Titanium layer construction repair cooperates with low eutectic salt to regenerate waste nickel cobalt manganese lithium cathode material

Abstract

This invention provides a titanium-layer-constructed, synergistic low-eutectic salt regenerated waste lithium nickel cobalt manganese oxide cathode material. The preparation method includes the following steps: cutting the electrode sheet and placing it in an N-methylpyrrolidone solution, ultrasonically dissolving, filtering, washing, drying, and sieving to obtain the waste lithium nickel cobalt manganese oxide material; mixing the obtained waste lithium nickel cobalt manganese oxide cathode material with a titanium source, then adding a lithium source and mixing evenly to obtain a composite material; sintering the composite material in a two-stage process under an oxidizing atmosphere, cooling to room temperature, to obtain the regenerated waste lithium nickel cobalt manganese oxide cathode material with lithium replenishment and repair. The resulting material has a core-shell coated structure, with a lithium metatitanate layer as the coating layer and a titanium-doped lithium nickel cobalt manganese oxide core. The regenerated material exhibits uniform doping and coating, excellent rate performance, and significantly improved charge / discharge capacity and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of recycling waste nickel-cobalt-manganese lithium battery cathode materials, specifically involving a titanium layer construction repair synergistic low eutectic salt regeneration method for waste nickel-cobalt-manganese lithium battery cathode materials. Background Technology

[0002] With the increasing maturity of lithium-ion power battery research and production technology, a series of new power lithium-ion batteries, represented by ternary lithium batteries, have become a solid foundation for the rapid development of my country's electric vehicle industry. It is predicted that by 2025, the amount of retired power lithium-ion batteries from pure electric vehicles in my country will reach 464,000 tons. Lithium-ion batteries contain valuable elements such as nickel, cobalt, manganese, and lithium, as well as toxic electrolytes. If the large quantity of waste power lithium-ion batteries is not properly and efficiently disposed of and recycled, it will not only pollute the ecological environment and threaten human health, but also seriously waste resources. Currently, researchers have conducted extensive research on the recycling and reuse of waste nickel-cobalt-manganese lithium oxide batteries, but the results are unsatisfactory.

[0003] CN113921928A discloses a method for recycling heavy metals from waste lithium-ion battery cathode materials. This method uses ascorbic acid and fulvic acid in combination as a mixed acid solution to simultaneously recycle two different lithium-ion battery cathode materials in one step. Ascorbic acid releases H+ in aqueous solution and is weakly acidic, which is beneficial for leaching metal ions from the electrode materials. Fulvic acid, as a leaching agent, is easily soluble in water, and the aqueous solution is acidic. Furthermore, fulvic acid contains various active groups such as carboxyl and hydroxyl groups, which have a strong chelating ability for metal ions. The combined use of both achieves a good effect in treating the two types of lithium-ion battery cathode materials. However, this method consumes a large amount of acid and alkali leaching agents, leading to serious environmental pollution, and its commercial application prospects are not broad.

[0004] CN 113957255A discloses a method for separating and recovering valuable metals from waste ternary lithium batteries. The method includes the following steps: adding persulfate to waste ternary lithium battery powder for oxidative acid leaching to obtain a leachate and leachate residue; adding alkaline solution to the leachate for precipitation, followed by adding sulfide salt for reaction, adjusting the pH, and precipitating again to obtain nickel hydroxide precipitate and liquid phase A; adding carbonate to liquid phase A for reaction, followed by solid-liquid separation to obtain lithium carbonate; calcining the leachate residue, adding chlorate for heating, and then separating the solid and liquid to obtain manganese dioxide. However, this method has a complex process flow, difficulty in removing impurities, and low economic efficiency.

[0005] CN 113880100A discloses a method for preparing recycled ternary cathode material from lithium nickel cobalt oxide batteries, comprising the following steps: (1) discharging and disassembling waste lithium-ion batteries using sodium chloride solution, soaking the cathode sheet in alkaline solution, and filtering to obtain black powder; (2) reducing and calcining the obtained black powder under a protective atmosphere; (3) dissolving the black powder in an acidic solution, extracting and removing impurities to obtain a high-purity mixed solution containing nickel and cobalt; (4) after measuring the concentrations of cobalt and nickel ions, adding corresponding manganese and tungsten sources to the solution, adjusting the pH, and performing a co-precipitation reaction to obtain a precursor; (5) sintering the precursor with lithium and boron sources to obtain the cathode material. However, this method is complex and requires co-precipitation to re-prepare the precursor, resulting in high costs for commercial application. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a titanium layer construction repair synergistic low eutectic salt regeneration waste nickel cobalt manganese oxide cathode material with wide raw material sources, simple and controllable technology, short process flow, good repair effect, and suitable for industrialization.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A titanium-layer-constructed, repair-synergistic, low-eutectic salt-based recycled waste nickel-cobalt-manganese lithium oxide cathode material is prepared by the following steps:

[0009] (1) After cutting the electrode sheet, place it in N-methylpyrrolidone solution, dissolve it by ultrasonication, filter, wash, dry and sieve to obtain waste nickel cobalt manganese lithium oxide material.

[0010] (2) Mix the waste nickel cobalt manganese oxide lithium cathode material obtained in step (1) with the titanium source evenly, and then add the lithium source and mix evenly to obtain the composite material.

[0011] (3) The composite material obtained in step (2) is sintered in two stages under an oxidizing atmosphere and cooled to room temperature to obtain a recycled waste nickel cobalt manganese oxide cathode material for lithium replenishment and repair.

[0012] Waste cathode material is waste nickel-cobalt-manganese lithium oxide material separated from the electrode sheet; low eutectic salt short-process regeneration uses mixed lithium salts, which react at a low eutectic point after being mixed in a certain proportion; titanium layer construction repair involves adding a titanium source during the regeneration process to further construct a protective layer and repair the regenerated material. The titanium layer construction repair, in conjunction with the low eutectic salt short-process regenerated cathode material, is formed by the accumulation of primary particles and the formation of secondary agglomerates, and a uniform titanium-containing protective layer is constructed on the surface of the material.

[0013] Preferably, in step (1), the electrode sheet is obtained by discharging and dismantling a waste nickel-cobalt-manganese lithium oxide battery. Preferably, the ultrasonic dissolution process in step (1) involves immersing the electrode sheet in N-methylpyrrolidone and ultrasonicating at 30-60 kHz for 30-50 minutes at 60-80°C; the centrifugation process is at a speed of 2000-10000 r / min; the cleaning reagent is deionized water and / or anhydrous ethanol; and the drying temperature is 60-110°C. If the centrifugation speed is too low, it is not conducive to the separation of the cathode material from NMP; if the cleaning reagent is deionized water and / or anhydrous ethanol; and if the drying temperature is too low, the cleaning liquid is difficult to remove completely, while if the temperature is too high, it has an adverse effect on the drying equipment.

[0014] Preferably, the titanium source in step (2) is one or a combination of titanium dioxide, titanic acid, titanium sulfate, and titanium tetrachloride.

[0015] Preferably, the lithium source is a mixture of lithium carbonate and lithium hydroxide, wherein the molar ratio of lithium carbonate to lithium hydroxide is (0.05:0.95) to (0.20:0.80). If the molar ratio of lithium carbonate to lithium hydroxide is too high or too low, it is not conducive to the formation of a low-melting-point eutectic salt; non-eutectic salts cannot lower the melting point, and the regeneration effect deteriorates at the same temperature and calcination time.

[0016] Preferably, the molar ratio of lithium:nickel+cobalt+manganese:titanium in the composite material in step (2) is (1.05+2x):1:(x+0.01), where x = 0.01~0.04. If the amount of lithium added is too low, the time required for lithium replenishment and regeneration will be longer; if the amount of lithium added is too high, the excess residual lithium on the surface will affect the electrochemical performance of the lithium nickel cobalt manganese oxide material; if the amount of titanium added is too high, the charge-discharge specific capacity of the regenerated lithium nickel cobalt manganese oxide material will be low; if the amount of titanium added is too low, the cycle stability of the regenerated lithium nickel cobalt manganese oxide material will be poor. Excessive mixed lithium salt can shorten the lithium replenishment and repair time. Then, an excess titanium source is introduced to react with the remaining mixed lithium salt after lithium replenishment and repair on the surface of the lithium nickel cobalt manganese oxide material to generate a uniform lithium metatitanate (Li2TiO3) coating layer. The unreacted 1% excess tetravalent titanium ions penetrate into the lithium nickel cobalt manganese oxide to achieve doping and improve the ionic conductivity of the material.

[0017] Preferably, the two-stage sintering in step (3) is as follows: first, the temperature is raised to 428-460°C at a rate of 1-10°C / min and sintered for 8-10 hours, and then the temperature is raised to 680-720°C at a rate of 1-10°C / min and sintered for 1-3 hours; sintering is carried out in an air atmosphere and / or an oxygen atmosphere.

[0018] Preferably, the first stage of sintering at 428-460℃ utilizes the principle of low eutectic salts, lowering the melting point of the mixed lithium salt of lithium carbonate and lithium hydroxide, allowing the eutectic lithium salt to melt into a liquid state at a lower temperature. This more complete solid-liquid reaction interface repairs defects such as the loss of active lithium ions in waste nickel-cobalt-manganese oxide. The second stage of high-temperature sintering at 680-720℃ further enhances the hypercrystallization of nickel-cobalt-manganese oxide. Simultaneously, the excess titanium source reacts with the remaining lithium salt after lithium replenishment repair on the surface of the nickel-cobalt-manganese oxide material to generate a uniform lithium metatitanate (Li2TiO3) coating layer. The unreacted 1% excess tetravalent titanium ions penetrate into the nickel-cobalt-manganese oxide to achieve doping, improving the material's ionic conductivity.

[0019] Preferably, the titanium layer constructs a repair synergistic low eutectic salt regeneration waste nickel cobalt manganese oxide cathode material with a core-shell coating structure, the coating layer being a lithium titanate layer, and the core being titanium-doped nickel cobalt manganese oxide.

[0020] Preferably, the molar content of the lithium metatitanate coating layer accounts for 1-4% of the recycled waste lithium nickel cobalt manganese oxide cathode material, and the molar amount of titanium doping in the titanium-doped lithium nickel cobalt manganese oxide is less than 1% of the molar content of the lithium nickel cobalt manganese oxide. Recycled waste lithium nickel cobalt manganese oxide cathode material.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The titanium layer-constructed repair synergistic low-melting-point eutectic salt regeneration of waste lithium nickel cobalt manganese oxide cathode material prepared by the present invention is based on the principle of low-melting-point eutectic salt. Lithium carbonate and lithium hydroxide are fully mixed to prepare a low-melting-point eutectic salt, which is melted into a liquid state at a lower temperature, providing a more sufficient solid-liquid reaction interface. This allows for more efficient lithium replenishment and repair of waste lithium nickel cobalt manganese oxide cathode material, eliminating defects such as loss of active lithium ions. Subsequently, a short-time high-temperature calcination is used to further improve the crystallinity of the material. The regenerated material has uniform doping and coating, excellent rate performance, and greatly improved charge-discharge capacity and cycle stability.

[0023] 2. The titanium layer-constructed repair synergistic low eutectic salt regenerated waste lithium nickel cobalt manganese oxide cathode material prepared in this invention was assembled into a battery. Within a voltage range of 2.7–4.3V, at 1C (current density 1C = 180mA / g), the discharge specific capacity reached as high as 148.8mAh / g. After 100 cycles, the discharge specific capacity was still 137.5mAh / g, with a capacity retention rate of ≥92.4%. This indicates that during the charge and discharge process, the lithium metatitanate coating layer reduces side reactions and thus has good cycle performance. At high rates of 5C and 10C, the discharge specific capacity reached 131.2mAh / g and 114mAh / g, respectively. This indicates that the incorporation of tetravalent titanium ions improves the ionic conductivity of the regenerated lithium nickel cobalt manganese oxide cathode material, thereby improving the rate performance at high current densities.

[0024] 3. The method of the present invention shortens the lithium replenishment repair time by mixing waste lithium nickel cobalt manganese oxide cathode material with an excess of low-melting-point eutectic salt. An excess titanium source is introduced to react with the mixed lithium salt remaining after lithium replenishment repair on the surface of the lithium nickel cobalt manganese oxide material to generate a uniform lithium metatitanate (Li2TiO3) coating layer. At high temperature, 1% excess tetravalent titanium ions that have not reacted penetrate into the lithium nickel cobalt manganese oxide to achieve doping. The defects of active lithium ion loss in the recycled lithium nickel cobalt manganese oxide cathode material are repaired, and the reversible capacity is greatly improved. The lithium metatitanate coating layer can reduce the contact between lithium nickel cobalt manganese oxide and electrolyte during charging and discharging and the resulting side reactions. The incorporation of unreacted excess tetravalent titanium ions further improves the ionic conductivity of the recycled waste lithium nickel cobalt manganese oxide cathode material, thereby improving the rate performance at high current density.

[0025] 4. The method of the present invention has a wide range of raw material sources, is simple to operate, has low cost, low reaction temperature, short cycle, strong controllability, good repeatability, wide applicability, and is suitable for industrial production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is an XRD comparison image of the titanium layer-constructed repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 1 of the present invention and the waste nickel cobalt manganese oxide material.

[0028] Figure 2 The image shows the SEM image and titanium element distribution mapping of the titanium layer construction repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 1 of this invention.

[0029] Figure 3 This is a comparison of the Ni 2p3 / 2 characteristic peaks of the titanium layer-constructed repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 1 of the present invention;

[0030] Figure 4 This is a comparison chart of the cycle performance of the titanium layer construction repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 1 of the present invention and the waste nickel cobalt manganese oxide material.

[0031] Figure 5 This is a comparison chart of the rate performance of the titanium layer construction repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 1 of the present invention and the waste nickel cobalt manganese oxide material.

[0032] Figure 6 This is a comparison chart of the cycle performance of the titanium layer construction repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 2 of the present invention and the waste nickel cobalt manganese oxide material.

[0033] Figure 7 This is a comparison chart of the cycle performance of the titanium layer construction repair synergistic low eutectic salt regenerated waste nickel cobalt manganese oxide cathode material obtained in Example 3 of the present invention and the waste nickel cobalt manganese oxide material. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1:

[0038] A method for preparing a titanium layer-constructed repair synergistic low-eutectic salt recycled waste nickel-cobalt-manganese lithium oxide cathode material includes the following steps:

[0039] (1) Discharge and disassemble retired nickel cobalt manganese lithium oxide batteries to obtain positive electrode sheets. Immerse the positive electrode sheets in N-methylpyrrolidone (NMP) at 70 degrees Celsius and 50 kHz for 40 min, then centrifuge at 8000 r / min to separate solid and liquid. Clean the solid with anhydrous ethanol and dry it at 70°C to obtain waste nickel cobalt manganese lithium oxide positive electrode material.

[0040] (2) The waste nickel cobalt manganese lithium cathode material and titanium source were mechanically mixed. Lithium carbonate and lithium hydroxide were weighed in a molar ratio of 0.156:0.844 and manually ground and mixed evenly with an agate mortar to obtain mixture A. The molar ratio of lithium:(nickel+cobalt+manganese):titanium in mixture A was (1.05+0.06):1:(0.03+0.01).

[0041] (3) Material A is calcined at 428°C for 9 hours in an oxygen atmosphere and then calcined at 700°C for 2 hours. After cooling, the titanium layer construction repair synergistic low eutectic salt regeneration waste nickel cobalt manganese lithium cathode material is obtained.

[0042] This embodiment yields a core-shell structure lithium metatitanate coated with titanium-doped recycled lithium nickel cobalt manganese oxide cathode material, wherein the molar content of the lithium metatitanate coating layer accounts for 3% of the recycled lithium nickel cobalt manganese oxide cathode material; and the titanium doping amount is 1% of the molar content of lithium nickel cobalt manganese oxide.

[0043] Test the sample, such as Figure 1 As shown, the diffraction peaks of the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in the embodiments of the present invention are sharp, the surface crystallinity is good, and the diffraction peaks of lithium metatitanate can be observed, confirming that there is a lithium metatitanate coating layer on the surface of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0044] like Figure 2 As shown, the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in this embodiment of the invention has complete particles and is regularly spherical. The titanium element mapping diagram shows that the titanium element is uniformly distributed in the structure of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0045] like Figure 3 As shown, the Ni content in the recycled waste nickel-cobalt-manganese lithium oxide cathode material obtained in this embodiment of the invention is... 2+ The characteristic peaks of Ni are significantly enhanced compared to those of waste materials. 3+ The peak area decreased significantly. This demonstrates that lithium replenishment with molten lithium salts can efficiently eliminate defects caused by changes in elemental valence states in waste nickel-cobalt-manganese lithium oxide.

[0046] Battery assembly: Weigh 0.40g of the repaired and regenerated lithium nickel cobalt manganese oxide material obtained in the embodiment of the present invention, add 0.05g of acetylene black as a conductive agent and 0.05g of N-methylpyrrolidone as a binder, mix evenly and coat it on copper foil to form a positive electrode sheet. In a vacuum glove box, use a lithium metal sheet as the negative electrode, a lithium battery separator as the separator, and 1mol / L LiPF6 / EC:DMC (volume ratio 1:1) as the electrolyte to assemble a CR2025 coin cell.

[0047] Depend on Figure 4 It can be seen that within the voltage range of 2.7 to 4.3V, at 1C (current density 1C = 180mA / g), the discharge specific capacity is as high as 148.8mAh / g, and after 100 cycles, the discharge specific capacity is still 137.5mAh / g, with a capacity retention rate of ≥92.4%. This indicates that during the charge and discharge process, the lithium metatitanate coating reduces side reactions and thus has good cycle performance.

[0048] Depend on Figure 5 It can be seen that at high rates of 5C and 10C, the discharge specific capacity reaches 131.2mAh / g and 114mAh / g, respectively, indicating that the incorporation of tetravalent titanium ions improves the ionic conductivity of the recycled nickel cobalt manganese oxide cathode material, thereby improving the rate performance at high current densities.

[0049] Example 2:

[0050] A method for preparing a titanium layer-constructed repair synergistic low-eutectic salt recycled waste nickel-cobalt-manganese lithium oxide cathode material includes the following steps:

[0051] (1) Discharge and disassemble retired nickel cobalt manganese lithium oxide batteries to obtain positive electrode sheets. Immerse the positive electrode sheets in N-methylpyrrolidone (NMP) at 60 degrees Celsius and 30 kHz for 30 min, then centrifuge at 2000 r / min to separate solid and liquid. Clean the solid with anhydrous ethanol and dry it at 60°C to obtain waste nickel cobalt manganese lithium oxide positive electrode material.

[0052] (2) The waste lithium nickel cobalt manganese oxide cathode material and the titanium source were thoroughly mixed by manual grinding. Lithium carbonate and lithium hydroxide were weighed out separately with a molar ratio of 0.05:0.95 and thoroughly mixed by mechanical stirring to obtain mixture A. The molar ratio of lithium:(nickel+cobalt+manganese):titanium in mixture A was (1.05+0.02):1:(0.01+0.01).

[0053] (3) After calcining material C at 460°C for 10 hours in an oxygen atmosphere, the temperature is raised to 720°C and calcined for 3 hours. After cooling, the recycled waste nickel cobalt manganese oxide cathode material for lithium replenishment and repair is obtained.

[0054] This embodiment yields a core-shell structure lithium metatitanate coated with titanium-doped recycled lithium nickel cobalt manganese oxide cathode material, wherein the molar content of the lithium metatitanate coating layer accounts for 1% of the recycled lithium nickel cobalt manganese oxide cathode material; and the titanium doping amount is 1% of the molar content of lithium nickel cobalt manganese oxide.

[0055] Upon testing, the diffraction peaks of the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in the embodiments of the present invention are sharp, the surface crystallinity is good, and the diffraction peaks of lithium metatitanate can be observed, confirming that there is a lithium metatitanate coating layer on the surface of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0056] Upon testing, the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in this embodiment of the invention has intact particles and is regularly spherical. The titanium element mapping diagram shows that the titanium element is uniformly distributed in the structure of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0057] Testing revealed that the Ni content in the recycled waste nickel-cobalt-manganese lithium cathode material obtained in this embodiment of the invention was [missing information]. 2+ The characteristic peaks of Ni are significantly enhanced compared to those of waste materials. 3+ The peak area decreased significantly. This demonstrates that lithium replenishment with molten lithium salts can efficiently eliminate defects caused by changes in elemental valence states in waste nickel-cobalt-manganese lithium oxide.

[0058] Battery assembly: Weigh 0.40g of the repaired and regenerated lithium nickel cobalt manganese oxide material obtained in the embodiment of the present invention, add 0.05g of acetylene black as a conductive agent and 0.05g of N-methylpyrrolidone as a binder, mix evenly and coat it on copper foil to form a positive electrode sheet. In a vacuum glove box, use a lithium metal sheet as the negative electrode, a lithium battery separator as the separator, and 1mol / L LiPF6 / EC:DMC (volume ratio 1:1) as the electrolyte to assemble a CR2025 coin cell.

[0059] Depend on Figure 6 It can be seen that within the voltage range of 2.7 to 4.3V, at 1C (current density 1C = 180mA / g), the discharge specific capacity is as high as 150.3mAh / g, and after 100 cycles, the discharge specific capacity is still 133.4mAh / g, with a capacity retention rate of ≥88.7%. This indicates that during the charge and discharge process, the lithium metatitanate coating reduces side reactions and thus has good cycle performance.

[0060] Testing revealed that the discharge specific capacity reached 129.3 mAh / g and 109.8 mAh / g at high rates of 5C and 10C, respectively. This indicates that the incorporation of tetravalent titanium ions improves the ionic conductivity of the recycled nickel cobalt manganese oxide cathode material, thereby enhancing its rate performance at high current densities.

[0061] Example 3:

[0062] A method for preparing a titanium layer-constructed repair synergistic low-eutectic salt recycled waste nickel-cobalt-manganese lithium oxide cathode material includes the following steps:

[0063] (1) Discharge and disassemble retired nickel-cobalt-manganese lithium oxide batteries to obtain positive electrode sheets. Immerse the positive electrode sheets in N-methylpyrrolidone (NMP) at 80 degrees Celsius and sonicate at 60 kHz for 50 min, then centrifuge at 10000 r / min to separate solid and liquid. Wash the solid with deionized water and dry it at 110°C to obtain waste nickel-cobalt-manganese lithium oxide positive electrode material.

[0064] (2) The waste nickel cobalt manganese lithium cathode material and the titanium source were thoroughly mixed by manual grinding to obtain material A; lithium carbonate and lithium hydroxide were weighed in a molar ratio of 0.20:0.80 and thoroughly mixed by manual grinding with an agate mortar to obtain mixture A; the molar ratio of lithium:(nickel+cobalt+manganese):titanium in mixture C was (1.05+0.08):1:(0.04+0.01);

[0065] (3) Material A is calcined at 458°C for 8 hours in an oxygen atmosphere and then calcined at 680°C for 1 hour. After cooling, the recycled waste nickel cobalt manganese oxide cathode material for lithium replenishment and repair is obtained.

[0066] This embodiment yields a core-shell structure lithium metatitanate coated with titanium-doped recycled lithium nickel cobalt manganese oxide cathode material, wherein the molar content of the lithium metatitanate coating layer accounts for 4% of the recycled lithium nickel cobalt manganese oxide cathode material; and the titanium doping amount is 1% of the molar content of lithium nickel cobalt manganese oxide.

[0067] Upon testing, the diffraction peaks of the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in the embodiments of the present invention are sharp, the surface crystallinity is good, and the diffraction peaks of lithium metatitanate can be observed, confirming that there is a lithium metatitanate coating layer on the surface of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0068] Upon testing, the recycled waste lithium nickel cobalt manganese oxide cathode material obtained in this embodiment of the invention has intact particles and is regularly spherical. The titanium element mapping diagram shows that the titanium element is uniformly distributed in the structure of the recycled waste lithium nickel cobalt manganese oxide cathode material.

[0069] Testing revealed that the Ni content in the recycled waste nickel-cobalt-manganese lithium cathode material obtained in this embodiment of the invention was [missing information]. 2+ The characteristic peaks of Ni are significantly enhanced compared to those of waste materials. 3+ The peak area decreased significantly. This demonstrates that lithium replenishment with molten lithium salts can efficiently eliminate defects caused by changes in elemental valence states in waste nickel-cobalt-manganese lithium oxide.

[0070] Battery assembly: Weigh 0.40g of the repaired and regenerated lithium nickel cobalt manganese oxide material obtained in the embodiment of the present invention, add 0.05g of acetylene black as a conductive agent and 0.05g of N-methylpyrrolidone as a binder, mix evenly and coat it on copper foil to form a positive electrode sheet. In a vacuum glove box, use a lithium metal sheet as the negative electrode, a lithium battery separator as the separator, and 1mol / L LiPF6 / EC:DMC (volume ratio 1:1) as the electrolyte to assemble a CR2025 coin cell.

[0071] Depend on Figure 7 It can be seen that within the voltage range of 2.7 to 4.3V, at 1C (current density 1C = 180mA / g), the discharge specific capacity is as high as 143.1mAh / g, and after 100 cycles, the discharge specific capacity is still 132.7mAh / g, with a capacity retention rate of ≥92.7%. This indicates that during the charge and discharge process, the lithium metatitanate coating reduces side reactions and thus has good cycle performance.

[0072] Testing revealed that the discharge specific capacity reached 127.1 mAh / g and 110.6 mAh / g at high rates of 5C and 10C, respectively. This indicates that the incorporation of tetravalent titanium ions improves the ionic conductivity of the recycled nickel cobalt manganese oxide cathode material, thereby enhancing its rate performance at high current densities.

[0073] The recycled waste nickel-cobalt-manganese lithium oxide cathode material of the present invention has uniform doping and coating, excellent rate performance, and greatly improved charge-discharge capacity and cycle stability.

Claims

1. A titanium layer-constructed repair and synergistic low-eutectic salt regeneration method for waste nickel-cobalt-manganese lithium oxide cathode materials, characterized in that, The titanium-constructed repair synergistic low eutectic salt regenerated waste nickel-cobalt-manganese lithium oxide cathode material has a core-shell coating structure. The coating layer is a lithium metatitanate layer, and the core is titanium-doped lithium nickel-cobalt-manganese oxide. The molar content of the lithium metatitanate coating layer in the regenerated waste nickel-cobalt-manganese lithium oxide cathode material accounts for 1-4% of the total molar content of the regenerated waste nickel-cobalt-manganese lithium oxide cathode material. The molar amount of titanium doping in the titanium-doped lithium nickel-cobalt-manganese oxide is less than 1% of the total molar content of the lithium nickel-cobalt-manganese oxide. The preparation method includes the following steps: (1) After cutting the electrode sheet, place it in N-methylpyrrolidone solution, dissolve it by ultrasonication, filter, wash, dry and sieve to obtain waste nickel cobalt manganese oxide positive electrode material; (2) The waste nickel cobalt manganese oxide lithium cathode material obtained in step (1) is mixed evenly with the titanium source, and then the lithium source is added and mixed evenly to obtain the composite material; wherein the lithium source is a mixture of lithium carbonate and lithium hydroxide, and the molar ratio of lithium carbonate to lithium hydroxide is (0.05:0.95)~(0.20:0.80); (3) The composite material obtained in step (2) is sintered in two stages under an oxidizing atmosphere and cooled to room temperature to obtain a recycled waste nickel cobalt manganese oxide cathode material for lithium replenishment and repair; wherein, the two-stage sintering is as follows: first, the temperature is raised to 428~460℃ at a rate of 1~10 ℃ / min and sintered for 8~10 h, and then the temperature is raised to 680~720℃ at a rate of 1~10 ℃ / min and sintered for 1~3 h; sintering is carried out in an air atmosphere and / or an oxygen atmosphere.

2. The titanium layer construction for repairing and synergistically regenerating waste nickel-cobalt-manganese lithium oxide cathode material according to claim 1, characterized in that, The electrode sheet mentioned in step (1) is a positive electrode sheet obtained by discharging and dismantling waste nickel-cobalt-manganese lithium batteries.

3. The titanium layer construction for repairing synergistic low-eutectic salt regeneration of waste nickel-cobalt-manganese lithium cathode material according to claim 1, characterized in that, The ultrasonic dissolution process conditions in step (1) are as follows: immerse the positive electrode in N-methylpyrrolidone and sonicate at 30-60 kHz for 30-50 min at 60-80℃; the cleaning reagent is deionized water and / or anhydrous ethanol; and the drying temperature is 60-110℃.

4. The titanium layer construction for repairing synergistic low-eutectic salt regeneration of waste nickel-cobalt-manganese lithium cathode material according to claim 1, characterized in that, The titanium source mentioned in step (2) is one or a combination of several of titanium dioxide, titanic acid, titanium sulfate, and titanium tetrachloride.

5. The titanium layer construction for repairing synergistic low-eutectic salt regeneration of waste nickel-cobalt-manganese lithium cathode material according to claim 1, characterized in that, In step (2), the molar ratio of lithium:nickel+cobalt+manganese:titanium in the composite material is (1.05+2x)∶1∶(x+0.01), where x=0.01~0.04.

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