L, 3mol / L, 4mol / L, 5mol / L, etc.; the concentration of oxidant is 0.1mol / L-0.5mol / L, such as 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, etc.

[0054] S3, pulping, spiral separation

[0055] The second graphite material is mixed with water to obtain a graphite slurry; the graphite slurry is passed into a spiral centrifuge (such as a horizontal spiral centrifuge) for centrifugal separation to obtain a third graphite material. Figure 1 As shown, the graphite particles can be separated and the non-graphite carbon removed.

[0056] The solid content of the graphite slurry is 10%-30%, such as 10%, 15%, 20%, 25%, 30%, etc. The stirring speed of the spiral centrifuge is controlled to be 300rpm-600rpm, such as 300rpm, 400rpm, 500rpm, 600rpm, etc. The centrifugal speed is 2500rpm-4500rpm, such as 2500rpm, 3000rpm, 3500rpm, 4000rpm, 4500rpm, etc. The centrifugal time is not limited, and the feeding and discharging method is adopted. After the centrifugation is completed, the separated and purified graphite material is collected.

[0057] It should be noted that the present invention creatively proposes to centrifuge graphite slurry by spiral centrifuge, and effectively separates graphite and non-graphite carbon (amorphous carbon produced by pyrolysis and carbonization of conductive carbon black, CMC, PVDF, SBR) in graphite material by controlling the solid content and centrifugal speed of the prepared slurry. In addition, part of the micropowder in graphite will also be separated from graphite due to its small specific gravity, which plays a role in removing micropowder. By removing non-graphite carbon (amorphous carbon produced by pyrolysis and carbonization of conductive carbon black, CMC, PVDF, SBR) and graphite micropowder, the specific surface area and compacted density of the obtained graphite material can be improved. Since the presence of non-graphite carbon can reduce the capacity of graphite as a negative electrode material for lithium ion batteries, the final capacity of graphite can be effectively improved by removing non-graphite carbon and graphite micropowder.

[0058] Specifically, the horizontal spiral centrifuge is a commercially available device, such as the LW series model that can be purchased from Jiangsu Saideli Pharmaceutical Machinery Manufacturing Co., Ltd. The spiral centrifuge contains a mixer, a spiral separator, a spiral conveyor, and the like.

[0059] like Figure 1As shown, the graphite slurry is subjected to spiral separation treatment on a horizontal spiral centrifuge. Due to the density difference between the materials, water and graphite particles are deposited on the drum wall and form a precipitate. The screw conveyor rotates to the drum at a higher speed and conveys the graphite particles precipitated from the centrifuge. At the same time, a liquid level is formed on the drum wall, and its height is adjusted by the regulator to adjust the overflow weir. Most of the amorphous carbon produced by cracking and carbonizing binders such as conductive carbon black, CMC, PVDF, SBR, etc. flows with water and flows along the screw to the end of the cylindrical drum and the drain. Since the carbon black particles and the amorphous carbon produced by pyrolysis and carbonization have a very low content, they have a much lower sedimentation rate than graphite, because they have a small density difference with water, a small particle size, and a long residence time in water, and the centrifuge is not enough to deposit these particles on the drum wall. Therefore, the method provided in the embodiment of the present invention can effectively separate the graphite in the slurry from the conductive carbon black and the amorphous carbon produced by pyrolysis and carbonization of the binder.

[0060] In the actual operation process, a peristaltic pump is used to supply the graphite slurry in the container to the spiral centrifuge, and the agitator system is controlled to stir the slurry in the container at a speed of 300-600rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 2500-4500rpm. After centrifugation, the separated and purified graphite material is collected to obtain a third graphite material.

[0061] In some embodiments, the preparation process of the graphite slurry includes: mixing the second graphite material and water, dispersing the particles in the slurry at a speed of 600rpm-1000rpm for 30min-60min to make the particles evenly distributed. Specifically, the slurry can be prepared in a container of a three-blade propeller stirrer, and the stirring speed can be controlled to be 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc., and the stirring and dispersing time can be 30min, 40min, 50min, 60min, etc.

[0062] S4, surface coating

[0063] The third graphite material is mixed with a coating agent to obtain a mixture, and the mixture is carbonized. By coating the mixture with a coating agent such as asphalt, the microstructure and specific surface area of ​​the graphite material can be optimized, and the capacity and primary efficiency of the graphite can be improved.

[0064] In some embodiments, the coating agent is selected from at least one of asphalt and phenolic resin, and the coating agent can be any one or more of the above. Preferably, the coating agent is asphalt, the particle size D50 of the asphalt is 2μm-6μm, and the softening point of the asphalt is 230℃-260℃. The use of asphalt coating is conducive to further improving the capacity and initial effect of the product.

[0065] In some embodiments, the third graphite material is dried and then mixed with the coating agent, and the mass ratio of the graphite material to the coating agent is controlled to be 100: (2-10), such as 100: 2, 100: 3, 100: 4, 100: 5, 100: 6, 100: 7, 100: 8, 100: 9, 100: 10, etc. The amount of the coating agent is preferably within this range, which can effectively improve the capacity and first effect of the graphite product. The drying temperature of the third graphite material is 80°C-200°C (such as 80°C, 100°C, 150°C, 200°C, etc.), and the drying time is 10h-30h (such as 10h, 15h, 20h, 25h, 30h, etc.).

[0066] Furthermore, the mixing process with the coating agent can be carried out in a high-speed mixer, and the stirring speed is controlled to be 1000rpm-2000rpm, such as 1000rpm, 1500rpm, 2000rpm, etc.; the mixing time is 10min-30min, such as 10min, 20min, 30min, etc.

[0067] Furthermore, during the carbonization treatment of the mixture, the temperature is raised to a carbonization temperature of 900°C-1400°C at a heating rate of 2°C / min-5°C / min, and the holding time is controlled to be 1h-5h. Under this carbonization temperature and time condition, a more uniform coating can be achieved, and the comprehensive performance of the graphite product can be improved. Specifically, the heating rate can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, etc.; the carbonization temperature can be 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, etc.; the holding time can be 1h, 2h, 3h, 4h, 5h, etc. After carbonization treatment, it is sieved and demagnetized to finally obtain high-purity, high-capacity, high-first-effect lithium-ion battery negative electrode graphite.

[0068] It should be noted that the regeneration and repair method provided in the embodiment of the present invention can effectively recycle graphite, and ultimately obtain lithium battery negative electrode graphite material with high purity (ash content <0.1%, or even <0.05%), high capacity (capacity >350mAh / g), and high initial efficiency (initial efficiency >93%).

[0069] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0070] It should be noted that the preparation process of the graphite waste slag treated in the following examples and comparative examples is as follows: The waste lithium-ion batteries (ternary batteries recycled from battery sources) are subjected to the following operations: 1. Pretreatment of waste lithium batteries: The waste batteries are crushed and sorted, and the outer packaging, electrolytes and electrode materials are removed to obtain battery black powder. 2. The battery black powder is placed in an acidic solution for acid leaching. Sulfuric acid or hydrochloric acid is usually used to dissolve the electrode materials and electrolytes and convert them into water-soluble salts; 3. Solution separation, after acid leaching, the solid waste slag is separated by filtration or centrifugation (the water-soluble salt solution is used for subsequent precipitation, lithium extraction, impurity removal and other operations), and the solid waste slag obtained is graphite waste slag. The impurity composition of the waste slag is shown in Table 1.

[0071] Example 1

[0072] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0073] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH (i.e., the mass ratio of sodium hydroxide to graphite waste slag (the same below) is 5:100) to the dried graphite waste slag and mixing them evenly in a high-speed mixer, wherein the mixing speed used during mixing is 1500 rpm and the mixing time is 15 min.

[0074] (2) The above-mentioned graphite waste slag mixed with NaOH was heat-treated in an inert atmosphere (nitrogen, the same below) at a heat treatment temperature of 950° C. and a holding time of 6 hours to obtain a first graphite material.

[0075] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2.0 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0076] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0077] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0078] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0079] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0080] The morphology of the regenerated graphite product prepared in Example 1 is as follows Figure 2 As shown, it can be seen that the graphite is in blocky particles with a particle size of less than 50 μm. The graphite particles are uniform and have a smooth surface.

[0081] Example 2

[0082] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0083] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0084] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h to obtain a first graphite material.

[0085] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 160°C, the reaction pressure is 1.0-1.5 MPa, the reaction time is 4 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0086] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0087] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0088] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0089] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0090] Example 3

[0091] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0092] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0093] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h to obtain a first graphite material.

[0094] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2.0 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0095] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0096] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the third graphite material after separation and purification is collected.

[0097] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0098] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1100°C, and the carbonization insulation time is 4 hours. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0099] Example 4

[0100] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0101] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 8% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0102] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h to obtain a first graphite material.

[0103] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0104] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0105] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0106] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0107] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0108] Example 5

[0109] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0110] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 8% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0111] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h to obtain a first graphite material.

[0112] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 160°C, the reaction pressure is 1.0-1.5 MPa, the reaction time is 4 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0113] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0114] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0115] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0116] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0117] Example 6

[0118] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0119] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% KOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0120] (2) The graphite waste slag mixed with KOH is heat-treated under an inert atmosphere at a temperature of 950° C. and a holding time of 6 h to obtain a first graphite material.

[0121] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2.0 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0122] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0123] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0124] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0125] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0126] Example 7

[0127] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0128] (1) drying the graphite waste at 120° C. for 12 h to obtain dried graphite waste; adding 5% Na 2 CO 3 Mix evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 minutes.

[0129] (2) Mix the above-mentioned 2CO 3 The graphite waste slag is heat treated in an inert atmosphere at a temperature of 900° C. and a holding time of 8 hours to obtain a first graphite material.

[0130] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0131] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0132] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0133] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0134] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0135] Example 8

[0136] This embodiment provides a method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, and the steps are as follows:

[0137] (1) drying the graphite waste at 120° C. for 12 h to obtain dried graphite waste; adding 5% K 2 CO 3Mix evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 minutes.

[0138] (2) Mix the above 2 CO 3 The graphite waste slag is heat treated in an inert atmosphere at a temperature of 900° C. and a holding time of 8 hours to obtain a first graphite material.

[0139] (3) Pour the first graphite material into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, wherein the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and the solid-liquid separation is performed to obtain the second graphite material.

[0140] (4) The second graphite material is slurried in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0141] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After the centrifugation is completed, the third graphite material after separation and purification is collected.

[0142] (6) The third graphite material is dried at 120° C. for 12 h to obtain dried high-purity graphite, and the high-purity graphite and asphalt are mixed uniformly in a high-speed mixer at a mass ratio of 100:3. The particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250° C., the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0143] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain high-purity, high-capacity, and high-initial-efficiency lithium-ion battery negative electrode graphite.

[0144] Example 9

[0145] The only difference from Example 1 is that 3% sodium hydroxide is added in step (1).

[0146] Example 10

[0147] The only difference from Example 1 is that 8% sodium hydroxide is added in step (1).

[0148] Embodiment 11

[0149] The only difference from Example 1 is that the heat treatment temperature in step (2) is 1150°C and the holding time is 3.5h.

[0150] Example 12

[0151] The only difference from Example 1 is that the heat treatment temperature in step (2) is 1100°C and the holding time is 4h.

[0152] Embodiment 13

[0153] The only difference from Example 1 is that the solid ratio of the acid leaching solution in step (3) is 8 mL / g

[0154] Comparative Example 1

[0155] The difference between Comparative Example 1 and Example 1 is that no inorganic strong base or carbonate is added in step (1), and the steps are as follows:

[0156] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag.

[0157] (2) The dried graphite waste slag is heat treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h.

[0158] (3) Pour the graphite waste residue after the above heat treatment into a treatment liquid containing inorganic acid and hydrogen peroxide, the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. High-pressure acid leaching treatment is carried out in the treatment liquid, the liquid-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and solid-liquid separation is performed to obtain graphite material A.

[0159] (4) The graphite obtained by the solid-liquid separation is prepared into a slurry in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0160] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0161] (6) Graphite material B is dried at 120°C for 12 h to obtain dried high-purity graphite, and the high-purity graphite and a certain proportion of asphalt (the proportion is the same as in Example 1) are mixed evenly in a high-speed mixer, the particle size of the asphalt is D50 = 2 to 3 μm, the softening point of the asphalt is about 250°C, the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0162] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain a graphite product.

[0163] Comparative Example 2

[0164] The difference between Comparative Example 2 and Example 1 is that the heat treatment in step (2) is not performed, and high pressure acid leaching is performed directly, and the steps are as follows:

[0165] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0166] (2) Pour the above-mentioned graphite waste residue mixed with NaOH into a treatment liquid containing inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform high-pressure acid leaching in the treatment liquid, the liquid-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and solid-liquid separation is performed to obtain graphite material A.

[0167] (3) The graphite obtained by the solid-liquid separation is prepared into a slurry in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0168] (4) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0169] (5) Graphite material B is dried at 120°C for 12 h to obtain dried high-purity graphite, and the high-purity graphite and a certain proportion of asphalt (the proportion is the same as in Example 1) are mixed evenly in a high-speed mixer, the particle size of the asphalt is D50 = 2 to 3 μm, the softening point of the asphalt is about 250°C, the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0170] (6) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain a graphite product.

[0171] Comparative Example 3

[0172] The difference between Comparative Example 3 and Example 1 is mainly that step (4) and step (5) in Example 1 are not performed, and the steps are as follows:

[0173] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0174] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h.

[0175] (3) Pour the graphite waste residue after the above heat treatment into a treatment liquid containing inorganic acid and hydrogen peroxide, the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. High-pressure acid leaching treatment is carried out in the treatment liquid, the liquid-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2.0 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and solid-liquid separation is performed to obtain graphite material A.

[0176] (4) Graphite material A is dried at 120°C for 12 h to obtain dried high-purity graphite, and the high-purity graphite and a certain proportion of asphalt (the proportion is the same as in Example 1) are mixed evenly in a high-speed mixer, the particle size of the asphalt is D50=2-3 μm, the softening point of the asphalt is about 250°C, the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0177] (5) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain a graphite product.

[0178] Comparative Example 4

[0179] The difference between Comparative Example 4 and Example 1 is mainly that the high pressure acid leaching treatment in step (3) of Example 1 is replaced by conventional acid leaching treatment, and the steps are as follows:

[0180] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0181] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h.

[0182] (3) Pour the graphite waste residue after the above heat treatment into a treatment liquid containing an inorganic acid and hydrogen peroxide, wherein the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, and the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. Perform conventional acid leaching in the treatment liquid, the liquid-to-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the acid leaching is 80°C, the reaction time is 24 h, and the graphite material A is obtained by solid-liquid separation.

[0183] (4) The graphite obtained by the solid-liquid separation is prepared into a slurry in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0184] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0185] (6) Graphite material B is dried at 120°C for 12 h to obtain dried high-purity graphite, and the high-purity graphite and a certain proportion of asphalt (the proportion is the same as in Example 1) are mixed evenly in a high-speed mixer, the particle size of the asphalt is D50 = 2 to 3 μm, the softening point of the asphalt is about 250°C, the rotation speed of the high-speed mixer is 1500 rpm, and the mixing time in the high-speed mixer is 15 min.

[0186] (7) The mixture mixed with asphalt is carbonized in a carbonization furnace, the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain a graphite product.

[0187] Comparative Example 5

[0188] The difference between Comparative Example 5 and Example 1 is that the asphalt is not coated, and the steps are as follows:

[0189] (1) Drying the graphite waste slag at 120° C. for 12 h to obtain dried graphite waste slag; adding 5% NaOH to the dried graphite waste slag and mixing them evenly in a high-speed mixer at a mixing speed of 1500 rpm and a mixing time of 15 min.

[0190] (2) The above-mentioned graphite waste slag mixed with NaOH is heat-treated in an inert atmosphere at a temperature of 950° C. and a holding time of 6 h.

[0191] (3) Pour the graphite waste residue after the above heat treatment into a treatment liquid containing inorganic acid and hydrogen peroxide, the total concentration of the inorganic acid in the treatment liquid is 2 mol / L, the inorganic acid is a mixed acid of sulfuric acid and hydrochloric acid, the molar ratio of sulfuric acid to hydrochloric acid is 1:1; the concentration of hydrogen peroxide in the treatment liquid is 0.2 mol / L. High-pressure acid leaching treatment is carried out in the treatment liquid, the liquid-solid ratio of the acid leaching is 6 mL / g, the reaction temperature of the high-pressure acid leaching is 180°C, the reaction pressure is 1.5-2.0 MPa, the reaction time is 2 h, and after heat and pressure maintenance, the temperature is reduced and the pressure is released, and solid-liquid separation is performed to obtain graphite material A.

[0192] (4) The graphite obtained by the solid-liquid separation is prepared into a slurry in a container of a three-blade propeller stirrer. The slurry is prepared according to a solid content of 15%, and the particles in the slurry are dispersed in the container at a rotation speed of 1000 rpm for 30 minutes.

[0193] (5) The graphite slurry in the container is supplied to the spiral centrifuge by a peristaltic pump, and the agitator system is controlled to stir the slurry in the container at a speed of 600 rpm. The centrifugal acceleration of the spiral centrifuge is controlled, and the corresponding centrifugal speed is 4000 rpm. After centrifugation, the separated and purified graphite material B is collected.

[0194] (6) The graphite material B separated and purified above is subjected to heat treatment, and the heating rate of the carbonization furnace is controlled to be 2-5°C / min, the carbonization insulation temperature is 1200°C, and the carbonization insulation time is 3h. After the carbonization treatment, it is screened and demagnetized to finally obtain a graphite product.

[0195] Test Example 1

[0196] The physical and chemical properties of the graphite products prepared in the test examples and comparative examples are as follows:

[0197] Table 1 is a comparison of the impurity element contents of Examples 1-13 and Comparative Examples 1-5:

[0198] Table 1 Graphite impurity element content (ppm)

[0199]

[0200]

[0201] Table 2 shows the test results of tap density, ash content, and specific surface area of ​​the finished graphite of Examples 1-13 and Comparative Examples 1-5:

[0202] Table 2 Tap density, ash content, and specific surface area of ​​finished graphite

[0203]

[0204]

[0205] The button cells were assembled and the electrical performance was tested under the following conditions: test voltage 0-2V, constant current charge and discharge, rate 0.1C. Table 3 is a comparison of the first delithiation specific capacity and coulombic efficiency of the graphite samples prepared in Examples 1-13 and Comparative Examples 1-5:

[0206] Table 3 Delithiation specific capacity and coulombic efficiency test data of graphite samples

[0207] sample <![CDATA[Specific delithiation capacity (mAh g -1 )]]> Coulomb efficiency (%) Example 1 351.12 93.3 Example 2 351.46 93.2 Example 3 352.01 93.4 Example 4 351.43 93.2 Example 5 351.08 93.3 Example 6 350.93 93.3 Example 7 351.54 93.2 Example 8 351.45 93.3 Example 9 351.49 93.3 Example 10 351.58 93.4 Embodiment 11 352.12 93.4 Example 12 351.69 93.3 Example 13 352.10 93.5 Comparative Example 1 343.67 90.6 Comparative Example 2 342.58 89.8 Comparative Example 3 349.56 92.4 Comparative Example 4 350.25 92.5 Comparative Example 5 352.16 92.1

[0208] The results show that compared with Comparative Examples 1, 2, and 4, the impurity elements and ash content of the embodiment are much lower; although the impurity elements and ash content levels of the embodiment and Comparative Example 3 are comparable, since Comparative Example 3 does not centrifuge to separate the carbon black and amorphous carbon, it exhibits a higher specific surface area; compared with Comparative Example 5, although the impurity elements and ash content levels of the embodiment and Comparative Example 5 are comparable, since Comparative Example 5 does not undergo asphalt coating treatment, the defects are not fully repaired, exhibiting a higher specific surface area.

[0209] Therefore, the graphite product prepared in the embodiment of the present invention has a lower ash content, a higher tap density and a lower specific surface area; and after reducing impurities, removing carbon black and amorphous carbon, the ash content of the embodiment reaches battery-grade graphite, and the electrical properties are excellent.

[0210] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for regenerating and repairing graphite waste residue after wet lithium extraction from waste lithium batteries, characterized in that: include: The graphite waste residue is mixed with an inorganic strong base or a carbonate, and then subjected to heat treatment to obtain a first graphite material; The first graphite material is mixed with a treatment solution containing an inorganic acid and an oxidant, and subjected to high-pressure acid leaching, and a second graphite material is obtained after solid-liquid separation; Mixing the second graphite material and water to prepare a slurry to obtain a graphite slurry; The graphite slurry is passed into a spiral centrifuge for centrifugal separation to obtain a third graphite material.

2. The regeneration and repair method according to claim 1, characterized in that: In the process of preparing the first graphite material, the heat treatment temperature is 800° C.-1200° C., and the heat preservation time is 2 h-10 h; and / or, heat treatment is performed under an inert atmosphere.

3. The regeneration and repair method according to claim 1 or 2, characterized in that: The inorganic strong base is selected from at least one of sodium hydroxide and potassium hydroxide, and the mass ratio of the graphite waste slag to the inorganic strong base is 100:(3-10); And / or, the carbonate is selected from at least one of sodium carbonate and potassium carbonate, and the mass ratio of the graphite waste slag to the carbonate is 100:(3-10); And / or, the graphite waste slag is first dried and then mixed with an inorganic strong base or carbonate, and the drying temperature is controlled to be 80° C.-200° C. and the drying time is 10 h-30 h.

4. The regeneration and repair method according to claim 1, characterized in that: In the process of preparing the second graphite material, the reaction temperature of the high-pressure acid leaching is 110° C.-180° C., the reaction pressure is 1 MPa-2 MPa, the reaction time is 60 min-36 h, and then the temperature is reduced and the pressure is released before solid-liquid separation; And / or, the inorganic acid in the treatment solution is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid.

5. The regeneration and repair method according to claim 4, characterized in that: The inorganic acid in the treatment liquid is a mixed acid, and the mixed acid includes sulfuric acid; and / or, the oxidant in the treatment liquid is hydrogen peroxide; And / or, the concentration of the inorganic acid in the treatment solution is 1 mol / L-5 mol / L, and the concentration of the oxidant is 0.1 mol / L-0.5 mol / L.

6. The regeneration and repair method according to claim 1, characterized in that: The solid content of the graphite slurry is 10%-30%; And / or, the preparation process of the graphite slurry includes: mixing the second graphite material and water, and dispersing the particles in the slurry at a rotation speed of 600 rpm-1000 rpm for 30 min-60 min.

7. The regeneration and repair method according to claim 1, characterized in that: In the process of separating the third graphite material from the graphite slurry, the stirring speed of the spiral centrifuge is controlled to be 300rpm-600rpm, the centrifugal speed is controlled to be 2500rpm-4500rpm, and the separated and purified graphite material is collected after centrifugation.

8. The regeneration and repair method according to claim 1, characterized in that: Also includes: Mixing the third graphite material with a coating agent to obtain a mixture, and carbonizing the mixture; Wherein, the coating agent is selected from at least one of asphalt and phenolic resin.

9. The regeneration and repair method according to claim 8, characterized in that: The third graphite material is dried and then mixed with the coating agent, and the mass ratio of the graphite material to the coating agent is controlled to be 100:(2-10); and / or, during the mixing process with the coating agent, the stirring speed is controlled to be 1000 rpm-2000 rpm, and the mixing time is 10 min-30 min; And / or, the coating agent is asphalt, the particle size D50 of the asphalt is 2 μm-6 μm, and the softening point of the asphalt is 230° C.-260° C.; And / or, the drying temperature of the third graphite material is 80° C.-200° C., and the drying time is 10 h-30 h.

10. The regeneration and repair method according to claim 8, characterized in that: During the carbonization treatment of the mixture, the carbonization temperature is controlled to be 900° C.-1400° C. and the insulation time is 1 h-5 h; And / or, the temperature is raised to the carbonization temperature at a heating rate of 2°C / min-5°C / min.

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