Hydrothermal reconstruction-precise lithium supplement process

Abstract

The invention discloses a hydrothermal reconstruction-precise lithium supplement process, and belongs to the technical field of waste battery recycling. The invention relates to a hydrothermal reconstruction-precise lithium supplement process, which comprises the following steps: (1) sintering and sieving a positive plate in a waste lithium ion battery to obtain D-NCM111; (2) adding water into the D-NCM111 for hydrothermal reaction, and then sequentially washing and drying to obtain a hydrothermal product (H-NCM111); (3) adding the hydrothermal product (H-NCM111) and a lithium source into a solvent, and grinding to obtain a lithium-supplemented product (H-NCM111-Li); and (4) annealing the lithium-supplemented product (H-NCM111-Li) to obtain a regenerated material (R-NCM111). The layered structure of the material is repaired by a hydrothermal method, the consumption of a lithium source is reduced, the crystal structure and electrochemical performance of the NCM111 material are recovered, the first-circle discharge specific capacity at 1C multiplying power reaches about 138mAh g <-1 >, the 100-time 1C multiplying power charge-discharge cycle stability is basically equivalent to that of a commercial C-NCM111 material, and the cycle stability is good. The process is simple, energy consumption and pollution emission are reduced, and the industrial application potential is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste battery recycling and reuse, and particularly relates to a hydrothermal reconstruction-precise lithium supplement process. BACKGROUND

[0002] Battery recycling technologies mainly include pyrometallurgy, hydrometallurgy, bio-metallurgy and direct regeneration technology, each of which has its own characteristics in resource reuse and environmental protection.

[0003] Pyrometallurgy is a traditional recycling process, which has the advantages of large processing capacity, strong adaptability to raw materials and high recovery rate of valuable metals. At the same time, this method can realize the reuse of part of the materials. However, pyrometallurgy also has obvious disadvantages, such as high energy consumption, generation of pollutants such as waste gas and waste residue in the process, large equipment investment, and inability to achieve selective recovery, which may lead to resource waste.

[0004] Hydrometallurgy extracts valuable metal elements through chemical reactions, has the characteristics of high metal recovery rate and high resource reuse degree. In addition, hydrometallurgy has a wide range of applications, and has certain advantages in environmental protection compared with pyrometallurgy. However, this method is relatively complex to operate, has high energy consumption, and needs to consume a large amount of chemical reagents, resulting in rising costs. In addition, the requirements for equipment are also relatively high.

[0005] Bio-metallurgy, as an emerging green recycling technology, uses microorganisms or their metabolites to extract metal elements from waste batteries. It has the advantages of low cost, less pollution and low energy consumption, and microorganisms can be reused. However, the limitations of bio-metallurgy are that it takes a long time to cultivate and use microorganisms, and the reaction time is also relatively long. The cultivation of high-efficiency microbial bacteria is difficult, and the extraction conditions are difficult to accurately control, which limits the possibility of its large-scale application.

[0006] Direct regeneration technology is a new type of battery recycling method that has emerged in recent years, and the core goal is to achieve efficient resource recycling while maximizing the performance of the original material. This technology has the advantages of high resource recovery efficiency, relatively low cost, low energy consumption, and is more environmentally friendly; but at the same time, it also has the disadvantages of high technical requirements, difficulty in removing impurities, limited scope of application, and the structure, electrochemical performance and stability of the regenerated material are difficult to guarantee.

[0007] Therefore, there is an urgent need to provide a new hydrothermal reconstruction-precise lithium supplement process to solve the core problems of lithium source waste, structural damage, unstable electrochemical performance and complex process in existing positive electrode material regeneration technology. SUMMARY

[0008] In view of the above technical problems, the present application provides a hydrothermal reconstruction-precise lithium supplementing process.

[0009] To achieve the above object, the present application provides the following technical solutions.

[0010] One of the technical solutions of the present application is:

[0011] A hydrothermal reconstruction-precise lithium supplementing process, comprising the following steps:

[0012] (1) sintering the positive electrode sheet in the waste lithium ion battery, sieving, to obtain D-NCM111;

[0013] (2) adding water to the D-NCM111 for hydrothermal reaction, and then sequentially performing water washing and drying to obtain a hydrothermal product (H-NCM111);

[0014] (3) adding the hydrothermal product (H-NCM111) and a lithium source into a solvent, grinding, to obtain a lithium supplementing product (H-NCM111-Li);

[0015] (4) annealing the lithium supplementing product (H-NCM111-Li) to obtain a regenerated material (R-NCM111).

[0016] Optionally, the sintering condition in step (1) is sintering at 550 DEG C for 4 hours.

[0017] Beneficial effects: The retired lithium ion battery is disassembled and sintered in the present application, which can remove the organic binder and other impurities in the positive electrode sheet, and prepare for the subsequent hydrothermal reaction.

[0018] Optionally, the dosage ratio of the D-NCM111 to water in step (2) is 1000mg-2000mg: 30ml; preferably 1000mg: 30ml.

[0019] Optionally, the hydrothermal reaction condition in step (2) is 200 DEG C for 3 hours.

[0020] Beneficial effects: Under the hydrothermal reaction condition defined in the present application, without adding a lithium source, the lithium, nickel, cobalt and manganese elements in the D-NCM111 will be redistributed and structurally adjusted under the condition of high temperature and high pressure, and the impurity phase on the surface of the material will be removed, reducing the particle agglomeration, thereby realizing the preliminary recovery of the material structure. This step does not need to add an additional lithium source, avoiding the problems of lithium source waste and the generation of grain boundary impurity phases caused by excessive lithium, and avoiding the waste liquid treatment of a large amount of lithium solution.

[0021] Optionally, the drying condition in step (2) is 80-120 DEG C for 10 hours under vacuum.

[0022] Optionally, the amount of lithium, nickel, cobalt and manganese in the hydrothermal product (H-NCM111) is determined by ICP in step (3), and the amount of the added lithium source needs to meet:

[0023] The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in H-NCM111-Li is 1.00-1.15, preferably 1.00, 1.05, 1.10, 1.15; more preferably 1.10.

[0024] Further, the solvent is anhydrous ethanol.

[0025] Beneficial effects: The purpose of the lithium supplementing step defined in the present application is to accurately adjust the lithium content in the material, thereby changing the original stoichiometric ratio of the waste material. ICP determination can accurately obtain the content of each element in the material, thereby realizing precise lithium supplementing. The addition of anhydrous ethanol helps to improve the uniformity of the material during the grinding process.

[0026] Further, the lithium source is lithium hydroxide monohydrate (LiOH·H2O) or lithium carbonate.

[0027] Optionally, the conditions in the annealing process in step (4) are: heating to 800℃ at a rate of 5℃ / min in air atmosphere, holding for 5h and then cooling to room temperature with the furnace.

[0028] Beneficial effects: The annealing process defined in the present application not only supplements lithium source into the crystal structure, but also further eliminates defects in the material, thereby improving the crystallinity and electrochemical performance of the material.

[0029] Technical solution two of the present application:

[0030] A regenerated material for assembling a button-type half cell, prepared by the above hydrothermal reconstruction-precise lithium supplementing process.

[0031] Technical solution three of the present application:

[0032] A button-type half cell, in which the above regenerated material is used as the active material in the positive electrode.

[0033] Compared with the prior art, the present application has the following advantages and technical effects:

[0034] (1) Reducing lithium source consumption cost

[0035] By repairing the crystal structure of the material through hydrothermal reaction, the defect of adding excessive LiOH or Li2CO3 in the traditional method is avoided, and the cost of lithium source is reduced.

[0036] (2) Restoring the crystal structure and performance of the material

[0037] The NCM111 layered structure was reconstructed under mild hydrothermal conditions (200℃, 3 hours), combined with precise lithium recovery by annealing, so that the specific capacity of the regenerated material recovered to 138mAh g -1 The capacity retention rate is higher after 100 cycles.

[0038] (3) Simplify the process and reduce pollution

[0039] The multi-step precipitation and extraction process of traditional hydrometallurgy is omitted, reducing the discharge of waste acid / alkali solution, while avoiding the high-temperature energy consumption (1200℃→800℃) of pyrometallurgy, reducing CO2 emissions.

[0040] (4) Realize industrialized efficient production

[0041] Determine the lithium content by ICP to accurately supplement lithium, ensure uniformity of lithium distribution, avoid the formation of grain boundary impurity phases caused by excessive lithium, make the regenerated material consistent, and meet the needs of large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and are not intended to limit the present application. In the drawings:

[0043] Figure 1 In (a) and (b) are D-NCM111, (c) and (d) are H-NCM111, (e) and (f) are R-NCM111-1.10, (g) and (h) are SEM images of C-NCM111 samples;

[0044] Figure 2 ICP test column chart of H-NCM111 prepared by adding 3mol / L, 4mol / L, 5mol / L and 0mol / L respectively in the hydrothermal reaction of Comparative Example 1;

[0045] Figure 3 In (a) are XRD patterns of C-NCM111, D-NCM111, R-NCM111-1.10, H-NCM11110-80°, (b) are XRD patterns of 18-20°, (c) are XRD patterns of 64-67°;

[0046] Figure 4 XPS spectra of Ni, Co and Mn elements in C-NCM111, D-NCM111, R-NCM111-1.10, H-NCM111; Wherein (a) is Ni, (b) is Co, (c) is Mn;

[0047] Figure 5The electrochemical cycle performance test chart of the button cell made for C-NCM111, D-NCM111 and NCM111 regenerated in example 1 with different lithium supplementing amounts as variables;

[0048] Figure 6 The first three cyclic voltammetry test charts of D-NCM111;

[0049] Figure 7 The first three cyclic voltammetry test charts of R-NCM111-1.10;

[0050] Figure 8 The electrochemical impedance chart of D-NCM111, R-NCM111-1.10, C-NCM111;

[0051] Figure 9 The discharge specific capacity chart of D-NCM111 and R-NCM111-1.10 at different rates. DETAILED DESCRIPTION

[0052] The existing waste lithium battery regeneration process at present often supplements lithium in a hydrothermal process, but for ternary batteries, supplementing lithium in the hydrothermal process will greatly increase the consumption of lithium on the one hand, and on the other hand, due to the small interlayer spacing of NCM111 layered material, it is difficult for lithium ions to be embedded in the layered structure, and the reaction barrier is large, resulting in poor lithium supplementing effect, and the electrochemical performance of ternary lithium ion batteries cannot be well restored. In view of this, the timing of lithium supplementing is creatively changed, and a hydrothermal reconstruction-precise lithium supplementing process is disclosed, comprising the following steps:

[0053] (1) sintering the positive plate in the waste lithium ion battery, sieving, to obtain D-NCM111;

[0054] (2) adding water to the D-NCM111 to perform a hydrothermal reaction, and then sequentially performing water washing and drying to obtain a hydrothermal product (H-NCM111);

[0055] (3) adding the hydrothermal product (H-NCM111) and a lithium source into a solvent, and performing grinding to obtain a lithium supplementing product (H-NCM111-Li);

[0056] (4) annealing the lithium supplementing product (H-NCM111-Li) to obtain a regenerated material (R-NCM111).

[0057] In an optional embodiment, the sintering condition in step (1) is sintering at 550 DEG C for 4 hours, which can remove the organic binder and other impurities in the positive plate, and prepare for the subsequent hydrothermal reaction.

[0058] In an optional embodiment, the amount ratio of the D-NCM111 and water in step (2) is 1000-2000 mg:30 ml.

[0059] In an optional embodiment, the hydrothermal reaction process in step (2) is carried out at 200°C for 3 hours. Under this hydrothermal reaction condition, the lithium, nickel, cobalt and manganese in the D-NCM111 are redistributed and the structure is adjusted under high temperature and high pressure, and the impurity phase on the surface of the material is removed, the particle agglomeration is reduced, and thus the preliminary recovery of the material structure is achieved. This step does not require additional lithium source, which avoids the waste of lithium source and the problem of impurity phase generated at the grain boundary caused by excessive lithium, and also avoids the waste liquid treatment of a large amount of lithium solution.

[0060] In an optional embodiment, the drying process in step (2) is carried out at 80-120°C for 10 hours under vacuum.

[0061] In an optional embodiment, the amount of lithium, nickel, cobalt and manganese in the hydrothermal product (H-NCM111) is determined by ICP in step (3), and the amount of the lithium source added needs to meet:

[0062] The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in the H-NCM111-Li is 1.00-1.15, preferably 1.00, 1.05, 1.10, 1.15, and more preferably 1.10. The purpose of the limited lithium supplement step is to accurately adjust the lithium content in the material, so as to change the original stoichiometric ratio of the waste material. The content of each element in the material can be accurately obtained by ICP determination (conventional technology), so as to achieve accurate lithium supplement.

[0063] In a preferred embodiment, the solvent is anhydrous ethanol. The addition of anhydrous ethanol helps to improve the uniformity of the material in the grinding process.

[0064] In a preferred embodiment, the lithium source is lithium hydroxide monohydrate (LiOH-H2O) or lithium carbonate.

[0065] In an optional embodiment, the annealing process in step (4) is carried out at a rate of 5°C / min to 800°C in an air atmosphere, and then the furnace is cooled to room temperature after holding for 5h. This annealing process can supplement the lithium source into the crystal structure, further eliminate the defects in the material, and improve the crystallinity and electrochemical performance of the material.

[0066] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0067] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentration, intensity, or molecular weight, an intermediate value of the range can be specifically recited; the inclusion of an intermediate value for a range of values of this type is expressly contemplated even though, for clarity purposes, the intermediate value might not be listed in the range. The upper and lower limits of these smaller ranges can independently be included or excluded in the ranges.

[0068] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, and publications mentioned herein are incorporated by reference for the disclosure and description thereof to the extent that such incorporation does not conflict with the explicit teachings of this specification. Although the foregoing application has been described in some detail by way of illustration and example for purposes of clarity and the certain embodiments of the application have been described above, it is readily apparent to those of ordinary skill in the art in light of the teachings of this application that other embodiments and / or modifications can be made without departing from the scope and spirit of this application.

[0069] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The examples and embodiments described herein are exemplary only and are not intended to be limiting.

[0070] With respect to the use of "comprising", "including", "containing", "having" and "ensing" and the like, these terms are used in the sense of "open" terms (i.e., in the sense of "including, but not limited to").

[0071] The raw materials used in the present application are all purchased on the market.

[0072] The technical solutions of the present application are further illustrated by the following examples.

[0073] Example 1

[0074] A hydrothermal reconstruction-precise lithium supplementing process, comprising the following steps:

[0075] 1. Pretreatment

[0076] Lithium ion batteries (ternary) retired on electric vehicles are selected, and the positive electrode sheets are separated after disassembly. The positive electrode sheets are sintered at 550°C for 4 hours, ground, and passed through a 300 mesh screen to obtain D-NCM111 (n(Ni) : n(Co) : n(Mn) : n(Li) = 1 : 0.991 : 0.976 : 2.671). The purpose of this step is to remove organic binders and other impurities in the positive electrode sheets, preparing for the subsequent hydrothermal reaction.

[0077] 2. Hydrothermal reaction

[0078] 1000 mg of D-NCM111 was put into a 50 ml hydrothermal reactor, 30 ml of deionized water was added, no additional lithium source was added, and no other material was added. The reactor was in a forced air drying oven, and reacted at 200°C for 3 hours. After the reactor was cooled, the product was washed with water three times and put into a vacuum drying oven at 90°C for 10 hours to obtain the hydrothermal product (H-NCM111).

[0079] 3. Lithium supplement

[0080] The amount of substance of lithium, nickel, cobalt and manganese of the hydrothermal product (H-NCM111) was determined by ICP. According to the determination results, a certain stoichiometric ratio of lithium hydroxide monohydrate (LiOH·H2O) was added, and the n(Li) / [n(Ni)+n(Co)+n(Mn)] value of H-NCM111-Li reached 1.00, 1.05, 1.10, 1.15 respectively. Lithium hydroxide monohydrate and H-NCM111 were poured into a mortar, a little anhydrous ethanol was added, and manual grinding was started until all the anhydrous ethanol was volatilized. The lithium supplement product (H-NCM111-Li) was collected. According to the method of the present embodiment, the lithium hydroxide monohydrate consumed per 1000 mg of material (D-NCM111 material) regenerated is within 200 mg.

[0081] 4. Annealing

[0082] The lithium supplement product (H-NCM111-Li) was put into a corundum crucible and sintered in a muffle furnace, i.e. heated to 800°C at a rate of 5°C / min in an air atmosphere, kept for 5h and then cooled to room temperature with the furnace to obtain the regenerated product (R-NCM111).

[0083] Comparative Example 1

[0084] The lithium supplement was carried out by the traditional hydrothermal regeneration method, and 5000 mg or more of lithium hydroxide monohydrate (or other lithium source) was needed per 1000 mg of material (waste material from the same batch as Example 1). The lithium supplement effect of the traditional hydrothermal method is poor, because the lithium ion insertion into the crystal lattice has a large reaction barrier, and the lithium supplement is difficult.

[0085] The specific steps of the lithium supplement by the traditional hydrothermal regeneration method are as follows:

[0086] First, the failed NCM111 material (D-NCM111) was subjected to hydrothermal treatment: 1000 mg of waste NCM111 electrode material was accurately weighed and transferred to a 50 mL high-pressure reactor, 30 mL of 4 mol / L LiOH solution was added, and after sealing, it was placed in a 220°C air drying oven for 4h to complete the hydrothermal treatment;

[0087] After the hydrothermal reaction is complete, allow the reactor to cool naturally to room temperature. Remove the product and wash it repeatedly by centrifugation with deionized water until the pH of the supernatant stabilizes at 7.0±0.2 (to ensure complete removal of residual alkali from the material surface). Transfer the washed product to a 100℃ vacuum drying oven for drying.

[0088] The dried product was mixed with a certain amount of Li₂CO₃ powder (calculated according to the stoichiometric ratio of the target product, with Li element in excess by 5%, i.e., the amount of lithium carbonate added satisfies n(Li) / [n(Ni)+n(Co)+n(Mn)] reaching 1.05), and thoroughly ground in an agate mortar for 30 min until uniformly mixed. The mixture was then transferred to a corundum crucible. The crucible was placed in a tube furnace and heated to 850℃ at a rate of 5℃ / min in an oxygen atmosphere. After holding at this temperature for 4 h, it was cooled to room temperature with the furnace to finally obtain the regenerated NCM111 cathode material.

[0089] In Comparative Example 1, lithium hydroxide monohydrate at concentrations of 3 mol / L, 4 mol / L, 5 mol / L, and 0 mol / L was added to the hydrothermal reaction, respectively. After the hydrothermal reaction, the mixture was washed three times with water and dried. The resulting four groups of H-NCM111 samples were analyzed for ICP, and the lithium replenishment effect was minimal. The results are as follows: Figure 2 As shown.

[0090] Figure 2 The image shows the ICP bar charts of H-NCM111 prepared by adding 3 mol / L, 4 mol / L, 5 mol / L and 0 mol / L lithium sources to the hydrothermal reaction of Comparative Example 1, respectively. As can be seen from the figure, the lithium replenishment effect is not significantly different whether a lithium source is added or not during the hydrothermal reaction. However, D-NCM111 has a higher lithium content because there may be some lithium salt impurities on the surface of the material. After the hydrothermal reaction, these impurities are removed, resulting in a lower lithium content.

[0091] Effect verification

[0092] Excellent recovery of material structure and properties

[0093] (1) Microscopic morphology analysis

[0094] C-NCM111 (commercial material, purchased from KELU);

[0095] D-NCM111 (waste materials);

[0096] H-NCM111 (Hydrothermal material);

[0097] R-NCM111 (recycled material);

[0098] Figure 1SEM images of samples D-NCM111, H-NCM111, R-NCM111-1.10, and C-NCM111 are shown. The surface morphology and microstructure of the D-NCM111, H-NCM111, R-NCM111, and C-NCM111 samples were characterized using scanning electron microscopy (SEM), and the results are as follows. Figure 1 As shown. By Figure 1 As can be seen from (a) and (b) (SEM images of D-NCM111), although the sample still maintains a spherical outline, obvious cracks have appeared inside the particles; at the same time, the phenomenon of primary particle detachment on the surface of the spherical particles was observed, indicating that the structure and morphology of D-NCM111 have been damaged. Figure 1 Figures (c) and (d) show the SEM characterization results of H-NCM111. As can be seen from the figures, after hydrothermal treatment, the dispersibility of D-NCM111 particles is significantly improved, and impurities on the particle surface are completely eliminated. This phenomenon indicates that hydrothermal reaction can effectively dissolve lithium salt impurities on the particle surface, ensuring the smooth progress of the subsequent regeneration process. Figure 1 Images (e) and (f) show the SEM morphology characteristics of R-NCM111-1.10. After annealing, the recycled material exhibits reduced agglomeration compared to D-NCM111, with a more regular overall particle morphology and good small particle dispersion. However, compared to the commercial material C-NCM111... Figure 1 Compared to (g) and (h), the aggregate morphology shows significant differences. This may be because the waste NCM111 was originally polycrystalline; after recycling, the dense polycrystalline particles gradually become loose and pulverize, leading to the separation of some primary particles. Additionally, some primary particles that were about to separate may have already separated during the regeneration process. The figure clearly shows a significant increase in the number of small particles in the recycled material.

[0099] Figure 3 XRD patterns of C-NCM111, D-NCM111, R-NCM111-1.10, and H-NCM111; from Figure 3 As can be seen in (a), all samples exhibit a typical hexagonal α-NaFeO2 layered structure, belonging to the space point group. During the charging and discharging process of a lithium-ion battery, lithium ions shuttle between the positive and negative electrodes. During charging, lithium ions are released from the positive electrode material, leaving vacancies. Because Ni... 2+ The ionic radius (0.069 nm) of Li + The ionic radii (0.076 nm) are close to those of Ni, and under the influence of electrostatic repulsion between oxygen layers, Ni... 2+occupies the lithium site, leading to Li / Ni mixing and capacity fading. Due to Li / Ni mixing, the phase structure of the positive electrode material changes, i.e., from a layered structure to a spinel structure and a cubic rock salt phase structure, and gradually spreads from the surface to the bulk. By comparing the intensity ratio of the (003) and (104) diffraction peaks (I(003) / I(104)), the degree of lithium-nickel mixing of different materials can be preliminarily evaluated. Specifically, when I(003) / I(104) is greater than 1.20, the degree of cation mixing is low, and the electrochemical performance is good. The I(003) / I(104) value of D-NCM111 is 0.92, indicating that D-NCM111 has serious lithium-nickel mixing and a large amount of rock salt phase structure; while the I(003) / I(104) value of R-NCM111 is greater than 1.20, confirming that the degree of lithium-nickel mixing of R-NCM111 after regeneration is significantly reduced, and the rock salt phase has been restored to a layered structure.

[0100] To further analyze the restoration trend of the layered structure, the change of the (003) diffraction peak was investigated. Figure 3 (b) is the XRD pattern in the range of 18-20°, and the results show that the (003) diffraction peak of D-NCM111 shifts to the low angle direction, and the peak type presents obvious widening phenomenon, which is due to the repulsion effect between oxygen layers along the c-axis direction under the condition of lithium deficiency, resulting in the increase of the cell parameter c value. After hydrothermal reaction, the (003) diffraction peak shifts slightly to the high angle direction, but does not recover to the position of C-NCM111; after lithium supplement annealing treatment, the (003) diffraction peak of R-NCM111-1.10 recovers to the initial angle, which is completely consistent with the diffraction peak position of C-NCM111, indicating that the restoration effect of its layered structure is excellent. Previous studies have also proved that the (003) peak diffraction angle of the repaired positive electrode material recovers to the high angle.

[0101] Figure 3 (c) is the XRD pattern in the range of 64-67°, which presents the change of (108) and (110) diffraction peaks of different materials. Generally, the splitting degree of (108) / (110) diffraction peak pair is the key indicator to judge whether the material is a layered structure. The splitting phenomenon of (110) / (108) diffraction peak is related to the decrease of lattice parameter, which is due to the decrease of Ni 3+ Compared with Ni 2+ has a smaller effective ionic radius, resulting in a decrease in the average metal-metal distance, thereby leading to a decrease in the lattice parameter. After regeneration treatment, the (008) / (110) diffraction peak pair splits obviously, indicating that the crystal structure has been restored to an ordered hexagonal layered structure.

[0102] (2) Surface transition metal chemical valence state analysis

[0103] Figure 4XPS spectra of Ni, Co and Mn elements in C-NCM111, D-NCM111, R-NCM111-1.10, H-NCM111. As shown in the figure, in order to further understand the role of hydrothermal regeneration of waste ternary materials, XPS measurement is carried out to reveal the change of element valence state in NCM111, including Ni, Co, Mn elements.

[0104] As shown in Figure 4 , the XPS spectrum of Ni 2p orbit shows two main binding energy peaks and two satellite peaks. Through peak fitting analysis, it is known that the spectrum peak of Ni 2p orbit can be decomposed into Ni 3+ and Ni 2+ two chemical states, wherein Ni 3+ corresponding 2p 3 / 2 and 2p 1 / 2 orbital binding energy are located at 855.4 eV and 873.3 eV, respectively, and Ni 2+ corresponding 2p 3 / 2 and 2p 1 / 2 orbital binding energy are 854.6 eV and 871.8 eV, respectively. Quantitative analysis results show that the relative content of Ni 3+ in D-NCM111, H-NCM111, R-NCM111-1.10 and C-NCM111 is 51.35%, 55.09%, 58.66% and 59.81%, respectively, and the corresponding proportion of Ni 2+ is 48.65%, 44.91%, 41.34% and 40.19%, respectively. It is worth noting that the ratio of Ni 2+ / Ni 3+ in D-NCM111 is significantly higher than that in R-NCM111, which indicates that there is a NiO rock salt phase on the surface of D-NCM111; at the same time, this also implies that there is a more serious lithium-nickel mixing phenomenon in D-NCM111. In addition, the rock salt phase in H-NCM111 has not been completely eliminated, which may be due to the high temperature and high pressure environment of hydrothermal reaction, which can degrade part of the impurity phase in D-NCM111, but it is difficult to completely restore its structure. In sharp contrast, the ratio of Ni 3+ / Ni 2+ in R-NCM111 is basically the same as that in C-NCM111, indicating that the cation mixing degree of the regenerated ternary material is significantly improved, which has a positive significance for improving the electrochemical performance of the material.

[0105] Generally, Mn and Co elements do not participate in the redox process during the electrochemical reaction. The XPS test results further confirm this characteristic of Co element, that is, in all test materials, Co is in the form of Co 3+of other valence states were observed. However, in both D-NCM111 and H-NCM111 samples, the characteristic peak of Mn 3+ was detected, with the relative proportions of 24.8% and 17.17%, respectively. This phenomenon may be the result of the synergistic effect of material structure degradation and electrolyte side reactions during cycling. Specifically, the repeated expansion and contraction of the lattice during cycling leads to a decrease in the stability of the layered structure, while the HF and other corrosive species produced by the decomposition of the electrolyte may trigger the reduction and dissolution of Mn 4+ , ultimately contributing to the formation of Mn 3+ . The presence of Mn 3+ can significantly exacerbate the performance decline of the material: on the one hand, the Jahn-Teller effect of Mn 3+ can cause lattice distortion, hindering the diffusion dynamics of Li + ; on the other hand, compared to Mn 4+ , Mn 3+ has a stronger tendency to dissolve, which can accelerate the loss of transition metal ions, ultimately leading to continuous capacity decay and shortening of the cycle life. It is worth noting that after high-temperature annealing, the characteristic peak of Mn 3+ in the R-NCM111 sample completely disappears, indicating that the Mn element has returned to the +4 stable state, and the chemical valence characteristics of the material have returned to the level of commercial NCM111, which provides important evidence for the performance repair of the material.

[0106] (3) Electrochemical performance analysis

[0107] Pole piece preparation and battery assembly

[0108] The preparation of the test pole piece adopts the conventional proportion formula in the laboratory: the active material, polyvinylidene fluoride (PVDF), and acetylene black are weighed according to the mass ratio of 8:1:1, thoroughly mixed, uniformly coated on the surface of an aluminum foil, and then cut into circular pole pieces after vacuum drying treatment.

[0109] The assembly of the button cell is completed in an argon-filled glove box, with the humidity and oxygen content in the box strictly controlled below 0.1 ppm. CR-2032 type button half-cell structure is used, with a metal lithium sheet as the counter electrode (negative electrode) and the circular pole piece prepared above as the working electrode.

[0110] The assembled button cell is subjected to performance tests such as cycling, rate, CV, and impedance in sequence by Neware testing system.

[0111] I. Analysis of charge and discharge long cycle performance

[0112] The assembled button cells were tested by a new wei test system for electrochemical performance. The test scheme was as follows: first, 2 cycles of activation were carried out at 0.2C rate, then 100 cycles were continuously carried out at 1C rate to investigate the charge-discharge performance and cycle stability of the material. The test objects included waste NCM111 (D-NCM111), commercial NCM111 (C-NCM111) and four kinds of regenerated NCM111 with different lithium supplement amounts (labeled as R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10 and R-NCM111-1.15, respectively).

[0113] Figure 5 The electrochemical cycle performance test chart of the button cells made of C-NCM111, D-NCM111 and regenerated NCM111 with different lithium supplement amounts in Example 1 is shown in FIG. 1. Figure 5 It can be seen that the electrochemical performance of the NCM111 material after regeneration treatment is significantly improved. The specific data are as follows:

[0114] In the first circle discharge test at 1C rate, the discharge specific capacity of D-NCM111 was only 71.86mAh g -1 ; the discharge specific capacity of the regenerated materials was greatly improved, and the discharge specific capacity of R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10 and R-NCM111-1.15 was 98.33, 124.73, 138.03 and 131.77mAh g -1 ; the first circle discharge specific capacity of the commercial material C-NCM111 was 135.92mAh g -1 . The initial discharge specific capacity of R-NCM111-1.10 was nearly doubled compared with D-NCM111, and was basically the same as that of the commercial material C-NCM111.

[0115] After 100 cycles, the discharge specific capacity of D-NCM111, R-NCM111-1.00, R-NCM111-1.05, R-NCM111-1.10, R-NCM111-1.15 and C-NCM111 was 62.39, 63.42, 82.85, 131.75, 114.81 and 130.72mAh g -1 , respectively. Among them, the capacity retention rate of R-NCM111-1.10 was as high as 95.45%, which was basically the same as that of C-NCM111 (96.17%), showing excellent cycle stability.

[0116] In summary, the above test results show that the electrochemical performance of the D-NCM111 material is poor, while the specific discharge capacity and cycle stability of the four NCM111 materials prepared by the regeneration method with different lithium supplement amounts are significantly improved. Especially the regenerated material R-NCM111-1.10 with a lithium supplement amount of 1.10, its electrochemical performance is close to the level of commercial NCM111, which confirms that the regeneration method has significant effect on the repair and performance improvement of NCM111 cathode material.

[0117] II. Cyclic voltammetry analysis (CV)

[0118] Figure 6 The first three cyclic voltammetry test graphs of D-NCM111, D-NCM111 represents the waste NCM111 material, and the CV curve shows a unique electrochemical behavior characteristic. During the three cycles, the redox peaks of the first cycle are obviously offset compared with the subsequent cycles, which indicates that there are a large number of irreversible reactions in the first charge and discharge stage of the waste material, such as side reactions on the electrode surface, material structure damage due to previous use, and then interfere with the normal migration of lithium ions. Moreover, the larger peak potential difference (ΔE = 0.345 V) of the first cycle indicates that the electrode reaction polarization of the waste material is serious, and the lithium ion deintercalation process in the electrode is seriously hindered, which reflects from the side that the structure integrity of the waste material is destroyed after use, the active sites are reduced or contaminated, which greatly affects the kinetics of lithium ion intercalation and deintercalation process, leading to the decline of its electrochemical performance. The oxidation peak and the reduction peak correspond to the deintercalation and intercalation process of lithium ion respectively, and the wide peak shape and large peak potential difference of D-NCM111 fully show that the waste material has large resistance and poor reversibility in the lithium ion deintercalation reaction, and the structure disorder problems such as lattice distortion and impurity accumulation in the material, which restrict the performance of the electrochemical performance.

[0119] Figure 7The images show the cyclic voltammetry (CV) curves of R-NCM111-1.10 for the first three cycles. As a regenerated NCM111 material, R-NCM111-1.10 exhibits excellent electrochemical performance recovery. The CV curves for the first three cycles show high peak overlap and a small peak potential difference (ΔE = 0.105V) in the first cycle, strongly demonstrating a significant reduction in electrode polarization after regeneration and a substantial improvement in the reversibility of lithium-ion insertion / extraction. This indicates that the regeneration process successfully repaired the structural defects of the waste material. By reorganizing the crystal lattice, removing impurities, and supplementing active sites, lithium ions can migrate more smoothly during charge-discharge cycles, resulting in a significant improvement in electrode kinetics. The sharp and symmetrical oxidation and reduction peaks reflect that the regenerated material possesses a more ordered crystal structure and superior electrochemical activity, with low resistance and fast speed in lithium-ion insertion / extraction reactions, and stable electrochemical performance during charge-discharge processes. Compared with D-NCM111, it is clear that the regeneration process can effectively restore the electrochemical activity of NCM111 material and enhance its application potential as a cathode material for lithium-ion batteries. This indicates that the regenerated material has better reversibility and kinetic characteristics in the redox reaction of lithium-ion insertion and extraction.

[0120] III. Electrochemical Impedance Spectroscopy (EIS)

[0121] Figure 8 The figure shows the electrochemical impedance spectroscopy (EIS) spectra of three NCM111 materials (D-NCM111, R-NCM111-1.10, and C-NCM111), and the fitting results of their impedance data are shown in Table 1.

[0122] Table 1. Fitting results of impedance spectrum data

[0123] Materials Rs Rct Wo D-NCM111 3.94 71.03 72.60 R-NCM111-1.10 3.49 31.14 12.13 C-NCM111 3.48 30.85 11.75

[0124] Depend on Figure 8 As shown in Table 1, the ohmic impedance (Rs) values ​​of the three materials are relatively similar. This indicates that the systematic error has a basically consistent impact on the three materials during the selection and assembly of the coin cell, and impedance deviations caused by experimental operation or material substrate differences can be ruled out.

[0125] The analysis results of interfacial transfer resistance (Rct) show that the Rct of D-NCM111 is 71.03 Ω, which is significantly higher than those of the other two materials, which may be due to the formation of a thicker passivation layer on the surface of the waste material (D-NCM111). The passivation layer is derived from the deterioration of the material surface structure (such as changes in element valence, deposition of impurities, etc.), thereby hindering the transfer process of electric charges at the electrode / electrolyte interface. After the regeneration treatment, the Rct of R-NCM111-1.10 decreases to 31.14 Ω, which is close to that of the commercial material C-NCM111 (30.85 Ω), indicating that the regeneration process effectively repairs the defect structure on the surface of the material, and the interfacial charge transfer capacity is basically restored to the commercial level.

[0126] The change rule of diffusion migration resistance (Wo) is consistent with that of Rct: the Wo of D-NCM111 is as high as 72.60 Ω, indicating that the diffusion process of lithium ions in its bulk phase or interface is severely hindered; and the Wo of R-NCM111-1.10 decreases to 12.13 Ω, which is close to that of C-NCM111 (11.75 Ω). The larger the Wo value, the worse the lithium ion diffusion kinetics performance, and this result further confirms that the regeneration treatment significantly improves the diffusion channel of lithium ions in the material (such as eliminating lattice distortion and reducing lithium vacancy defects), greatly improves the diffusion performance and approaches the level of commercial materials.

[0127] IV. Analysis of rate performance

[0128] Figure 9 The figure shows the discharge specific capacity of D-NCM111 and R-NCM111-1.10 at different rates. The rate performance test is one of the key tests to evaluate the electrochemical performance of ternary materials. The discharge specific capacity of D-NCM111 and R-NCM111-1.10 at different rates was compared and analyzed, and the test rate range was set to 0.2-5C, and then returned to 0.2C, and each rate was tested for 5 cycles, and the results are shown in Figure 9 At test rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, the discharge capacities of R-NCM111-1.10 are 149.92 mAh g -1 , 122.21 mAh g -1 , 138.74 mAh g -1 , 131.53 mAh g -1 and 118.81 mAh g -1 , respectively. When the rate returns to 0.2C again, the discharge specific capacity can recover to 148.46 mAh g -1 , showing good capacity recovery ability and rate performance. In contrast, the rate performance of the waste ternary material is poor, and at the same rate, the discharge capacity is only 85.95 mAh g -1, 73.98 mAh g -1 , 64.27 mAh g -1 , 52.11 mAh g -1 and 34.36 mAh g -1 , 85.04 mAh g -1 In summary, the regeneration process effectively optimizes the electrochemical performance of the ternary material, and R-NCM111-1.10 exhibits better characteristics in terms of rate adaptability, capacity recovery ability and cycle stability, providing strong data support for the recycling of waste ternary materials.

[0129] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A hydrothermal reconstruction-precise lithium supplementing process, characterized in that, The method comprises the following steps: (1) sintering the positive plate in the waste battery, sieving, and obtaining D-NCM111; (2) adding water to the D-NCM111 to perform a hydrothermal reaction, and then sequentially performing water washing and drying, and obtaining H-NCM111; (3) adding a lithium source to the H-NCM111 and a solvent, and performing grinding, and obtaining H-NCM111-Li; (4) annealing the H-NCM111-Li to obtain a regenerated material R-NCM111.

2. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The sintering condition in step (1) is sintering at 550 DEG C for 4 hours.

3. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The dosage ratio of the D-NCM111 to water in step (2) is 1000-2000 mg: 30 ml.

4. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The hydrothermal reaction condition in step (2) is 200 DEG C for 3 hours.

5. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The drying condition in step (2) is 80-120 DEG C for 10 hours under vacuum.

6. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The addition amount of the lithium source in step (3) needs to meet the following condition: The ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] in the H-NCM111-Li is 1.00-1.

15.

7. The hydrothermal reconstruction-precise lithium supplementing process according to claim 6, characterized in that, The lithium source is lithium hydroxide monohydrate or lithium carbonate.

8. The hydrothermal reconstruction-precise lithium supplementing process according to claim 1, characterized in that, The annealing condition in step (4) is heating to 800 DEG C at a rate of 5 DEG C / min in an air atmosphere, keeping for 5 h, and then cooling to room temperature with the furnace.

9. A recycled material for assembling a button-type half-cell, characterized by, The regenerated material prepared by the hydrothermal reconstruction-precise lithium supplementing process according to any one of claims 1-8.

10. A button-type half cell characterized by The regenerated material according to claim 9 is used as an active material of a positive electrode.

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