A method for regenerating waste ternary cathode materials

Abstract

The present invention discloses a method for regenerating waste ternary cathode materials, comprising the following steps: (1) mixing the waste ternary cathode materials with an acid for activation; (2) mixing the activated cathode materials with a lithium source solution, supplementing lithium under pressurized heating conditions, and annealing the supplemented cathode materials in an inert atmosphere; (3) mixing the annealed cathode materials, a nickel source, a cobalt source, a manganese source, a fluoride, and water to obtain a mixture, spray granulating the mixture to obtain an NCM precursor, calcining the NCM precursor in an oxygen atmosphere to obtain a calcined material; and (4) pre-coating the calcined material in a liquid phase with porous graphene loaded with coating particles, calcining the obtained pre-coated material in an oxygen atmosphere to obtain a coated ternary cathode material. The present invention effectively improves the purity, structural stability, and electrochemical performance of the regenerated ternary cathode material through annealing, doping, gradient calcination, and coating.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion positive electrode material recovery, and in particular to a method for regenerating waste ternary positive electrode materials. Background Art

[0002] Lithium-ion batteries are secondary battery systems that use two different lithium-intercalating compounds that can reversibly insert and remove lithium ions as the positive and negative electrodes, respectively. During charging, lithium ions are removed from the positive electrode material's lattice, then inserted into the negative electrode material's lattice after passing through the electrolyte, making the negative electrode lithium-rich and the positive electrode lithium-poor. During discharge, lithium ions are removed from the negative electrode material's lattice, then inserted into the positive electrode material's lattice after passing through the electrolyte, making the positive electrode lithium-rich and the negative electrode lithium-poor. The difference in potential between the positive and negative electrode materials relative to metallic lithium during lithium ion insertion and extraction is the battery's operating voltage.

[0003] At present, a large number of lithium-ion batteries are discarded. Discarded lithium-ion batteries contain a large amount of non-renewable and economically valuable metal resources, such as cobalt, lithium, nickel, copper, aluminum, etc. If discarded or unqualified lithium-ion batteries can be effectively recycled and processed, it will not only reduce the pressure of waste batteries on the environment, but also prevent the waste of metal resources such as cobalt and nickel.

[0004] The main industrial recycling methods for waste ternary lithium-ion batteries are pyrolysis and wet processing. The pyrolysis method directly recycles battery materials through high-temperature treatment. Its process is relatively simple, but the recovery rate is low and the high-temperature treatment time is long, the energy consumption is high, and organic matter such as electrolytes and binders will produce harmful gases at high temperatures, causing environmental pollution. The wet method is to disassemble the battery shell, crush and screen it, and then leach the valuable metals in the electrode material, and then perform precipitation separation or extraction separation to obtain the corresponding salts or oxides of each metal to achieve battery material recycling, but the process is more complicated. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for regenerating waste ternary cathode materials. This method, after lithium supplementation and high-temperature annealing, makes the atomic arrangement of the material more compact, reduces the interatomic distance, and thus refines the grains, thereby improving the crystallinity of the material. Then, by fluoride doping in the material, the material's cation mixing is reduced, the material's structure is stabilized, and the cycle and rate performance are improved. Finally, by coating the ternary cathode material, the ternary cathode material is isolated from the electrolyte, reducing side reactions and slowing down the collapse of the electrode material.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A method for regenerating waste ternary cathode materials comprises the following steps:

[0008] S1: Mixing the waste ternary cathode material with acid for activation;

[0009] S2: mixing the activated cathode material with a lithium source solution, replenishing lithium under pressurized heating conditions, and annealing the cathode material after replenishing lithium in an inert atmosphere;

[0010] S3: mixing the annealed positive electrode material, nickel source, cobalt source, manganese source, fluoride and water to obtain a mixture, spray granulating the mixture to obtain an NCM precursor, and calcining the NCM precursor in an oxygen atmosphere to obtain a calcined material;

[0011] S4: liquid-phase pre-coating the calcined material with porous graphene loaded with coating particles, and calcining the obtained pre-coated material in an oxygen atmosphere to obtain a coated ternary positive electrode material.

[0012] In some embodiments of the present invention, the waste ternary positive electrode material in step S1 is prepared by the following steps: disassembling the waste ternary lithium battery, taking out the positive electrode sheet, and performing alkaline leaching, solid-liquid separation, drying, calcining, and grinding on the positive electrode sheet to obtain the waste ternary positive electrode material.

[0013] In some embodiments of the present invention, the acid in step S1 is at least one of acetic acid, tartaric acid, malic acid or citric acid.

[0014] In some preferred embodiments of the present invention, the pH of the acid in step S1 is 3-5.

[0015] In some embodiments of the present invention, the lithium source in step S2 is at least one of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium chloride or lithium bromide.

[0016] In some embodiments of the present invention, the annealing temperature in step S2 is 500-950° C., and the annealing time is 1-3 hours.

[0017] In some preferred embodiments of the present invention, the annealing temperature in step S2 is 700-900° C., and the annealing time is 1-3 hours.

[0018] In some embodiments of the present invention, the nickel source described in step S3 is at least one of NiC4H6O4·4H2O or Ni(NO3)2·6H2O; the cobalt source is at least one of CoC4H6O4·4H2O or Co(NO3)2·6H2O; and the manganese source is at least one of MnC4H6O4·4H2O or Mn(NO3)2·6H2O.

[0019] In some embodiments of the present invention, the fluoride in step S3 is at least one of ammonium fluoride, aluminum fluoride, sodium fluoride or potassium fluoride, and the molar ratio of the positive electrode material to the fluoride is 1:(0.001-0.05).

[0020] In some preferred embodiments of the present invention, the fluoride described in step S3 is aluminum fluoride, and the molar ratio of the positive electrode material to aluminum fluoride is 1: (0.005-0.03). As the preferred aluminum fluoride, aluminum ions are used to partially replace the positions of transition metal ions, thereby reducing the effect of cation mixing.

[0021] In some embodiments of the present invention, the calcination temperature in step S3 is 800-950° C., and the calcination time is 8-16 hours.

[0022] In some embodiments of the present invention, the coating material in step S4 is porous graphene, and the porous graphene carries at least one of lithium salt, SiO2, AlF3, Al2O3, iron phosphate, ZrO2 or V2O5.

[0023] In some embodiments of the present invention, the preparation method of the porous graphene loaded with coated particles described in step S4 is as follows: adding the porous graphene to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide, and ultrasonically dispersing it evenly; stirring in a water bath, then adding tetraethyl silicate dropwise, continuing the reaction, centrifuging, filtering, and drying overnight; the above product is reacted at high temperature in argon, and naturally cooled to room temperature to obtain a composite material.

[0024] In some preferred embodiments of the present invention, the coating material in step S4 is porous graphene, and the porous graphene is loaded with SiO2.

[0025] In some embodiments of the present invention, the NCM precursor described in step S3 is coated by spraying.

[0026] In some embodiments of the present invention, the multi-gradient calcination in step S4 includes a primary calcination and a secondary calcination, wherein the primary calcination has a heating rate of 1-6°C / min, a temperature of 400-500°C, and a time of 4-6 hours; and the secondary calcination has a heating rate of 1-6°C / min, a temperature of 800-950°C, and a time of 8-16 hours.

[0027] According to a preferred embodiment of the present invention, there are at least the following beneficial effects:

[0028] 1. Annealing treatment is performed after hydrothermal lithium replenishment to make the atomic arrangement closer, reduce the atomic distance and thus refine the grains, thereby improving the crystallinity of the material, the stability of the crystal structure and the electrochemical properties.

[0029] 2. By using fluoride doping, fluorine can replace part of the oxygen in the lattice to reduce the redox activity of oxygen and stabilize the structure, thereby improving the cycle and rate performance of the material.

[0030] 3. As a preference, the present invention adopts gradient calcination, which can effectively slow down the crystal transformation rate of the ternary positive electrode material during calcination, reduce lattice defects, and improve the integrity and stability of the material.

[0031] 4. By coating the surface of the ternary positive electrode material, the active material in the battery can be physically isolated from the electrolyte, reducing the occurrence of side reactions and inhibiting the dissolution of transition metal ions in the electrolyte. At the same time, the inactive coating layer with a certain mechanical strength can also slow down the collapse of the electrode material structure during long-term cycling.

[0032] 5. The present invention pre-prepares graphene loaded with a coating. The coating particles are small in size and are evenly dispersed and loaded on the graphene without agglomeration. The graphene loaded with the coating particles is coated on the positive electrode material by spraying. During subsequent aerobic sintering, the graphene is converted into carbon dioxide, and the loaded particles are evenly coated on the ternary positive electrode material. Compared with the conventional solid-phase mixed coating method, the coating material is more evenly distributed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0034] Figure 1 This is a SEM image of the NCM precursor prepared in Example 1 of the present invention;

[0035] Figure 2 This is a SEM image of the coated ternary cathode material prepared in Example 1 of the present invention;

[0036] Figure 3 This is a comparison chart of the XRD patterns of the calcined materials described in Example 1 of the present invention and Comparative Example 1;

[0037] Figure 4 This is the EDS diagram of element distribution after AlF3 doping obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for regenerating waste ternary cathode materials comprises the following steps:

[0041] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 30% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 90°C, stir for 1.5h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0042] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0043] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0044] Step 4: adding the powder obtained in step 3 to acetic acid with a pH value of 4.0, stirring at 50° C. for 1 hour, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0045] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0046] Step 6: Add the activated cathode material to a 4 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:20 mL, and heat under high pressure, sealed, and nitrogen atmosphere at a heating temperature of 280° C. for 5 h.

[0047] Step 7: After lithium replenishment, the mixture is filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 900°C, and kept warm for 2 hours in flowing nitrogen;

[0048] Step 8, the annealed positive electrode material is added to the filter residue according to the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=5:2:3, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0049] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM523 precursor;

[0050] Step 10, placing the NCM523 precursor prepared in step 9 into a muffle furnace, calcining it with industrial oxygen, raising the temperature to 850° C., and keeping the temperature for 10 hours to obtain a calcined material;

[0051] Step 11, preparing silica-loaded graphene: The porous graphene is added to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide and uniformly dispersed by ultrasonication. Stirring is performed in a water bath, and tetraethyl silicate is then added dropwise. The reaction is continued, followed by centrifugation, filtration, and drying overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain a composite material.

[0052] Step 12, adding water according to the mass volume ratio of the composite material prepared in step 11 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a composite material suspension;

[0053] Step 13, spraying the suspension prepared in step 12 on the calcined material described in step 10 by spraying, stirring and mixing at a stirring speed of 60 rpm and a stirring time of 20 minutes, and performing a total of three times to obtain a pre-coated NCM precursor with a silica mass percentage of 0.5%;

[0054] In step 14, the pre-coated NCM precursor prepared in step 13 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 500°C and kept warm for 5 hours, then the temperature is raised to 900°C and kept warm for 12 hours to obtain the regenerated ternary positive electrode material NCM523.

[0055] Figure 2 This is an SEM image of the coated ternary positive electrode material prepared in Example 1 of the present invention. It can be seen from the figure that the coating effect of the ternary positive electrode material prepared in this example is good.

[0056] Figure 4 This is the EDS diagram of element distribution after AlF3 doping obtained in Example 1 of the present invention. It can be seen from the figure that Ni, Co, Mn, and F elements are evenly distributed, indicating that the material has good uniformity.

[0057] Example 2

[0058] A method for regenerating waste ternary cathode materials comprises the following steps:

[0059] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 40% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 70°C, stir for 2h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0060] Step 2, washing the leached residue with pure water and drying at 100° C. for 12 h;

[0061] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0062] Step 4: adding the powder obtained in step 3 to malic acid with a pH of 3.0, stirring at 30° C. for 2 h, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0063] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0064] Step 6: Add the activated cathode material to a 3 mol / L lithium carbonate solution at a solid-liquid ratio of 1 g:20 mL, and heat under a nitrogen atmosphere at 300° C. for 6 h.

[0065] Step 7: After lithium replenishment, the mixture was filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 800°C, and kept warm in flowing nitrogen for 1 hour;

[0066] Step 8, the annealed positive electrode material is added to the filter residue according to the ratio of the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=6:2:2, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0067] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM622 precursor;

[0068] Step 10, placing the NCM622 precursor prepared in step 9 into a muffle furnace, calcining it with industrial oxygen, raising the temperature to 850° C., and keeping the temperature for 10 hours to obtain a calcined material;

[0069] Step 11, preparing silica-loaded graphene: The porous graphene is added to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide and uniformly dispersed by ultrasonication. Stirring is performed in a water bath, and tetraethyl silicate is then added dropwise. The reaction is continued, followed by centrifugation, filtration, and drying overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain a composite material.

[0070] Step 12, adding water according to the mass volume ratio of the composite material prepared in step 11 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a composite material suspension;

[0071] Step 13, spraying the suspension prepared in step 12 on the calcined material described in step 10 by spraying, stirring and mixing at a stirring speed of 60 rpm and a stirring time of 20 minutes, and performing a total of three times to obtain a pre-coated NCM precursor with a silica mass percentage of 0.5%;

[0072] In step 14, the pre-coated NCM precursor prepared in step 13 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 400°C and kept for 6 hours, then the temperature is raised to 800°C and kept for 16 hours to obtain the regenerated ternary positive electrode material NCM622.

[0073] Example 3

[0074] A method for regenerating waste ternary cathode materials comprises the following steps:

[0075] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 40% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 70°C, stir for 2h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0076] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0077] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0078] Step 4: adding the powder obtained in step 3 to tartaric acid with a pH of 5.0, stirring at 30° C. for 2 h, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0079] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0080] Step 6: Add the activated cathode material to a 5 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:40 mL, and heat under a nitrogen atmosphere at 280° C. for 5 h.

[0081] Step 7: After lithium replenishment, the mixture was filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 800°C, and kept warm in flowing nitrogen for 1 hour;

[0082] Step 8, the annealed positive electrode material is added to the filter residue according to the ratio of the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=6:2:2, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0083] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM622 precursor;

[0084] Step 10, placing the NCM622 precursor prepared in step 9 into a muffle furnace, calcining it with industrial oxygen, raising the temperature to 850° C., and keeping the temperature for 10 hours to obtain a calcined material;

[0085] Step 11, preparing silica-loaded graphene: The porous graphene is added to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide and uniformly dispersed by ultrasonication. Stirring is performed in a water bath, and tetraethyl silicate is then added dropwise. The reaction is continued, followed by centrifugation, filtration, and drying overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain a composite material.

[0086] Step 12, adding water according to the mass volume ratio of the composite material prepared in step 11 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a composite material suspension;

[0087] Step 13, spraying the suspension prepared in step 12 onto the calcined material in step 10 while stirring and mixing at a stirring speed of 100 rpm for 20 minutes, and performing the process three times to obtain a pre-coated NCM precursor having a silica mass percentage of 0.5%;

[0088] In step 14, the pre-coated NCM precursor prepared in step 13 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 500°C and kept for 6 hours, then the temperature is raised to 850°C and kept for 16 hours to obtain the regenerated ternary positive electrode material NCM622.

[0089] Comparative Example 1

[0090] A method for regenerating waste ternary cathode materials, which differs from Example 1 only in that no annealing operation is performed, and other conditions remain unchanged, comprises the following steps:

[0091] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 30% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 90°C, stir for 1.5h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0092] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0093] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0094] Step 4: adding the powder obtained in step 3 to acetic acid with a pH value of 4.0, stirring at 50° C. for 1 hour, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0095] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0096] Step 6: Add the activated cathode material to a 4 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:20 mL, and heat under high pressure, sealed, and nitrogen atmosphere at a heating temperature of 280° C. for 5 h.

[0097] Step 7, the annealed positive electrode material is added to the filter residue according to the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=5:2:3, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0098] Step 8: Add the suspension obtained in step 7 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM523 precursor;

[0099] Step 9: Place the NCM523 precursor prepared in step 8 into a muffle furnace, add industrial oxygen for calcination, raise the temperature to 850° C., and keep the temperature for 10 hours to obtain a calcined material;

[0100] Step 10, preparing silica-loaded graphene: The porous graphene is added to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide and uniformly dispersed by ultrasonication. Stirring is performed in a water bath, and tetraethyl silicate is then added dropwise. The reaction is continued, followed by centrifugation, filtration, and drying overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain a composite material.

[0101] Step 11, adding water according to the mass volume ratio of the composite material prepared in step 10 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a composite material suspension;

[0102] Step 12, spraying the suspension prepared in step 12 onto the calcined material described in step 9 by spraying, while stirring and mixing, the stirring speed is 60 rpm, the stirring time is 20 minutes, and a total of three times are performed to obtain a pre-coated NCM precursor with a silica mass percentage of 0.5%;

[0103] In step 13, the coated NCM precursor prepared in step 12 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 500°C and kept warm for 5 hours, then the temperature is raised to 900°C and kept warm for 12 hours to obtain the regenerated ternary positive electrode material NCM523.

[0104] Figure 3 This is an XRD comparison diagram of the coated ternary positive electrode material obtained in Example 1 and Comparative Example 1. It can be seen from the figure that the diffraction peak intensity of the ternary positive electrode material obtained in Example 1 is larger, that is, the annealing operation improves the purity and crystallinity of the ternary positive electrode material, thereby improving the stability of the material.

[0105] Comparative Example 2

[0106] A method for regenerating waste ternary cathode materials, which differs from Example 1 only in that AlF3 doping is not added, and other conditions remain unchanged, comprises the following steps:

[0107] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 30% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 90°C, stir for 1.5h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0108] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0109] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0110] Step 4: adding the powder obtained in step 3 to acetic acid with a pH value of 4.0, stirring at 50° C. for 1 hour, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0111] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0112] Step 6: Add the activated cathode material to a 4 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:20 mL, and heat under high pressure, sealed, and nitrogen atmosphere at a heating temperature of 280° C. for 5 h.

[0113] Step 7: After lithium replenishment, the mixture is filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 900°C, and kept warm for 2 hours in flowing nitrogen;

[0114] Step 8, the annealed positive electrode material is added to the filter residue according to the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=5:2:3, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0115] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM523 precursor;

[0116] Step 10, placing the NCM523 precursor prepared in step 9 into a muffle furnace, calcining it with industrial oxygen, raising the temperature to 850° C., and keeping the temperature for 10 hours to obtain a calcined material;

[0117] Step 11, preparing silica-loaded graphene: The porous graphene is added to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide and uniformly dispersed by ultrasonication. Stirring is performed in a water bath, and tetraethyl silicate is then added dropwise. The reaction is continued, followed by centrifugation, filtration, and drying overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain a composite material.

[0118] Step 12, adding water according to the mass volume ratio of the composite material prepared in step 11 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a composite material suspension;

[0119] Step 13, spraying the suspension prepared in step 12 on the calcined material described in step 10 by spraying, stirring and mixing at a stirring speed of 60 rpm and a stirring time of 20 minutes, and performing a total of three times to obtain a pre-coated NCM precursor with a silica mass percentage of 0.5%;

[0120] In step 14, the pre-coated NCM precursor prepared in step 13 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 500°C and kept warm for 5 hours, then the temperature is raised to 900°C and kept warm for 12 hours to obtain the regenerated ternary positive electrode material NCM523.

[0121] Comparative Example 3

[0122] A method for regenerating waste ternary cathode materials, which differs from Example 1 only in that no coating operation is performed, and other conditions remain unchanged, comprises the following steps:

[0123] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 30% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 90°C, stir for 1.5h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0124] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0125] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0126] Step 4: adding the powder obtained in step 3 to acetic acid with a pH value of 4.0, stirring at 50° C. for 1 hour, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0127] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0128] Step 6: Add the activated cathode material to a 4 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:20 mL, and heat under high pressure, sealed, and nitrogen atmosphere at a heating temperature of 280° C. for 5 h.

[0129] Step 7: After lithium replenishment, the mixture is filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 900°C, and kept warm for 2 hours in flowing nitrogen;

[0130] Step 8, the annealed positive electrode material is added to the filter residue according to the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=5:2:3, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0131] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM523 precursor;

[0132] Step 10: Place the spherical NCM precursor prepared in step 9 into a muffle furnace and perform two-stage calcination using industrial oxygen. First, heat it to 500°C and keep it warm for 5 hours, then heat it to 900°C and keep it warm for 12 hours to obtain the regenerated ternary positive electrode material NCM523.

[0133] Comparative Example 4

[0134] A method for regenerating waste ternary cathode materials, which differs from Example 1 only in that the pre-coating does not include graphene, and other conditions remain unchanged, comprises the following steps:

[0135] Step 1: After disassembling the waste ternary lithium battery, take out the positive electrode sheet, put the positive electrode sheet into a 30% by mass sodium hydroxide solution according to a solid-liquid ratio of 10g / L, control the temperature to 90°C, stir for 1.5h, and after the residual aluminum foil is completely dissolved, separate the solid and liquid to obtain a leachate and a leach residue;

[0136] Step 2, washing the leached residue with pure water and drying at 110° C. for 10 h;

[0137] Step 3, calcining the dried leached residue at 500° C. in an oxygen atmosphere for 5 h, and grinding the mixture to obtain a powder after cooling;

[0138] Step 4: adding the powder obtained in step 3 to acetic acid with a pH value of 4.0, stirring at 50° C. for 1 hour, and then performing solid-liquid separation to obtain a solid material and a filtrate;

[0139] Step 5, washing the solid material obtained in step 4 with pure water to obtain an activated positive electrode material;

[0140] Step 6: Add the activated cathode material to a 4 mol / L lithium hydroxide solution at a solid-liquid ratio of 1 g:20 mL, and heat under high pressure, sealed, and nitrogen atmosphere at a heating temperature of 280° C. for 5 h.

[0141] Step 7: After lithium replenishment, the mixture is filtered and dried in a vacuum oven at 80°C, then transferred to a tube furnace, heated to 900°C, and kept warm for 2 hours in flowing nitrogen;

[0142] Step 8, the annealed positive electrode material is added to the filter residue according to the total molar amount of nickel, cobalt and manganese to the molar amount of lithium of 1:1.08, and at the same time according to Ni:Co:Mn=5:2:3, NiC4H6O4·4H2O, CoC4H6O4·4H2O, and MnC4H6O4·4H2O, and then AlF3 is added according to the molar ratio of the positive electrode material to AlF3 of 1:0.03, and then water is added according to the mass volume ratio of the mixture to water of 0.3g:1mL. After ultrasonication for 10min, a mixed suspension with uniform composition is obtained;

[0143] Step 9: Add the suspension obtained in step 8 to a spray dryer, control the temperature of the spray dryer to 180° C., the feed rate to 450 mL / h, the inlet pressure to 0.5 MPa, and the outlet temperature to 150° C., and perform spray granulation to continuously prepare a spherical NCM523 precursor;

[0144] Step 10, placing the NCM523 precursor prepared in step 9 into a muffle furnace, calcining it with industrial oxygen, raising the temperature to 850° C., and keeping the temperature for 10 hours to obtain a calcined material;

[0145] Step 11: Tetraethyl silicate is added dropwise to deionized water containing hexadecyltrimethylammonium bromide and sodium hydroxide, stirred in a water bath, and the reaction is continued. The mixture is centrifuged, filtered, and then dried overnight. The product is reacted at high temperature in an argon atmosphere and naturally cooled to room temperature to obtain silica.

[0146] Step 12: adding water according to the mass volume ratio of the silica prepared in step 11 to water at 1 g:100 mL, and ultrasonicating for 10 minutes to obtain a silica suspension;

[0147] Step 13, spraying the suspension prepared in step 12 on the calcined material described in step 10 by spraying, stirring and mixing at a stirring speed of 60 rpm and a stirring time of 20 minutes, and performing a total of three times to obtain a pre-coated NCM precursor with a silica mass percentage of 0.5%;

[0148] In step 14, the pre-coated NCM precursor prepared in step 13 is placed in a muffle furnace and calcined in two stages using industrial oxygen. First, the temperature is raised to 500°C and kept warm for 5 hours, then the temperature is raised to 900°C and kept warm for 12 hours to obtain the regenerated ternary positive electrode material NCM523.

[0149] Test example

[0150] The first efficiency, discharge capacity, and 200-cycle retention of the ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested using button-type batteries at 25°C. The test conditions were: 2.8-4.25V, 0.1C charge and discharge, using a LAND charge-discharge instrument.

[0151] Table 1 Electrochemical performance test data of the embodiments of the present invention and the comparative examples:

[0152]

[0153] As shown in Table 1, the first coulombic efficiency of the ternary cathode material prepared by the present invention is above 90%, and the discharge capacity reaches 173 mAh g -1 As shown above, the 200-cycle capacity retention rate reaches more than 90%, indicating that the regenerated ternary cathode material of the present invention has good electrochemical performance.

[0154] The difference between Comparative Example 1 and Example 1 is that the ternary positive electrode material prepared in Comparative Example 1 has not undergone annealing operation, and its purity, crystallinity and stability are not as good as those in Example 1, so the discharge capacity is lower.

[0155] The difference between Comparative Example 2 and Example 1 is that the ternary positive electrode material prepared in Comparative Example 2 is not doped with AlF3, which cannot reduce the cation mixing of the recycled ternary positive electrode material, and thus the first coulombic efficiency and cycle performance are low.

[0156] The difference between Comparative Example 3 and Example 1 is that the ternary positive electrode material prepared in Comparative Example 3 is not coated, and the active substance therein will have a side reaction with the electrolyte, thereby affecting the capacity and electrode structure of the battery, while Examples 1-3 all use graphene loaded with a coating, which is coated on the positive electrode material by spraying. During subsequent aerobic sintering, the graphene is converted into carbon dioxide, and the loaded particles are evenly coated on the ternary positive electrode material. Compared with the conventional solid-phase mixed coating method, the coating material is more evenly distributed, thereby obtaining better cycle performance.

[0157] The difference between Comparative Example 4 and Example 1 is that the silicon dioxide used for coating is not loaded on graphene. As can be seen from Table 1, the cycle performance is relatively low, indicating that the coating effect of silicon dioxide is worse than that of the composite material formed when loaded on graphene.

[0158] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for regenerating waste ternary cathode materials, characterized in that: The following steps are involved: S1: Mixing the waste ternary cathode material with acid for activation; S2: mixing the activated cathode material with a lithium source solution, replenishing lithium under pressurized heating conditions, and annealing the cathode material after replenishing lithium in an inert atmosphere; S3: mixing the annealed positive electrode material, nickel source, cobalt source, manganese source, fluoride and water to obtain a mixture, spray granulating the mixture to obtain an NCM precursor, and calcining the NCM precursor in an oxygen atmosphere to obtain a calcined material; S4: pre-coating the calcined material in a liquid phase with porous graphene loaded with coating particles, and calcining the obtained pre-coated material in an oxygen atmosphere to obtain a coated ternary cathode material; The annealing temperature in step S2 is 500-950° C. and the time is 1-3 hours; The fluoride in step S3 is aluminum fluoride, and the molar ratio of the positive electrode material after annealing to the aluminum fluoride is 1:(0.001-0.05).

2. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The acid in step S1 is at least one of acetic acid, tartaric acid, malic acid or citric acid.

3. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The lithium source solution in step S2 is a solution containing at least one of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium chloride or lithium bromide.

4. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The nickel source described in step S3 is at least one of NiC4H6O4·4H2O or Ni(NO3)2·6H2O; the cobalt source is at least one of CoC4H6O4·4H2O or Co(NO3)2·6H2O; and the manganese source is at least one of MnC4H6O4·4H2O or Mn(NO3)2·6H2O.

5. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The calcination temperature in step S3 is 800-950° C. and the calcination time is 8-16 hours.

6. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The coating particles in step S4 are at least one of lithium salt, SiO2, AlF3, Al2O3, iron phosphate, ZrO2 or V2O5.

7. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: In step S3, the pre-coating process is as follows: the porous graphene loaded with coated particles is mixed with water to form a suspension, the suspension is sprayed on the calcined material in a spraying manner, and the calcined material is stirred at the same time to obtain the pre-coated material.

8. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that: The calcination in step S4 adopts multi-gradient calcination, including primary calcination and secondary calcination. The primary calcination has a heating rate of 1-6°C / min, a temperature of 400-500°C, and a time of 4-6h; the secondary calcination has a heating rate of 1-6°C / min, a temperature of 800-950°C, and a time of 8-16h.

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