Method for regenerating high-nickel ternary positive electrode material by liquid phase complexation-surface reconstruction and material

Abstract

This invention discloses a method and materials for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction, belonging to the field of lithium-ion battery cathode material recycling technology. First, a mixed solution of ammonia, ammonium salt, and reducing agent is used to selectively leach the failed high-nickel ternary material, utilizing the reaction of NH3 and Ni... 2+ The coordination effect of the catalyst preferentially dissolves the surface rock salt phase and removes impurities, while simultaneously reducing nickel content. Then, a manganese-containing reagent is used to surface-treat the leached material, constructing a manganese-rich protective layer on the material surface through chemical deposition. Finally, the surface-modified material is mixed with lithium sources recovered from the leaching solution and fresh lithium sources, and sintered at high temperature in an oxygen atmosphere to achieve re-lithiation and single-crystallization, ultimately yielding a cathode material with a surface concentration gradient. This invention achieves synergistic repair and upgrading of failed materials from the bulk phase to the interface. The process is simple, environmentally friendly, and easily scalable. The regenerated material exhibits improved capacity, cycle stability, and rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material recycling technology, and in particular to a method and materials for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction. Background Technology

[0002] High-nickel ternary cathode materials, due to their advantages such as high specific capacity and high energy density, have become key materials for next-generation high-energy-density lithium-ion batteries and are widely used in new energy vehicles, energy storage devices, and other fields. However, during long-term charge-discharge cycles, they are prone to problems such as rapid capacity decay and deterioration in cycle stability, leading to battery failure. The main failure mechanisms include: intensified bulk lithium / nickel mixing; irreversible phase transition from layered structure to rock salt phase on the surface under high voltage, accompanied by lattice oxygen precipitation; microcracks generated inside the particles; and continuous interfacial side reactions between the material and the electrolyte. These failure mechanisms lead to loss of active lithium, increased interfacial impedance, and destruction of structural stability, ultimately rendering the battery unable to meet usage requirements.

[0003] With the rapid development of new energy vehicles and energy storage industries, the amount of waste lithium-ion batteries generated has increased dramatically. Efficient recycling of failed high-nickel ternary cathode materials can not only alleviate resource shortage pressures but also reduce environmental pollution risks.

[0004] Currently, the regeneration strategy for failed high-nickel ternary cathode materials is mostly a simple process of lithium replenishment followed by high-temperature sintering. While this method can restore some capacity, it cannot repair inherent surface and interface defects, resulting in poor cycle performance of the regenerated materials. Some studies have attempted to upgrade the regeneration process by introducing bulk doping or surface coating, but these methods suffer from problems such as complex processes, uneven coating layers, or loss of specific capacity. Therefore, developing a simple and efficient regeneration method that can simultaneously repair the bulk structure and surface interfaces and upgrade material performance has become an urgent need in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for regenerating high-nickel ternary cathode materials that can simultaneously achieve surface repair, bulk regeneration, and performance improvement. This method uses a synergistic process of "selective liquid phase complexation - surface manganese reconstruction - closed-loop relithiation" to not only efficiently recover valuable elements, but also regenerate failed materials into high-performance single-crystal materials with a surface concentration gradient structure.

[0006] This material has a unique gradient structure with decreasing nickel content and increasing manganese content from the bulk phase to the surface, as well as a complete single-crystal morphology, thus possessing high capacity, excellent cycle stability and rate performance.

[0007] To achieve the above objectives, the present invention provides a method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction, specifically comprising the following steps:

[0008] S1. Selective liquid-phase complexation: The failed high-nickel ternary cathode material is mixed with the leachate and reacted. After the reaction is completed, the solid and liquid are separated to obtain the first solid and the first filtrate. The leachate contains ammonia, ammonium salt and reducing agent. The purpose of this reaction is to selectively dissolve the rock salt phase impurities on the surface of the material and the cathode electrolyte interface layer to achieve surface nickel reduction and lithium release.

[0009] S2, Surface manganese deposition: The first solid obtained in step S1 is mixed with a solution containing manganese compounds to carry out a surface deposition reaction. After the reaction is completed, the solid and liquid are separated to obtain a second solid with manganese-rich surface. This step constructs a uniform manganese-rich layer on the material surface, laying the foundation for the formation of a concentration gradient structure.

[0010] S3, Re-lithiation Sintering: The second solid obtained in step S2 is mixed with a lithium source and sintered at high temperature in an oxygen-containing atmosphere to obtain a regenerated single-crystal high-nickel ternary cathode material.

[0011] Preferably, in step S1, the ammonium salt in the leachate is at least one of ammonium carbonate, ammonium bicarbonate, and ammonium sulfate;

[0012] The reducing agent is at least one of ascorbic acid, sodium sulfite, and hydrazine hydrate.

[0013] Preferably, in step S1, the concentration of ammonia in the leachate is 0.5-5 mol / L, the concentration of ammonium salt is 0.1-2 mol / L, and the concentration of reducing agent is 0.05-1 mol / L.

[0014] The reaction temperature is 40-90℃, and the reaction time is 0.5-6h.

[0015] Preferably, in step S2, the manganese-containing compound is at least one of potassium permanganate, manganese sulfate, manganese acetate, and manganese nitrate;

[0016] The surface deposition reaction was carried out with the solution pH controlled between 7 and 11.

[0017] Preferably, in step S3, the lithium source is lithium carbonate or lithium hydroxide.

[0018] Preferably, in step S3, the high-temperature sintering temperature is 850-950℃, the sintering time is 15-25h, and the oxygen-containing atmosphere is pure oxygen atmosphere or air atmosphere.

[0019] Preferably, in step S3, the amount of lithium source used satisfies that the molar ratio of total lithium to transition metal Li / TM after mixing is 1.20-1.40.

[0020] Preferably, before step S3, the method further includes a step of recovering lithium salt from the first filtrate obtained in step S1. Specifically, the first filtrate is heated to 60-90°C to evaporate and concentrate, ammonia is removed and lithium carbonate is crystallized and precipitated, and recovered lithium carbonate is obtained by solid-liquid separation. The recovered lithium carbonate can be used as the lithium source in step S3.

[0021] Preferably, before step S1, a pretreatment step for the failed high-nickel ternary cathode material is included. Specifically, the waste lithium-ion battery is discharged, disassembled and the cathode sheet is separated, the cathode material powder is obtained by peeling with an organic solvent, and then heat-treated at 400-500°C for 4-6 hours to remove residual organic matter.

[0022] The present invention also provides a high-nickel ternary cathode material obtained by the above method, wherein the high-nickel ternary cathode material has a concentration gradient structure in which the Ni content decreases and the Mn content increases from the bulk phase to the surface, and has a single crystal morphology.

[0023] Therefore, the method and materials for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction provided by this invention have the following beneficial effects:

[0024] This invention provides a method for the synergistic regeneration of waste nickel-rich cathodes into high-value single-crystal materials through surface chemical repair and bulk stabilization. In a liquid phase environment of ammonia complexation and surface deposition, unstable surface nickel is precisely removed and an epitaxial protective layer is constructed, simultaneously achieving bulk structure stabilization and efficient recovery of lithium resources.

[0025] First, ammonia is used as a complexing agent. Its selective complexing action can precisely strip away highly active nickel that is unstable on the surface, thereby inhibiting harmful phase transitions and side reactions during the charging and discharging process at the source and achieving surface repair.

[0026] Secondly, a manganese source was introduced into the liquid environment, and a manganese-rich, stable protective layer with epitaxial matching to the bulk structure was constructed in situ through surface deposition. This protective layer not only physically isolates the electrode material from direct contact with the electrolyte, effectively suppressing electrolyte decomposition and the resulting interfacial side reactions, but also significantly inhibits the high-activity Ni during cycling by enhancing surface structural stability and chemical anchoring. 4+ The harmful effects of oxygen release are reduced.

[0027] Furthermore, this invention ingeniously designs a closed-loop resource recycling system. By efficiently recovering and reusing lithium resources in the leachate, it not only reduces raw material costs and the environmental impact of the process, but also achieves resource recycling, which aligns with the concept of a green circular economy.

[0028] Furthermore, this invention organically integrates the three key steps of "surface repair," "bulk phase regeneration," and "resource recycling" into a single, efficient, and synergistic process. The process steps are clear, the conditions are mild, it is easily scaled up, and it possesses significant industrialization potential. Through the synergistic effect of the surface stabilizing protective layer, the bulk phase repair structure, and the resource recycling system, this invention fundamentally solves the problems of interface instability, rapid capacity decay, and low resource utilization during the regeneration of waste nickel-rich materials.

[0029] The monocrystalline cathode material obtained in this invention was assembled into a button cell for testing, and it exhibited excellent electrochemical performance: the first discharge specific capacity at 0.1C rate was as high as 203.08 mAh / g, and it could still maintain a discharge capacity of 137.05 mAh / g at a high rate of 5C. Moreover, after 250 cycles at 1C rate and a voltage range of 2.8-4.5V, the capacity retention rate was as high as 89.75%. Its comprehensive performance is significantly better than that of materials obtained by traditional regeneration methods.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 These are SEM cross-sectional characterization images and EDS linear scan energy dispersive spectra of the gradient single-crystal material in Embodiment 1 of the present invention. The surrounding small particles are C materials that need to be modulated into electrode form for testing purposes. Among them, a is the SEM cross-sectional characterization image and b is the EDS linear scan energy dispersive spectra.

[0032] Figure 2 These are SEM characterization images of Comparative Examples 1-2 and Example 1 of the present invention;

[0033] Figure 3 These are XRD characterization images of the failed high-nickel ternary cathode material obtained after pretreatment in the embodiments of the present invention, as well as the final products obtained in Example 1 and Comparative Examples 1-2;

[0034] Figure 4 This is a comparison of the first charge-discharge curves of the batteries corresponding to the gradient single-crystal materials in Examples 1-4 of this invention at 0.1C.

[0035] Figure 5 These are comparison graphs of the cycle curves of the batteries corresponding to the high-value single-crystal materials in Examples 1-4 of this invention;

[0036] Figure 6 This is a comparison chart of the rate performance of the batteries corresponding to the high-value monocrystalline materials in Examples 1-4 of this invention;

[0037] Figure 7 These are EIS test images of the failed high-nickel ternary cathode material obtained after pretreatment in the embodiments of the present invention, the gradient single crystal material obtained in Comparative Example D1 and Example 1;

[0038] Figure 8 These are GITT test images of the failed high-nickel ternary cathode material obtained after pretreatment in the embodiments of the present invention, the gradient single crystal material obtained in Comparative Example D1 and Example 1. Detailed Implementation

[0039] This invention provides a method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction, comprising the following steps:

[0040] S1. Selective liquid-phase complexation: The failed high-nickel ternary cathode material is mixed with the leachate and reacted at 40-90℃ for 0.5-6h. After solid-liquid separation, the first solid and the first filtrate are obtained. The leachate contains ammonia water with a concentration of 0.5-5mol / L, ammonium salt with a concentration of 0.1-2mol / L, and reducing agent with a concentration of 0.05-1mol / L.

[0041] S2. Surface manganese deposition: The first solid is mixed with a solution containing manganese compounds, and the pH is controlled between 7 and 11 to carry out the surface deposition reaction. After the reaction is completed, the solid and liquid are separated, washed and dried to obtain a second solid with manganese-rich surface.

[0042] S2, Re-lithiation Sintering: The second solid with manganese-rich surface is mixed with lithium source and flux, and sintered at 880-950℃ for 15-20h in an oxygen-containing atmosphere to obtain regenerated high-value single-crystal nickel-rich cathode material.

[0043] In this invention, before step S1, a pretreatment step for the failed high-nickel ternary cathode material is included, specifically including:

[0044] (1) Discharge the waste lithium-ion battery in a 0.5-1.5 mol / L sodium chloride solution until the voltage is below 1.5 V, disassemble and separate to obtain the positive electrode sheet.

[0045] (2) The positive electrode sheet is peeled off in N-methylpyrrolidone solvent at 60-80℃ for 4-6h, and the positive electrode active material powder is obtained after solid-liquid separation.

[0046] The stripping process was performed with ultrasonic assistance at a frequency of 20-90 kHz; the solid obtained after solid-liquid separation was dried under vacuum at 65-75℃ for 8-12 hours.

[0047] (3) Heat-treat the positive electrode active material powder at 400-500℃ for 4-6h to remove organic residues and obtain the pretreated high-nickel ternary positive electrode material.

[0048] The heat treatment process includes ball milling and sieving of the material; the ball milling speed is 400-600 r / min, the ball milling time is 2.5-3.5 h, and the sieve mesh size is 500-800 mesh.

[0049] In this invention, prior to step S3, a step of recovering lithium salt from the first filtrate obtained in step S1 is included. Specifically, the first filtrate is heated to 60-90°C for evaporation and concentration to remove ammonia and promote the crystallization of lithium carbonate. The recovered lithium carbonate is then obtained through solid-liquid separation. The recovered lithium carbonate can be used as the lithium source in step S3. The lithium source also includes additional fresh lithium carbonate or lithium hydroxide to ensure that the molar ratio of the total lithium content to the transition metal content meets the stoichiometric requirements (Li / TM = 1.2-1.4).

[0050] In this invention, the ammonium salt is at least one of ammonium carbonate, ammonium bicarbonate, or ammonium sulfate; the reducing agent is at least one of ascorbic acid, sodium sulfite, or hydrazine hydrate.

[0051] In this invention, the manganese-containing compound is at least one of manganese sulfate, manganese acetate, manganese nitrate, or potassium permanganate.

[0052] In this invention, the relithiation sintering is carried out in an oxygen or air atmosphere, preferably a pure oxygen atmosphere; the sintering temperature is 880-950℃, and the holding time is 15-20h.

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0054] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0055] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0056] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art, and the testing standards all use national or international standards commonly used in the field, without further explanation.

[0057] In the following embodiments and comparative examples of the present invention, waste lithium-ion batteries LiNi 0.8 Co 0.1 Mn 0.1 O2 is obtained from discarded 10Ah pouch cells through a pretreatment method using failed high-nickel ternary cathode materials (the discarded 10Ah pouch cells were provided by Shaanxi Ruizhi New Energy Technology Co., Ltd.).

[0058] Example 1

[0059] This embodiment provides a method for regenerating high-nickel ternary cathode materials through liquid-phase complexation and surface reconstruction. The specific steps are as follows:

[0060] S1. Preprocessing:

[0061] (1) Dispose of used 10Ah soft-pack lithium-ion batteries (LiNi) 0.8 Co 0.1 Mn 0.1 The O2 positive electrode was placed in a 1.0 mol / L sodium chloride solution and discharged to a voltage of 1.2 V. After disassembly, the positive electrode sheet was obtained.

[0062] (2) The positive electrode sheet was placed in N-methylpyrrolidone solvent and peeled for 5 hours under ultrasonic assistance at 70℃ and 50kHz. After solid-liquid separation, the solid was dried under vacuum at 70℃ for 10 hours to obtain positive electrode active material powder.

[0063] (3) The positive electrode active material powder was heat-treated at 450°C for 5 hours, then ball-milled at 500 r / min for 3 hours, and passed through a 600 mesh sieve to obtain the pretreated high-nickel ternary positive electrode material.

[0064] S2. Selective liquid-phase complexation: Take 10g of pretreated failed high-nickel ternary cathode material and react it with 200mL of leachate (containing 2mol / L ammonia, 1mol / L ammonium carbonate, and 0.2mol / L ascorbic acid) at 60℃ under N2 atmosphere for 2 hours. After the reaction, centrifuge and wash the solid three times with deionized water. Dry it at 80℃ to obtain the first solid. Heat the first filtrate to 85℃ to evaporate and concentrate it until a large amount of white precipitate is precipitated. Filter and dry to obtain recovered lithium carbonate.

[0065] S3. Surface manganese deposition: The first solid was dispersed in 200 mL of deionized water, 0.05 mol of manganese sulfate was added, and 1 mol / L NaOH solution was added dropwise while stirring. The pH was controlled to 9.0 and the reaction was carried out for 1 hour. After centrifugation, washing and drying, a second solid with manganese enrichment on the surface was obtained.

[0066] S4. Lithium source recovery: The first filtrate is heated and evaporated at 80°C to remove ammonia and promote the crystallization of lithium carbonate to recover lithium carbonate.

[0067] S5. Re-lithiation sintering: The content of Li and transition metals (TM = Ni + Co + Mn) in the second solid is determined by ICP, and its Li / TM molar ratio is calculated; based on the target product LiNi 0.8 Co 0.1 Mn 0.1 The required amount of lithium to be added was calculated based on the stoichiometric ratio of O2 (Li / TM=1.3). The second solid, the recovered lithium carbonate, and the fresh lithium carbonate were precisely mixed. The mixture was placed in an alumina crucible and heated to 850°C at 3°C / min in an oxygen atmosphere, held at that temperature for 10 hours, and then cooled in the furnace. The mixture was then ground and sieved to obtain the regenerated high-value single-crystal NCM811 material, denoted as sample S1.

[0068] Example 2 (Optimized Leaching Temperature)

[0069] The only difference between this embodiment and Example 1 is that the reaction temperature in the selective liquid phase complexation step S2 is increased to 80°C and the reaction time is shortened to 1 hour. All other aspects are the same as in Example 1 and will not be repeated here. The resulting recycled material is referred to as sample S2.

[0070] Example 3 (Adjusting the amount of manganese deposited)

[0071] The only difference between this embodiment and Embodiment 1 is that the amount of manganese sulfate added is changed in step S3, which involves surface manganese deposition. Two groups were set up: a low-manganese group with 0.02 mol of manganese sulfate added, and a high-manganese group with 0.08 mol of manganese sulfate added. All other aspects were the same as in Embodiment 1 and will not be repeated here. The recycled materials obtained from the low-manganese group and the high-manganese group were designated as samples S3-L and S3-H, respectively.

[0072] Example 4 (Treatment of raw materials with different degrees of failure)

[0073] This embodiment uses two NCM811 raw materials with different failure levels: raw material A (electrode recovery powder with a capacity retention of ~70% after 1000 cycles) and raw material B (recovery powder from pouch cells damaged by over-discharge). Both raw materials underwent the same pretreatment and were regenerated using the exact same steps as in Example 1. The regenerated materials obtained from raw material A and raw material B are designated as samples S4-A and S4-B, respectively.

[0074] Comparative Example 1 (Direct Regeneration Method)

[0075] This comparative example provides a method for direct high-temperature solid-phase regeneration of high-nickel ternary cathode materials, including the following steps:

[0076] S1. Take 10g of expired NCM811 powder from the same source as in Example 1 (treated by the S1 pretreatment step in Example 1), without selective liquid-phase complexation and surface manganese deposition, and use it directly as a regeneration precursor.

[0077] S2, Re-lithiation Sintering: ICP testing of the elemental content of the failed NCM811 powder revealed that its Li / TM ratio had significantly deviated from the original stoichiometric ratio (measured Li / TM≈0.74); based on the target product LiNi 0.8 Co 0.1 Mn 0.1 Calculate the stoichiometric ratio of O2 (Li / TM=1.3) and add sufficient fresh lithium carbonate; place the mixture in a corundum crucible, heat it to 850°C at a rate of 3°C / min under a pure oxygen atmosphere, hold it at that temperature for 15 hours, and then cool it to room temperature with the furnace.

[0078] S3. Post-processing: Grind the sintered bulk material and pass it through a 600-mesh sieve to obtain regenerated cathode material powder, denoted as sample D1.

[0079] Comparative Example 2 (Leaching Method Only)

[0080] This comparative example provides a method for regenerating high-nickel ternary cathode materials using only selective leaching. The steps S1, S2, S4, and S5 are identical to those in Example 1, except for the absence of the surface manganese deposition process in step S3. The obtained first solid is used directly as a regeneration precursor, and its elemental content is determined by ICP testing to calculate its Li / TM ratio. Based on the target product stoichiometry (Li / TM = 1.3), the first solid is precisely mixed with recovered lithium carbonate and a necessary amount of fresh lithium carbonate. Subsequent sintering and post-treatment yield the regenerated cathode material, denoted as sample D2.

[0081] Performance Testing and Results Analysis

[0082] 1. Testing and characterization methods:

[0083] Phase analysis was performed on the materials obtained in the above examples and comparative examples using a STOE X-ray diffractometer (scanning range 5°-30°). The surface morphology of the materials was characterized using a Helios G4CX scanning electron microscope (SEM). The atomic distribution characteristics of key elements (Ni, Co, Mn) along the Fib section of the samples were analyzed using the line scan mode of its matching energy dispersive X-ray spectrometer (EDS).

[0084] The recycled materials obtained in the above examples and comparative examples were assembled into CR2016 button batteries. Recycled materials, polyvinylidene fluoride binder, and SuperP conductive agent were added sequentially to N-methyl-2-pyrrolidone at a mass ratio of 8:1:1 and mixed to obtain a black slurry with a solid content of 40%. The black slurry was coated onto aluminum foil and vacuum dried at 60°C for 12 hours. After drying, the solid content on the aluminum foil (the solid content of the dried black slurry) was approximately 4.5 mg / cm³. 2 The lithium sheet is stamped into a 12mm diameter disc as the positive electrode, a lithium sheet is used as the negative electrode, Celgard 2500 is used as the separator between the positive and negative electrodes, and LB-037 is used as the electrolyte to assemble a CR2016 button battery.

[0085] Charge and discharge tests (voltage 2.8~4.5V) were conducted using the Xinwei Battery Testing System to test the initial capacity at 0.1C, performance at different rates (0.1, 0.5, 1, 2, 5C), and capacity retention rate after 200 cycles at 1C.

[0086] 2. Test Result Analysis:

[0087] (1) Morphological and structural characterization

[0088] Figure 1 Figure 'a' shows the SEM cross-sectional morphology of Example 1 on the electrode, with the particles appearing as individual particles of about 2 μm.

[0089] The accompanying energy-dispersive X-ray spectroscopy (EDS) line scan mode was used to analyze the atomic distribution characteristics along the path of key elements (Ni, Co, Mn) in the Fib section of the sample. The results are as follows: Figure 1 As shown in b, Mn elements are found to be enriched on the surface and gradually decrease in the interior, while Co and Ni atoms decrease on the surface and increase in the interior of the particles.

[0090] Figure 2SEM images of the samples obtained in Example 1 and Comparative Examples 1-2 are shown. Comparative Example 1 omitted the core "selective leaching-manganese reconstruction" step, and the residual lithium compounds (Li2CO3, LiOH), irreversible phase (rock salt phase), and lithium depletion in the bulk phase on the surface of the failed material were not effectively repaired or compensated. Although direct high-temperature sintering can partially recrystallize the crystal structure, it cannot eliminate the original grain boundary defects and microcracks, and excessive lithium salt may react with surface impurities to form an inert layer. The final product D1 is a polycrystalline agglomerate with fine grains, poor fusion, and many surface residues. Comparative Example 2 selectively leached away some surface impurities and recovered lithium, but the repaired material D2 lacked the "manganese source" and "structure guide" introduced by manganese deposition in Example 1. In the subsequent sintering process, the particles lacking heterogeneous nucleation points could not undergo sufficient grain boundary migration and fusion, and could not effectively grow into large single crystals with uniform size. The product morphology was polycrystalline or quasi-single crystal particles with rough surfaces, partial fusion, but clear grain boundaries. Example 1 (S1) shows distinct and dispersed single-crystal particles.

[0091] Figure 3 The XRD patterns of the failed high-nickel ternary cathode material obtained in step S1 of Example 1, as well as the samples obtained in Example 1 and Comparative Examples 1-2, are shown. As shown in the figure, all samples exhibit a typical layered α-NaFeO2 structure. However, the intensity ratio of the (003) to (104) diffraction peaks (I003 / I104) of the sample in Example 1 is significantly higher than that of the comparative examples, indicating that it has the lowest cation mixing degree.

[0092] (2) Electrochemical performance test results

[0093] Figure 4-6 The electrochemical performance data of the batteries corresponding to the gradient single crystal materials in Examples 1-4 of the present invention are shown in Table 1. The performance comparison data is shown in Table 1.

[0094] In Experiment 2, while ensuring selective leaching, increasing the temperature could potentially shorten the reaction time or improve impurity removal efficiency, thereby further optimizing the performance of the recycled material. In Experiment 3, different amounts of Mn modification directly affect the induction of single-crystal growth and the chemical state of the material surface during subsequent sintering. By setting different gradients, the range of manganese modification required to obtain optimal electrochemical performance can be explored, providing a basis for process control. Experiment 4 demonstrates that the recycling process of this invention is not only applicable to materials with specific failure modes, but also has good repair and upgrading capabilities for waste nickel-rich materials with different microstructural damage and compositional deviations caused by cyclic decay or abuse, reflecting the robustness and industrial application potential of this method.

[0095] Table 1: Performance Comparison Data of Various Embodiments and Comparative Examples

[0096]

[0097] Depend on Figure 4-6 As can be seen from the data in Table 1, the batteries corresponding to the high-value single-crystal materials obtained in Examples 1-4 of this invention are significantly better than the comparative materials in terms of initial efficiency capacity, high rate performance and long cycle stability, especially the materials in the examples that simultaneously use ammonia leaching and Mn deposition. Table 2 summarizes the differences between the examples and the comparative examples, proving the excellent effect of liquid phase complexation and surface reconstruction regeneration.

[0098] Table 2: Differences between various embodiments and comparative examples

[0099]

[0100] The failed high-nickel ternary cathode material (Spent) obtained after pretreatment in the examples, the single-crystal material obtained in Comparative Example 1 and Example 1 were subjected to electrochemical impedance spectroscopy (EIS Gamry, frequency 0.01~100kHz, amplitude 5mV) to obtain the EIS test patterns of the failed high-nickel ternary cathode material obtained after pretreatment in the examples, and the single-crystal material in Comparative Example 1 and Example 1, as shown below. Figure 7 As shown. From Figure 7 As can be seen, constructing Mn-rich conductive networks can be achieved in LiNi 0.8 Co 0.1 Mn 0.1 The surface of O2 particles provides a rapid ion diffusion pathway and reduces the degradation of single-crystal LiNi due to its large particle size. 0.8 Co 0.1 Mn 0.1 The charge transfer impedance of S1 is significantly lower than that of waste NCM material and comparative example D1.

[0101] The failed high-nickel ternary cathode material obtained after pretreatment in the examples, and the single-crystal materials obtained in Comparative Example 1 and Example 1 were subjected to constant current intermittent titration tests (GITT, Xinwei Battery Testing System, rate 0.1C, voltage 2.8~4.5V) to obtain the GITT test charts of the failed high-nickel ternary cathode material obtained after pretreatment in the examples, and the gradient single-crystal materials of Comparative Example 1 and Example 1, as shown below. Figure 8 As shown. From Figure 8 As can be seen from the data, the lithium-ion diffusion rate (D) of the high-value single-crystal material in Example 1 is [data missing]. Li + The lithium ion diffusion kinetics of the gradient single-crystal material are higher than those of the single-crystal material in Comparative Example 1 and the failed high-nickel ternary cathode material in Example 1, indicating that the gradient single-crystal material has faster lithium ion diffusion kinetics.

[0102] Therefore, this invention provides a method for regenerating waste nickel-rich cathodes into single-crystal materials through selective leaching with ammonia complexes and gradient manganese reconstruction. The core of this method lies in a three-step synergistic process of "selective repair-gradient reconstruction-directional growth": First, ammonia complexes are used to selectively leach residual lithium and impurities from the surface, achieving preliminary purification and simultaneous recovery of lithium resources; second, controlled surface manganese deposition constructs a manganese-rich gradient layer on the surface of the repaired particles, which serves as both a "seed" for subsequent single-crystal growth and a "buffer layer" for stabilizing the interface; finally, in an oxygen-rich atmosphere, this gradient layer guides the particles to undergo directional grain boundary fusion and recrystallization at high temperatures, thereby directly regenerating them into high-performance single-crystal materials with complete structure and uniform composition. This process perfectly combines the selectivity of "hydrometallurgy" with the reconstruction capability of "high-temperature solid-state," achieving the upgrading and regeneration of waste polycrystalline materials into high-value single-crystal products with a simplified process.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction, characterized in that, Specifically, the following steps are included: S1. Selective liquid phase complexation: The failed high-nickel ternary cathode material is mixed with the leachate and reacted. After the reaction is completed, the solid and liquid are separated to obtain the first solid and the first filtrate. The leachate contains ammonia, ammonium salt and reducing agent. Ammonia acts as a complexing agent. Its selective complexing effect can accurately strip the surface-unstable high-activity nickel, thereby inhibiting harmful phase transitions and side reactions during the charging and discharging process at the source and achieving surface repair. S2, Surface manganese deposition: The first solid obtained in step S1 is mixed with a solution containing manganese compound to carry out a surface deposition reaction. After the reaction is completed, the solid and liquid are separated to obtain a second solid with a surface rich in manganese. S3, Re-lithiation Sintering: The second solid obtained in step S2 is mixed with a lithium source and sintered at high temperature in an oxygen-containing atmosphere to obtain a regenerated single-crystal high-nickel ternary cathode material. In step S1, the ammonium salt in the leachate is at least one of ammonium carbonate, ammonium bicarbonate, and ammonium sulfate; the reducing agent is at least one of ascorbic acid, sodium sulfite, and hydrazine hydrate; the reaction temperature is 40-90℃, and the reaction time is 0.5-6h. The concentration of ammonia in the leachate is 0.5-5 mol / L, the concentration of ammonium salt is 0.1-2 mol / L, and the concentration of reducing agent is 0.05-1 mol / L.

2. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: In step S2, the manganese-containing compound is at least one of potassium permanganate, manganese sulfate, manganese acetate, and manganese nitrate. The surface deposition reaction was carried out with the solution pH controlled between 7 and 11.

3. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: In step S3, the lithium source is lithium carbonate or lithium hydroxide.

4. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: In step S3, the high-temperature sintering temperature is 850-950℃, and the sintering time is 15-25h; the oxygen-containing atmosphere is pure oxygen atmosphere or air atmosphere.

5. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: In step S3, the amount of lithium source used satisfies the requirement that the molar ratio of total lithium to transition metal, Li / TM, after mixing is 1.20-1.

40.

6. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: Before step S3, there is also a step of recovering lithium salt from the first filtrate obtained in step S1. Specifically, the first filtrate is heated to 60-90°C to evaporate and concentrate, ammonia is removed and lithium carbonate is crystallized and precipitated. The recovered lithium carbonate is obtained by solid-liquid separation and can be used as the lithium source in step S3.

7. The method for regenerating high-nickel ternary cathode materials through liquid-phase complexation-surface reconstruction according to claim 1, characterized in that: Before step S1, there is also a step of pre-treating the failed high-nickel ternary cathode material. Specifically, the waste lithium-ion battery is discharged, disassembled and the cathode sheet is separated. The cathode material powder is obtained by peeling with an organic solvent and then heat-treated at 400-500℃ for 4-6 hours to remove residual organic matter.

8. A high-nickel ternary cathode material, characterized in that: The high-nickel ternary cathode material is obtained by regeneration using the method described in any one of claims 1-7, and the high-nickel ternary cathode material has Ni content from the bulk phase to the surface. 2+ Decreasing content, Mn 4+ It exhibits a concentration gradient structure with increasing content and a single-crystal morphology.

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