Regeneration method and application of waste ternary positive electrode material

Abstract

The invention provides a regeneration method and application of a waste ternary positive electrode material. Comprising the following steps that S1, the waste single crystal and polycrystal mixed ternary positive electrode material and an oxidizing agent are mixed and react in an alkaline aqueous solution system with the pH being 12.5-14 and the temperature being 25-50 DEG C, an oxide precursor is obtained, the surface of the oxide precursor is of a layered NiOOH structure, the morphology is single crystal particles, and the surface of the oxide precursor is of a NiOOH structure; s2, adding a lithium source and doped metal salt into the alkaline system, and reacting to obtain a doped lithium-intercalated positive electrode material precursor; and S3, carrying out high-temperature annealing on the doped lithium-intercalated positive electrode material precursor to obtain the doped modified regenerated single crystal positive electrode material. According to the method, surface structure reconstruction and bulk phase lattice repair of the waste ternary positive electrode material are achieved under the mild condition, the technological process is simple, lithium supplementing and doping are uniform, and the obtained regenerated positive electrode material has good structural stability and electrochemical performance and is suitable for the field of recycling and regeneration of lithium ion battery positive electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery recycling technology, and particularly relates to a method and application for the regeneration of waste ternary cathode materials. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, high operating voltage, and long cycle life, have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage power stations. In recent years, driven by the rapid development of the new energy vehicle industry, the installed capacity of power lithium-ion batteries has continued to climb, and the market size has continued to expand. However, as early power batteries gradually enter their retirement cycle, the problem of processing and recycling spent lithium-ion batteries is becoming increasingly serious, urgently requiring the development of efficient, green, and economical recycling technologies.

[0003] In lithium-ion battery cathode material systems, nickel-cobalt-manganese ternary oxides (NCMs) have become the mainstream cathode material due to their combination of high specific capacity and relatively controllable cost. Among them, high-nickel ternary materials further improve energy density by increasing nickel content, but their cycle stability and thermal safety are relatively poor. During long-term charge-discharge or storage, these materials are prone to problems such as lithium loss, cation mixing, surface structure collapse, and accumulation of bulk lattice defects, leading to a significant degradation in electrochemical performance.

[0004] Currently, the following three technical routes are mainly used for the recycling and treatment of waste ternary cathode materials: (1) Pyrometallurgical method: Organic components are burned off by high-temperature smelting or incineration, and metal alloys are recovered. This method is simple, but energy consumption is extremely high, it is easy to generate toxic gases such as dioxins, and it cannot retain the original crystal structure of the cathode material, so it cannot be directly recycled. (2) Hydrometallurgical method: Strong acid is used in combination with reducing agent to completely leach out metal elements such as Ni, Co, Mn, and Li in the cathode material, and then the precursor and cathode material are resynthesized through extraction separation, co-precipitation and other steps. Although the metal recovery rate is high, the process is lengthy, reagent consumption is large, waste liquid treatment cost is high, and there is metal loss in multiple steps, which limits the overall economic efficiency and environmental friendliness. (3) Direct regeneration method: The aim is to restore the electrochemical performance of waste cathode materials by lithium replenishment and structural repair without destroying the main layered structure of the material. This method has the advantages of short process, low energy consumption, and closed-loop utilization of materials, and is regarded as the most promising green recycling path. However, existing direct regeneration technologies still have significant shortcomings: they rely heavily on high-temperature solid-state reactions for lithium replenishment, which consumes a lot of energy and is prone to particle sintering or phase transformation; the doping and modifying elements are difficult to embed uniformly into the crystal lattice, resulting in incomplete structural repair; there is a lack of effective activation methods for the surface degradation layer, and the lithium compensation and lattice reconstruction lack synergy, resulting in the capacity recovery rate and cycle stability of the regenerated materials being lower than those of the original materials.

[0005] In summary, current technologies have not yet solved the key challenge of efficiently activating the surface of spent ternary cathode materials under mild conditions, simultaneously achieving lithium compensation and doping modification, and completing high-quality lattice reconstruction. Therefore, there is an urgent need to develop a direct regeneration method with mild process conditions, precise structural repair, full performance recovery, and industrial feasibility. Summary of the Invention

[0006] The present invention aims to develop a method for regenerating waste ternary cathode materials, which aims to overcome the problems of complex processing, uneven lithium replenishment, and incomplete structural repair in the existing waste ternary cathode material regeneration process.

[0007] To achieve the above objectives, the present invention provides a method for regenerating waste ternary cathode materials, comprising the following steps: S1. Waste ternary cathode material and oxidant are mixed and reacted in an alkaline system with pH 12.5~14 and temperature 25~50℃ to obtain an intermediate composed of primary particles; The surface of the primary particles has a layered NiOOH structure; The D50 of the primary particles is 0.5~1μm; The intermediate has the molecular formula Li. 1-a Ni b Co c Mn d O2, where 0 < a < 1, 0.3 ≤ b ≤ 0.9, 0.05 ≤ c ≤ 0.3, 0.05 ≤ d ≤ 0.3, b + c + d = 1; S2. Add a lithium source and a doped metal salt to the alkaline system to react and obtain a doped lithium-intercalated cathode material precursor; S3. The obtained doped lithium-intercalated cathode material precursor is annealed at high temperature to obtain a regenerated single-crystal cathode material with a doped and modified D50 of 2~5μm.

[0008] The waste ternary cathode material is a mixture containing single-crystal particles and polycrystalline secondary particles.

[0009] In step S1, the waste ternary cathode material is reacted with an oxidant in an alkaline aqueous solution system with a pH of 12.5–14 and a temperature of 25–50°C. This selective oxidation of the degraded surface regions, while maintaining the stability of the main layered structure of the material, transforms the surface Ni from a low valence state to a high valence state and reconstructs a layered NiOOH structure. This NiOOH layer not only repairs the surface structural defects of the waste cathode but also significantly improves the chemical activity and ion accessibility of the material surface. Simultaneously, it avoids the problems of lattice collapse and metal dissolution under strong acid or high temperature conditions, allowing the intermediate bulk phase to maintain a highly ordered layered structure. In step S2, a lithium source and a doped metal salt are simultaneously introduced into the same alkaline reaction system. Utilizing the surface reconstruction structure and activation channels formed in step S1, lithium ions preferentially compensate for lithium vacancies in the precursor, while simultaneously promoting the uniform embedding of dopant elements into the layered lattice. This mechanistically suppresses cation mixing and enhances the stability of the layered structure, achieving a synergistic effect of lithium replenishment and doping. In step S3, the lithium-intercalated cathode material precursor is subjected to high-temperature annealing to further promote the orderly arrangement of lithium ions and dopant elements in the crystal lattice, eliminate residual defects in the precursor, and complete the crystal lattice reconstruction and structural shaping, thereby obtaining a doped modified regenerated cathode material with stable structure and good electrochemical performance recovery.

[0010] Through the synergistic effect of the above steps, this invention achieves surface reconstruction, bulk repair, and performance recovery of waste ternary cathode materials without the need to re-prepare hydroxide precursors. The process conditions are mild, the structural repair mechanism is clear, and the cycle stability and rate performance of the recycled materials are significantly improved, demonstrating good industrial application value.

[0011] According to an embodiment of the present invention, the oxidant includes at least one selected from persulfate, hydrogen peroxide, oxygen, ozone, potassium permanganate, hypochlorite, chlorate, and perchlorate.

[0012] According to an embodiment of the present invention, the D50 of the primary particles is 0.5~1μm, specifically, the D50 of the primary particles is 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 1.0μm.

[0013] According to an embodiment of the present invention, the D50 of the obtained doped and modified regenerated single-crystal cathode material is 2~5μm, specifically, the D50 of the primary particles is 3μm, 3.5μm, 4μm or 4.6μm.

[0014] According to an embodiment of the present invention, the oxidant includes persulfate.

[0015] Under conditions of pH 12.5–14, persulfate generates hydroxyl radicals. The redox potential of hydroxyl radicals is 2.8 V, which is higher than that of Ni. 2+To Ni 3+ The redox potential (2.5 V) is therefore relevant to the anti-Ni² sites in the LiO6 octahedron of the waste ternary cathode. + (Higher activity) is also oxidized to Ni³ + Due to the radius change and the charge balance requirement, it reverts to the TMO6 octahedron, resulting in c-axis elongation and lattice distortion. This increases the internal stress of the secondary particles, causing significant lattice distortion and anisotropic internal stress accumulation. When the stress exceeds the grain boundary bonding strength within the secondary particles, it causes the originally densely sintered micron-sized secondary particles to break along the grain boundaries, eventually disaggregating into primary particles (primary particles) with uniform particle size and good dispersion.

[0016] According to an embodiment of the present invention, the molar ratio of the waste ternary cathode to the oxidant is 1:0.5 to 2.5.

[0017] Under the above conditions, selective and mild oxidation of waste cathode materials is achieved under alkaline low-temperature conditions. Within this ratio range, the oxidant can effectively promote the formation of NiOOH layered structure on the surface Ni, restore surface activity and open lithium-ion diffusion channels, without causing excessive oxidation, dissolution or structural damage to the main crystal lattice due to excessive oxidant dosage, thus ensuring that the bulk phase of the material still maintains a highly ordered layered structure.

[0018] According to an embodiment of the present invention, step S1 further includes adding Na2CO3, wherein the amount of Na2CO3 added is 0.01~0.1mol / L.

[0019] According to an embodiment of the present invention, in step S1, the mixing reaction time is 1 to 48 hours, and the solid-liquid mass-volume ratio of the waste ternary cathode material to the alkaline aqueous solution is 1 to 10 g / mL.

[0020] According to an embodiment of the present invention, in step S1, the mixing reaction time is 6 to 24 hours, and the solid-liquid mass-volume ratio of the waste ternary cathode material to the alkaline aqueous solution is 8 to 10 g / mL.

[0021] According to an embodiment of the present invention, in step S1, the pH of the system is 13.

[0022] Within the above reaction time range, the oxidant can gradually act on the surface of the waste ternary cathode material under alkaline low temperature conditions, so that the surface degradation area can fully complete the transformation from low-valence Ni to high-valence Ni, and stably reconstruct to form a layered NiOOH structure. By controlling the solid-liquid mass-volume ratio at 1–10 g / mL, the waste ternary cathode material can maintain a good dispersion state in the alkaline aqueous solution system, enhance the uniformity of contact between the oxidant and the particle surface, avoid insufficient local oxidation caused by an excessively high solid-liquid ratio, or ineffective oxidant consumption and increased side reactions caused by an excessively low solid-liquid ratio, thereby facilitating the formation of a uniform surface NiOOH reconstruction layer.

[0023] The synergistic control of the reaction time and solid-liquid ratio allows the intermediate obtained in step S1 to achieve a balance in terms of surface reconstruction degree, bulk integrity and structural uniformity. This provides a stable and controllable structural basis for lithium-ion compensation and uniform embedding of doping elements in the subsequent step S2, further improving the structural stability and electrochemical performance of the regenerated cathode material.

[0024] According to an embodiment of the present invention, in step S2, the reaction time is 1 to 48 hours, the reaction temperature is 80 to 200°C, and the reaction pressure is 0.1 to 2.0 MPa.

[0025] Under the above conditions, on the one hand, the temperature range of 80 to 200°C can significantly improve the migration rate of lithium ions and doped ions, overcome the diffusion resistance inside the waste cathode material, and make them not only stay on the particle surface, but also gradually penetrate into the particle interior; on the other hand, the reaction pressure of 0.1 to 2.0 MPa is conducive to maintaining the stability of the solution phase and the ion transport environment, and further promotes the uniform embedding of ions in the layered structure.

[0026] By controlling the reaction time within 1 to 48 hours, lithium vacancies can be fully compensated, while avoiding particle agglomeration, structural distortion, or side reactions that may occur under prolonged high temperature and high pressure conditions, thus achieving a balance between lithium replenishment efficiency and structural stability.

[0027] The coordinated setting of the above reaction time, temperature and pressure parameters makes the lithium-intercalated cathode material precursor obtained in step S2 significantly better than the existing direct lithium replenishment or high-temperature solid-state doping methods in terms of lithium distribution uniformity, doping element stability and layered structure integrity. This lays a good structural foundation for the high-temperature annealing lattice reconstruction in the subsequent step S3, thereby improving the cycle performance and rate performance of the regenerated cathode material.

[0028] According to an embodiment of the present invention, the lithium source comprises a soluble lithium salt; The soluble lithium salt includes at least one of lithium acetate, lithium sulfate, lithium nitrate, and lithium hydroxide.

[0029] According to an embodiment of the present invention, the doped metal salt includes at least one of Na, Mg, K, Al or Ca.

[0030] According to an embodiment of the present invention, the molar ratio of the dopant element in the doped metal salt to the total metal elements in the intermediate is 0.001 to 0.05:1.

[0031] According to an embodiment of the present invention, the molar ratio of the dopant element in the doped metal salt to the total metal elements in the intermediate is 0.006:1.

[0032] Under the above conditions, doping elements can preferentially enter the defect sites of lithium layers or transition metal layers in the intermediate layered structure, thereby forming a stable local coordination environment, suppressing lithium vacancy-induced cation mixing, and enhancing the structural stability of the layered structure during subsequent high-temperature annealing. At the same time, the lower doping ratio avoids the problems of lattice distortion, phase separation, or shielding of electrochemical active sites caused by excessive doping elements, thus ensuring the integrity of the main active structure from a mechanistic perspective.

[0033] According to an embodiment of the present invention, in step S3, the temperature of the high-temperature annealing is 650-900°C; the time of the high-temperature annealing is 8-20 hours; and the atmosphere of the high-temperature annealing is air or pure oxygen.

[0034] The direct oxidation regeneration method for waste ternary cathode materials described in this invention has the following significant advantages compared to existing recycling technologies: (1) Simplified process flow to achieve closed-loop material regeneration. This invention uses waste ternary cathode materials (such as NCM622, NCM811, etc.) from retired lithium-ion batteries as direct regeneration raw materials. It does not require complex hydrometallurgical steps such as acid leaching, metal separation, and co-precipitation, nor does it require the resynthesis of hydroxide or carbonate precursors. This significantly shortens the process chain, reduces reagent consumption and equipment investment, and significantly improves resource utilization efficiency, which is in line with the development requirements of green, low-carbon and circular economy.

[0035] (2) Achieving precise surface reconstruction and bulk structure protection under mild conditions. Through controlled oxidation treatment in a strongly alkaline (pH = 12.5~14) and low-temperature (<50℃) environment, the Ni enriched on the material surface is selectively reconstructed. 2+ In-situ conversion into a layered NiOOH active phase effectively repairs the surface degradation layer caused by lithium loss. Simultaneously, it causes the originally dense sintered micron-sized secondary particles to fragment along the grain boundaries, eventually deaggregating into primary particles with uniform particle size and good dispersion, providing a prerequisite for subsequent regeneration into single-crystal particles. In addition, this process avoids the destruction of the bulk layered lattice by high temperature or strong acid environment, maintaining the high orderliness of the main structure and providing a good structural foundation for subsequent lithium intercalation.

[0036] (3) Synergistic optimization of crystal chemical environment through simultaneous lithium replenishment and doping. Under hydrothermal or solvothermal conditions, the lithium source and dopant elements can be simultaneously and uniformly embedded in the lattice, which on the one hand efficiently compensates for lithium vacancies, and on the other hand suppresses Ni through hetero-ion doping. 2+ Migration into the Li layer significantly reduces cation mixing. This synergistic mechanism effectively enhances the structural stability of the recycled material, enabling it to exhibit excellent capacity retention and rate performance under high-voltage cycling and high-rate charge-discharge conditions.

[0037] (4) The overall process is green, low-consumption, and scalable. This invention avoids the use of highly corrosive acids, organic solvents, or high-energy-consuming high-temperature solid-phase reactions. The main reaction steps are completed at medium and low temperatures and at atmospheric to medium pressures, with energy consumption significantly lower than that of traditional pyrometallurgical or wet recycling processes. The electrochemical performance (such as first-cycle discharge capacity and cycle stability) of the resulting recycled cathode material can be restored to more than 95% of that of the original material, and some indicators are even better than those of commercial new products. It has good batch consistency and industrial scale-up potential, and is suitable for the high-efficiency resource utilization needs in the context of the large-scale retirement of power batteries.

[0038] The present invention also proposes an application of the regenerated ternary cathode material prepared by the method in lithium-ion batteries. Attached Figure Description

[0039] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0040] Figure 1 The image shows the TEM spectrum of the waste NCM811 ternary cathode material in Example 5.

[0041] Figure 2 The image shows the TEM spectrum of the oxide precursor prepared in Example 5.

[0042] Figure 3 The images show the SEM images of the waste NCM811 ternary cathode material, the oxide precursor, and the regenerated NCM811 ternary cathode material in Example 5.

[0043] Figure 4 The cycling performance of the waste NCM622 and recycled NCM622 ternary cathode materials in Example 6 is shown.

[0044] Figure 5The images show the SEM images of the waste NCM622 ternary cathode material, the oxide precursor, and the regenerated NCM622 ternary cathode material in Example 6.

[0045] Figure 6 The cycling performance of the waste NCM622 and recycled NCM622 ternary cathode materials in Example 6 is shown.

[0046] Figure 7 The images show the SEM images of the waste NCM523 ternary cathode material, the oxide precursor, and the regenerated NCM523 ternary cathode material in Example 7.

[0047] Figure 8 The cycling performance of the waste NCM523 and recycled NCM523 ternary cathode materials in Example 7 is shown.

[0048] Figure 9 The images show the SEM spectra of the waste ternary cathode material in Comparative Example 1, the SEM spectra of the oxide precursor, and the SEM spectra of the regenerated NCM622 ternary cathode material.

[0049] Figure 10 The images show the SEM spectra of the waste NCM622 ternary cathode material in Comparative Example 2, the SEM spectra of the oxide precursor, and the SEM spectra of the regenerated NCM622 ternary cathode material.

[0050] Figure 11 The images show the SEM spectra of the waste NCM622 ternary cathode material in Comparative Example 3, the SEM spectra of the oxide precursor, and the SEM spectra of the regenerated NCM622 ternary cathode material.

[0051] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0054] Example 1 This embodiment provides a method for regenerating waste ternary cathode materials, including the following steps: S1. Selected retired NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O2) ternary cathode material, sodium persulfate (Na2S2O8) is added as an oxidant to a NaOH solution with pH=13, with a solid-liquid ratio of 1:5 g / mL (the solid is decommissioned NCM811, and the liquid is NaOH with pH=13 and sodium persulfate dissolved in it), waste ternary cathode material (LiNi 0.8 Co 0.1 Mn 0.1 The molar ratio of O2 to the oxidant is 1:2. The reaction is carried out at 40°C for 12 hours to obtain an oxide precursor (an intermediate composed of primary particles) with a NiOOH layered structure on its surface. S2. Without separating the oxidation intermediate obtained in step S1, lithium hydroxide (LiOH) is added to the same reaction system as a lithium source, and aluminum nitrate and magnesium nitrate are added as dopants; The ratio of the amount of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the waste cathode material is 2:1. The molar ratio of aluminum to the total transition metals was 0.005:1, and the molar ratio of magnesium to the total transition metals was also 0.005:1. That is, the doping amount of aluminum and magnesium was 0.5 mol% of the total transition metals, and the total doping molar ratio was 1 mol%. The mixture was sealed in a high-pressure reactor and hydrothermally reacted at 90℃ and 0.2 MPa for 10 hours. After the reaction, it was naturally cooled to room temperature, repeatedly centrifuged and washed with deionized water until the filtrate was neutral, and then vacuum dried at 80℃ for 12 hours to obtain the lithium intercalation doped intermediate. S3. The lithium-intercalated doped intermediate was annealed at 750°C in a pure oxygen atmosphere for 12 hours to obtain Al / Mg-doped regenerated NCM811 material.

[0055] Example 2 This embodiment provides a method for regenerating waste ternary cathode materials, including the following steps: S1. Selected retired NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 O2) ternary cathode material, hydrogen peroxide is added as an oxidant in NaOH solution with pH=13, solid-liquid ratio 1:5, temperature 40℃, reaction for 12h, to obtain an oxide precursor with NiOOH layered structure on the surface; S2. Lithium hydroxide (LiOH) and Al and Mg doped salts were added to the same system, making the molar ratio of lithium source to total metal 3:1 and the molar ratio of dopant 0.02:1. Reaction conditions: temperature 90℃, pressure 0.2 MPa, time 10 h. After washing and drying, the lithium-intercalated doped precursor was obtained. S3. The precursor was annealed at 800℃ in a pure oxygen atmosphere for 15 hours to obtain Al / Mg-doped regenerated NCM622 material.

[0056] Example 3 This embodiment provides a method for regenerating waste ternary cathode materials, including the following steps: S1. Select retired NCM523 (LiN) i0.5 Co 0.2 Mn 0.3 Ozone (O3) gas was bubbled into an alkaline solution at pH 13, with a solid-liquid ratio of 1:5 and a reaction temperature of 35℃ for 10 h. This yielded an oxide precursor with a NiOOH layered structure on its surface. S2. Lithium hydroxide (LiOH) and Al and Mg dopant salts were added to the same system, making the molar ratio of lithium source to total metal 2:1 and the doping molar ratio 0.01:1. Reaction conditions: temperature 90℃, pressure 0.2 MPa, time 10h. After washing and drying, the lithium-intercalated doped precursor was obtained. S3. The precursor was annealed at 850℃ in a pure oxygen atmosphere for 15 hours to obtain Al / Mg-doped regenerated NCM523 material.

[0057] Example 4 The difference between this embodiment and Embodiment 1 is that step S1 further includes the addition of Na2CO3, wherein the amount of Na2CO3 added is 0.05 mol / L, specifically: S1. Selected retired NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 The O2) ternary cathode material was prepared by adding sodium persulfate (Na2S2O8) as an oxidant to a NaOH solution with pH=13, with a solid-liquid ratio of 1:10 g / mL (the solid was decommissioned NCM811, and the liquid was NaOH solution with pH=13 and sodium persulfate dissolved in it), and the amount of Na2CO3 added was 0.05 mol / L. The temperature was 25℃, and the reaction was carried out for 12 h to obtain an oxide precursor with a NiOOH layered structure on the surface. The precursor morphology was single crystal particles. S2. Lithium hydroxide (LiOH) and Al and Mg doped salts were added to the same system, with the molar ratio of lithium source to total metal being 3:1, the molar ratio of Al doping being 0.003:1, and the molar ratio of Mg doping being 0.003:1. The reaction conditions were: temperature 120℃, pressure 0.5MPa, and time 12h. After washing and drying, the lithium intercalation doped precursor was obtained. S3. The precursor was annealed at 750℃ in a pure oxygen atmosphere for 12 hours to obtain Al / Mg-doped regenerated single crystal NCM811 material.

[0058] Under the above conditions, on the one hand, the pH of the system can be buffered, reducing the local high oxidation potential caused by the decomposition of persulfate; on the other hand, NiOOH can be generated layer by layer on the particle surface in a controlled manner. This is conducive to the formation of a continuous, dense and thin NiOOH layered structure, providing a more stable interface channel for subsequent lithium-ion intercalation and structural repair.

[0059] Example 5 This embodiment provides a method for regenerating waste ternary cathode materials, including the following steps: S1. Selected retired NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 The ternary cathode material (O2) was prepared by adding sodium persulfate (Na2S2O8) as an oxidant to a NaOH solution with pH=13, with a solid-liquid ratio of 1:10 g / mL (the solid was decommissioned NCM811, and the liquid was NaOH with pH=13 and sodium persulfate dissolved therein), at a temperature of 25℃ for 12 h, to obtain an oxide precursor with a NiOOH layered structure on the surface. The precursor morphology was single crystal particles. S2. Lithium hydroxide (LiOH) and Al and Mg doped salts were added to the same system, with the molar ratio of lithium source to total metal being 3:1, the molar ratio of Al doping being 0.003:1, and the molar ratio of Mg doping being 0.003:1. The reaction conditions were: temperature 120℃, pressure 0.5MPa, and time 12h. After washing and drying, the lithium intercalation doped precursor was obtained. S3. The precursor was annealed at 750℃ in a pure oxygen atmosphere for 12 hours to obtain Al / Mg-doped regenerated single crystal NCM811 material.

[0060] Figure 1 The transmission electron microscope (TEM) images of the waste NCM811 ternary cathode material in Example 5 are shown. The degradation structure on the surface of the waste material can be observed, including the rock salt phase caused by lithium loss. These features reflect the performance degradation of the material during long-term charge and discharge. Figure 2The transmission electron microscope (TEM) image of the oxide precursor prepared by step S1 in Example 5 is shown, in which the surface layer of the material is clearly reconstructed into a layered NiOOH structure. This structure repairs the surface defects of the waste material and improves the chemical activity and ion diffusion channel availability, while maintaining the orderliness of the bulk layered structure. Figure 3 The scanned electron microscope (SEM) images of the waste NCM811 ternary cathode material, the oxide precursor, and the regenerated NCM811 ternary cathode material in Example 5 are shown. By comparison, it can be seen that the waste material exhibits a mixed morphology of single-crystal and polycrystalline secondary particles. After oxidation, the particles break into primary particles with a particle size of 0.5~1.0 μm, while the regenerated material forms structurally stable single-crystal particles, highlighting the optimization of morphology by the regeneration process.

[0061] Example 6 S1. Selected retired NCM622 (LiNi) 0.6 Co 0.2 Mn 0.2 O2) ternary cathode material, sodium persulfate (Na2S2O8) was added to NaOH solution with pH=13 as oxidant, solid-liquid ratio 1:10, temperature 25℃, reaction for 12h, to obtain oxide precursor with NiOOH layered structure on the surface, the precursor morphology is single crystal particles. S2. Lithium hydroxide (LiOH) and Al and Mg doped salts (aluminum nitrate and magnesium nitrate) were added to the same system, with the molar ratio of lithium source to total metal being 3:1, the molar ratio of Al doping being 0.003:1, and the molar ratio of Mg doping being 0.003:1. The reaction conditions were: temperature 120℃, pressure 0.5 MPa, and time 12h. After washing and drying, the lithium intercalation doped precursor was obtained. S3. The precursor was annealed at 800℃ in a pure oxygen atmosphere for 12 hours to obtain Al / Mg-doped regenerated single-crystal NCM622 material.

[0062] Figure 4 The cycling performance curves of the waste NCM622 ternary cathode material and the recycled NCM622 ternary cathode material in Example 6 are shown. The capacity retention rate of the waste material decays rapidly during cycling, while the capacity retention rate of the recycled material is significantly improved after 100 and 200 cycles, reaching about 98% after 200 cycles. This demonstrates the effectiveness of the regeneration method in improving structural stability and electrochemical performance. Figure 5The scanning electron microscope (SEM) images of the waste NCM622 ternary cathode material, the oxide precursor, and the regenerated NCM622 ternary cathode material in Example 6 are shown. The comparison shows that the waste material has large secondary particle clusters, and the oxidation process causes it to break into dispersed primary particles. In contrast, the regenerated particles have a more uniform and stable morphology, and the particle size is controlled to be below the micrometer level. Figure 6 The cycling performance curves of the waste NCM622 ternary cathode material and the recycled NCM622 ternary cathode material in Example 6 are shown. The discharge capacity of the waste material decreases significantly during cycling, while the capacity retention rate of the recycled material is still as high as about 98% after 200 cycles.

[0063] Example 7 S1. Selected retired NCM523 (LiNi) 0.5 Co 0.2 Mn 0.3 O2) ternary cathode material, sodium persulfate (Na2S2O8) was added to NaOH solution with pH=13 as oxidant, solid-liquid ratio 1:10, temperature 25℃, reaction for 12h, to obtain oxide precursor with NiOOH layered structure on the surface, the precursor morphology is single crystal particles. S2. Lithium hydroxide (LiOH) and Al and Mg doped salts were added to the same system, with the molar ratio of lithium source to total metal being 3:1, the molar ratio of Al doping being 0.003:1, and the molar ratio of Mg doping being 0.003:1. The reaction conditions were: temperature 120℃, pressure 0.5MPa, and time 12h. After washing and drying, the lithium intercalation doped precursor was obtained. S3. The precursor was annealed at 850℃ in a pure oxygen atmosphere for 12 hours to obtain Al / Mg-doped regenerated single-crystal NCM523 material.

[0064] Figure 7 The scanned electron microscope (SEM) images of the waste NCM523 ternary cathode material, the oxide precursor, and the regenerated NCM523 ternary cathode material in Example 6 are shown. It can be observed that the waste material is in a mixed state of particles, and after oxidation, it is transformed into an intermediate composed of primary particles, while the regenerated material exhibits a single crystal morphology, which demonstrates the universal applicability of the process to different NCM composition materials. Figure 8 The cycling performance curves of the waste NCM523 ternary cathode material and the recycled NCM523 ternary cathode material in Example 6 are shown. The capacity decay curve of the waste material is steeper, while the capacity retention rate of the recycled material is about 99% after 200 cycles. This further verifies the advantages of the method of the present invention in restoring electrochemical performance, making the performance of the recycled material close to or better than that of the original commercial material.

[0065] Comparative Example 1 The difference between this comparative example and Example 1 is that step S1 is carried out under the condition of pH=10; The results are as follows Figure 9 As shown, under these conditions, the internal stress does not exceed the grain boundary bonding strength. In Comparative Example 1, the secondary particles still maintain their original dense structure and cannot achieve deagglomeration from secondary particles to primary particles.

[0066] Comparative Example 2 The difference between this comparative example and Example 1 is that step S1 is carried out at a temperature of 80°C. The results are as follows Figure 10 As shown, under these conditions, only surface damage or irregular breakage occurs, without controlled deagglomeration along the grain boundaries, making it impossible to obtain primary particles with uniform particle size and good dispersion.

[0067] Comparative Example 3 This comparative example provides a waste NCM622 (LiNi) 0.6 Co 0.2 Mn 0.2 The pre-oxidation regeneration method for ternary cathode materials (O2) includes the following steps: Pretreatment of waste cathode materials: Waste lithium-ion battery NCM622 (LiNi) materials are pretreated. 0.6 Co 0.2 Mn 0.2 The ternary cathode material (O2) was immersed in a 2 mol / L sodium chloride solution and discharged for 24 h. The battery was then manually disassembled, separating components such as aluminum foil, copper foil, casing, and separator. The stripped cathode sheet was cleaned with dimethyl carbonate (DMC) and then ultrasonically treated in N-methylpyrrolidone (NMP) at a solid-liquid ratio of 100 g / L for 30 min to obtain a suspension containing waste cathode powder. The suspension was placed in a centrifuge tube and centrifuged at 500 rpm for 30 min. The supernatant was discarded, and this process was repeated twice to obtain a precipitated residue (denoted as Be-S-NCM622). Be-S-NCM622 was then calcined at 600℃ for 5 h and ground to obtain waste cathode material powder (denoted as S-NCM622).

[0068] Pre-oxidation regeneration process: Take 5 g of waste cathode material powder (S-NCM622) and place it in 100 mL of deionized water. Add a certain amount of Na2S3O8 and NaOH to ensure that the pH of the reaction system is 10. Stir at 100 rpm for 30 min at room temperature, then filter to obtain filter residue. Wash twice with deionized water and dry the washed filter residue in a vacuum drying oven to obtain the oxidation intermediate.

[0069] Lithium replenishment and calcination: The oxide intermediate was mixed with LiOH·H2O at a ratio of (Ni+Co+Mn) / Li = 1:1.03, ground uniformly, and then calcined at 850℃ for 5 hours in a muffle furnace under an oxygen-enriched atmosphere to obtain the regenerated cathode material (denoted as OR-NCM622). Figure 9 As shown, the recycled NCM622 material exhibits a complete micron-sized secondary spherical particle morphology, which is composed of a large number of densely packed nano-sized primary grains, unlike the primary particles obtained in Example 6.

[0070] The results are as follows Figure 11 As shown, under these conditions, the changes in the internal lattice parameters of the material are limited, and significant elongation in the c-axis direction is not induced. As a result, it is difficult to accumulate sufficient internal stress within the secondary particles to destroy the grain boundaries and maintain the original dense sintered structure. No deagglomeration behavior along the grain boundaries occurs.

[0071] Test case This test case compares the electrochemical cycling performance of the recycled NCM811, NCM622, and NCM523 ternary cathode materials prepared in the examples with that of the original waste NCM811, NCM622, and NCM523 materials.

[0072] The testing method is as follows: Battery assembly: The positive electrode material to be tested is mixed with conductive carbon black and PVDF binder at a mass ratio of 8:1:1 and coated onto aluminum foil. A lithium metal sheet is used as the counter electrode. The CR2032 coin cell is assembled in an argon atmosphere glove box. Electrolyte: A commercial carbonate electrolyte with 1 mol / L LiPF6 dissolved in EC:DEC (volume ratio 1:1) was used. Voltage window: The charge / discharge test voltage range is 3.0~4.3 V; Current density: Constant current charge and discharge at 1C rate (where 1C = 170mA / g for NCM523 and 622, and 1C = 200mA / g for NCM811). Test temperature: Conducted at room temperature (25±2℃); Cycle count: 100, 200 cycles, record the discharge specific capacity and capacity retention rate for each cycle.

[0073] 1. Performance Testing The superior electrochemical performance of the embodiments of this invention is primarily due to a synergistic and efficient regeneration strategy: under strongly alkaline (pH=13) and low-temperature (25~40℃) conditions, a highly active layered NiOOH structure is generated in situ through gentle oxidation, effectively repairing surface defects and opening lithium-ion diffusion channels. Simultaneously, polycrystalline secondary particles are deagglomerated along grain boundaries into 0.5–1.0 μm single-crystal primary particles, achieving uniform in-situ lithium replenishment and doping within the same reaction system. Finally, high-temperature annealing yields a highly ordered regenerated single-crystal cathode material. Example 4 demonstrates the best results; under these conditions, the oxidation process is not only gentler and more controllable but also forms a denser, continuous, and thinner NiOOH interface layer, significantly improving the first-cycle discharge specific capacity and cycle stability. In contrast, the comparative examples performed poorly due to deviations from the core process: Comparative Example 1 suffered from insufficient surface oxidation due to excessively low pH (pH=10) and remained polycrystalline; Comparative Example 2's excessively high reaction temperature (80℃) damaged the bulk structure; and Comparative Example 3 ultimately remained polycrystalline, resulting in significantly inferior cycle performance compared to the embodiments of the present invention. While Comparative Examples 1-3 still consisted primarily of micron-sized secondary particles with a D50 maintained in the 5-15 μm range, the embodiments of the present invention, through the synergistic effect of chemically driven lattice reconstruction and stress-induced deagglomeration, significantly refined the particle size to the submicron scale. The regenerated cathode material transformed from its original polycrystalline structure to a single-crystal structure, with its D50 reduced to 2-5 μm, fully demonstrating the significant technical effects of the present invention in terms of morphology control and particle size controllability of the regenerated cathode.

[0074] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for regenerating waste ternary cathode materials, characterized in that, Includes the following steps: S1. Waste ternary cathode material and oxidant are mixed and reacted in an alkaline system with pH 12.5~14 and temperature 25~50℃ to obtain an intermediate composed of primary particles; The surface of the primary particles has a layered NiOOH structure; The D50 of the primary particles is 0.5~1μm; The intermediate has the molecular formula Li 1-a Ni b Co c Mn d O2, where 0 < a < 1, 0.3 ≤ b ≤ 0.9, 0.05 ≤ c ≤ 0.3, 0.05 ≤ d ≤ 0.3, b + c + d = 1; S2. Add a lithium source and a doped metal salt to the alkaline system to react and obtain a doped lithium-intercalated cathode material precursor; S3. The obtained doped lithium-intercalated cathode material precursor is annealed at high temperature to obtain a regenerated single-crystal cathode material with a doped and modified D50 of 2~5μm.

2. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, Step S1 also includes adding Na2CO3, wherein the amount of Na2CO3 added is 0.01~0.1mol / L.

3. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, The waste ternary cathode contains Li 1-a Ni b Co c Mn d The molar ratio of O2 to the oxidant is 1:0.5 to 2.

5.

4. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, In step S1, the mixing reaction time is 1 to 48 hours, and the solid-liquid mass-volume ratio of the waste ternary cathode material to the alkaline aqueous solution is 1 to 10 g / mL.

5. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, In step S2, the reaction time is 1 to 48 hours, the reaction temperature is 80 to 200°C, and the reaction pressure is 0.1 to 2.0 MPa.

6. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, The lithium source includes soluble lithium salts; The soluble lithium salt includes at least one of lithium acetate, lithium sulfate, lithium nitrate, and lithium hydroxide.

7. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, The doped metal salt includes at least one of Na, Mg, K, Al, or Ca.

8. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, The molar ratio of the dopant element in the doped metal salt to the total metal element in the intermediate composed of the primary particles is 0.001 to 0.05:

1.

9. The method for regenerating waste ternary cathode materials according to claim 1, characterized in that, In step S3, the temperature of the high-temperature annealing is 650-900℃; the time of the high-temperature annealing is 8-20h; and the atmosphere of the high-temperature annealing is air or pure oxygen.

10. The application of a regenerated single-crystal ternary cathode material prepared by any one of claims 1 to 9 in a lithium-ion battery.

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