A regenerated in-situ doped cathode material and a preparation method thereof

Abstract

The application discloses a preparation method of a regenerated in-situ doped positive electrode material, and comprises the following steps: (1) adding waste lithium ion battery positive electrode material into a mixed solution of 2-hydroxypropionic acid and quinic acid to perform a first reaction; (2) adding a solution of glucosamine and / or aminobutyric acid into the system after the first reaction to perform a second reaction, thereby obtaining a leaching solution rich in valuable metal ions; (3) adjusting the molar ratio of the valuable metal ions and M 2+ , adjusting the pH, and heating and evaporating and concentrating to form a gel; the ionic radius of M 2+ is 1.3-2.0 times the average ionic radius of Ni 2+ , Co 2+ , and Mn 2+ ; (4) performing step-by-step calcination on the gel to obtain a primary regenerated material doped in-situ; and (5) spraying and pyrolyzing the primary regenerated material in a surface treatment agent and then performing low-temperature heat treatment. The application further provides a regenerated in-situ doped positive electrode material.

Description

Technical Field

[0001] This application relates to the field of recycling technology for cathode materials of waste lithium-ion batteries, and in particular to a regenerated in-situ doped cathode material and its preparation method. Background Technology

[0002] Currently, researchers are dedicated to recycling and regenerating spent lithium-ion battery cathode materials to prepare new lithium-ion battery cathode materials. Existing recycling methods typically involve leaching the cathode materials with sulfuric acid and hydrogen peroxide, adjusting the pH, adding a filter aid to remove impurities, adjusting the molar ratio of nickel, cobalt, and manganese with nickel-cobalt-manganese sulfate, and then adding a complexing precipitant to react and obtain a nickel-cobalt-manganese ternary material precursor precipitate. This method requires separate separation of lithium during the precursor precipitation process, which is cumbersome and cannot effectively control the particle size and morphology of the ternary material, affecting the electrochemical performance of the final recycled material. Furthermore, since this is a secondary use of spent lithium-ion battery cathode materials, the directly recycled material still has certain differences in structure and mechanical strength compared to materials used in the conventional market due to the limitations of the recycling process, requiring further optimization to meet the requirements for secondary application.

[0003] Furthermore, although existing technologies can enhance the stability of the crystal structure in lithium-ion battery cathode materials through doping, many problems remain. On one hand, most existing doping processes employ co-precipitation to dope intercalated ions using inorganic carriers, or doping during solid-state sintering. Both methods struggle to ensure uniform distribution of dopant ions within the bulk cathode material, easily generating impurity phases during synthesis. This leads to disproportionate changes in the cell parameters of the cathode material, resulting in lattice distortion and making it difficult to guarantee the full effectiveness of the doped phase within the system. On the other hand, the selection of dopant ions and the control of the process method are also crucial. Moreover, doping alone offers limited performance improvement to cathode materials; therefore, necessary surface treatments can further enhance their mechanical strength and electrochemical performance, such as cycle life.

[0004] Therefore, in the process of recycling waste lithium-ion battery cathode materials, organically combining the regeneration process with doping modification and surface treatment processes will greatly improve the performance of recycled materials, reduce the processing cost of waste lithium-ion battery cathode materials, and will inevitably promote the development of waste lithium-ion battery cathode material regeneration technology. Summary of the Invention

[0005] To address at least one of the aforementioned problems, this application provides a simple method for preparing regenerated in-situ doped cathode materials with excellent electrochemical performance.

[0006] Another objective of this application is to provide a regenerated in-situ doped cathode material prepared by the above-described preparation method.

[0007] This application provides a method for preparing regenerated in-situ doped cathode material, comprising the following steps:

[0008] (1) Add waste lithium-ion battery cathode material to a mixed solution of 2-hydroxypropionic acid and quinic acid for the first reaction;

[0009] (2) Add a solution of glucosamine and / or gamma-aminobutyric acid to the system after the first reaction in step (1) for a second reaction, filter, and obtain a leachate rich in valuable metal ions; wherein, the valuable metal ions include Ni 2+ Co 2 + Mn 2+ and Li + ;

[0010] (3) Add divalent cation M of dopant element M to the leachate. 2+ The concentrations of each valuable metal ion and M in the leachate are adjusted according to the target product ratio. 2+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated and concentrated by evaporation to form a gel; wherein, M 2+ The ionic radius of Ni 2+ Co 2+ and Mn 2+ The average ionic radius is 1.3 to 2.0 times that of other ions;

[0011] (4) The gel is calcined in steps to obtain an in-situ doped primary regenerated material;

[0012] (5) The primary recycled material obtained in step (4) is put into a surface treatment agent for spray pyrolysis, and then subjected to low-temperature heat treatment to obtain the regenerated in-situ doped cathode material; wherein the surface treatment agent includes lithium source, niobium source and fluorine source.

[0013] This application also provides a regenerated in-situ doped cathode material prepared by the above preparation method.

[0014] Compared with the prior art, this application has the following beneficial effects:

[0015] (1) The preparation method provided in this application organically combines the recycling of valuable metal ions from waste lithium-ion batteries with the preparation of cathode materials. It adopts a one-step sol-gel method to crosslink metal ions to regenerate new layered oxides. In the regeneration process, the regenerated in-situ doped cathode material is modified by in-situ doping with divalent cations. This not only eliminates the subsequent dry doping step, shortens the process, saves costs, but also achieves doping modification of the regenerated material.

[0016] (2) Through the organic phase and dissolved nickel, cobalt, manganese, lithium, and doped ions with a radius of Ni2+ Co 2+ Mn 2+ Divalent cation M with an average ionic radius of 1.3-2.0 times 2+ Complexation is formed to create primary regenerated materials with in-situ doped divalent cations, allowing the divalent cations to be uniformly distributed in the bulk phase of the cathode material. This achieves uniform distribution of doped elements and stabilizes the material structure. The doping of these large-ionic-radius divalent cations into the ternary material lattice structure can stabilize the layered structure of the bulk phase while increasing the interlayer spacing, which is more conducive to lithium ion insertion / extraction, thereby improving the cycle stability and rate performance of lithium-ion batteries.

[0017] (3) Using a surface treatment agent to introduce lithium niobium fluorine composite by spray pyrolysis, the surface of the in-situ doped primary recycled material is coated and modified, which can reduce the direct contact between the material and air or electrolyte, reduce the absorption of H2O / CO2 by the material or the side reaction with the electrolyte, thereby improving its cycle stability and safety performance, and improving the rate performance of the material. Attached Figure Description

[0018] Figure 1 The image shows the XRD pattern of the regenerated in-situ doped cathode material prepared in Example 1.

[0019] Figure 2 The graph shows the cycling curves of the lithium-ion batteries prepared in Example 1 and Comparative Examples 1-3 at 0.5C rate and 45°C. Detailed Implementation

[0020] The present application is further illustrated below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on this application are within the scope of protection claimed in this application.

[0021] One embodiment of this application provides a method for preparing a regenerated in-situ doped cathode material, comprising the following steps:

[0022] (1) Add waste lithium-ion battery cathode material to a mixed solution of 2-hydroxypropionic acid and quinic acid for the first reaction;

[0023] (2) Add a solution of glucosamine and / or gamma-aminobutyric acid to the system after the first reaction in step (1) for a second reaction, filter, and obtain a leachate rich in valuable metal ions; wherein, the valuable metal ions include Ni 2+ Co2 + Mn 2+ and Li + ;

[0024] (3) Add divalent cation M of dopant element M to the leachate. 2+ The concentrations of each valuable metal ion and M in the leachate are adjusted according to the target product ratio. 2+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated and concentrated by evaporation to form a gel; wherein, M 2+ The ionic radius of Ni 2+ Co 2+ and Mn 2+ The average ionic radius is 1.3 to 2.0 times that of other ions;

[0025] (4) The gel is calcined in steps to obtain an in-situ doped primary regenerated material;

[0026] (5) The primary recycled material obtained in step (4) is put into a surface treatment agent for spray pyrolysis, and then subjected to low-temperature heat treatment to obtain the regenerated in-situ doped cathode material; wherein the surface treatment agent includes lithium source, niobium source and fluorine source.

[0027] Compared with existing technologies, the preparation method provided in this application organically combines the recycling of valuable metals from waste lithium-ion batteries with the preparation of cathode materials. It adopts a one-step sol-gel method to crosslink metal ions to regenerate new layered oxides. In the regeneration process, the regenerated in-situ doped cathode material is modified by in-situ doping with divalent cations. This not only eliminates the subsequent dry doping step, shortens the process, saves costs, but also achieves doping modification of the regenerated material.

[0028] Furthermore, through the organic phase and dissolved nickel, cobalt, manganese, lithium, and doped ions with a radius of Ni 2+ Co 2+ Mn 2+ Divalent cation M with an average ionic radius of 1.3-2.0 times 2+ Complexation is formed to create primary regenerated materials with in-situ doped divalent cations, allowing the divalent cations to be uniformly distributed in the bulk phase of the cathode material. This achieves uniform distribution of doped elements and stabilizes the material structure. The doping of these large-ionic-radius divalent cations into the ternary material lattice structure can stabilize the layered structure of the bulk phase while increasing the interlayer spacing, which is more conducive to lithium ion insertion / extraction, thereby improving the cycle stability and rate performance of lithium-ion batteries.

[0029] Furthermore, by employing a two-step leaching method involving pre-acidification with organic acids (2-hydroxypropionic acid and quinic acid) and continuous reduction with organic reducing agents (glucosamine and / or gamma-aminobutyric acid), this method fully utilizes the acidity and chelating properties of organic acids and the reducing and chelating properties of organic reducing agents. This avoids problems such as partial loss of reducing power and insufficient utilization of reducing power caused by the one-time addition of organic reducing agents. It enables the recycling of valuable metal elements in waste lithium-ion battery cathode materials, recovering a high-purity leachate rich in valuable metals. The leaching process is gentle and controllable, with a short heating residence time, ultimately achieving a high leaching rate with low energy consumption. Research has found that compared to a one-step leaching method using both organic acids and organic reducing agents, the two-step leaching method in this application has higher leaching efficiency. Under a certain solid-liquid ratio, the two-step leaching method produces almost no filter residue, allowing complete dissolution of the waste lithium-ion battery cathode material. In contrast, the one-step leaching method has lower efficiency and produces more undissolved filter residue. Since the various valuable metal ions and M in the leachate need to be adjusted during subsequent regeneration processes... 2+ With a certain molar ratio, one-step leaching inevitably requires the addition of more soluble salts to compensate for the loss of undissolved filter cake.

[0030] In addition, by using a surface treatment agent and spraying pyrolysis to introduce a lithium-niobium-fluorine complex, the surface of the in-situ doped primary recycled material is modified by coating. Taking advantage of the high activity of niobium acetate, it reacts with lithium source and trifluoroacetic acid to coat the material surface with a layer of metal fluoride. This reduces the direct contact between the material and air or electrolyte, reduces the absorption of H2O / CO2 by the material or the side reaction with the electrolyte, thereby improving its cycle stability and safety performance, and improving the rate performance of the material.

[0031] In some embodiments, the chemical formula of the regenerated in-situ doped cathode material is Li. k Ni x Co y Mn z M m O2·nLiNbF6, wherein x:y:z:m=(0.10~0.85):(0.05~0.40):(0.10~0.35):(0.001~0.1), and x+y+z+m=1, 0.95≤k≤1.15, 0<n≤0.05; the doping element M is at least one of Ca, Sr, Ba or Cd.

[0032] In some embodiments, the general chemical formula of the waste lithium-ion battery cathode material mentioned in step (1) is LiNi. x Co y Mn z O2, where x:y:z = (0~1):(0~1):(0~1), and x, y, and z are not all 0 at the same time.

[0033] In some embodiments, the ratio of the total mass of the 2-hydroxypropionic acid and quinic acid to the mass of the waste lithium-ion battery cathode material is (5-50):(50-95). The temperature of the first reaction is 30-70°C, the time is 0.1-1 h, and the stirring speed is 200-600 r / min.

[0034] In some embodiments, the mass ratio of the glucosamine and / or gamma-butyric acid to the mass of the waste lithium-ion battery cathode material is 5-500:1000. The second reaction is carried out at a temperature of 30-60°C for 0.1-1 h, and at a stirring speed of 300-600 r / min.

[0035] In step (3), the content of each valuable metal ion in the leachate can be detected by conventional detection methods such as atomic emission spectrometry (ICP). Then, by adding the corresponding metal element and the salt of dopant element M, the proportion of each metal element in the leachate can be adjusted to the target ratio. Performing two ICP tests on the leachate before and after the test can determine whether the proportion of each metal ion meets the design requirements.

[0036] The salts of the corresponding metal element and the dopant element M can be any salts soluble in this leaching solution system, such as nickel acetate, cobalt acetate, manganese acetate, lithium acetate, strontium acetate, etc.

[0037] In step (3), the pH is adjusted to 6.5 to 7.5, and the heating temperature is 40 to 90°C. The reagent for adjusting the pH is one or more of ammonia, ammonium acetate, and ammonium citrate.

[0038] The stepwise calcination in step (4) includes calcining the gel in at least two steps under an oxygen or air atmosphere.

[0039] In some embodiments, the temperature of the first calcination step is 100–400°C, the residence time is 2–15 h, and the heating rate is 1–10°C / min; the temperature of the second calcination step is 450–900°C, the residence time is 1–12 h, and the heating rate is 1–20°C / min.

[0040] The equipment for step-by-step calcination includes one of the following: rotary kiln, tube furnace, box furnace, bell furnace, or roller kiln.

[0041] In some embodiments, the lithium source in step (5) is one or more of lithium ethoxide, lithium methyl, and n-butyllithium; the fluorine source is trifluoroacetic acid; the niobium source is niobium ethoxide; and the solvent is ethylene glycol. The amounts of the lithium source, fluorine source, and niobium source can be reasonably set according to the molar proportions in the target product.

[0042] In some embodiments, the temperature of the spray pyrolysis in step (5) is 100 to 300°C.

[0043] The low-temperature heat treatment process described in this application is an annealing process, and the total annealing time is 4 to 8 hours. The annealing process includes two stages: the temperature of the first stage is 500 to 700°C, and the temperature of the second stage is 300 to 450°C. The time of the first stage is 1 / 5 to 1 / 3 of the time of the second stage.

[0044] This application employs a sol-gel method combined with stepwise calcination and spray pyrolysis to prepare regenerated in-situ doped cathode materials. The first calcination step, performed at a relatively low temperature, thoroughly removes organic matter or organic carbon chains from the sol-gel process, preparing the material for the next crystallization step. The second calcination step, performed at a higher temperature, is the process of material crystallization, i.e., the construction of the material structure. The material prepared in this step is essentially at an applicable level. If stepwise calcination is not used, insufficient removal of organic matter or organic carbon chains may occur, leading to rapid material crystallization and residual organic impurities, which severely affect performance.

[0045] In some embodiments, a third calcination step can be performed after spray pyrolysis, which can optimize the structure of the regenerated in-situ doped cathode material and promote the formation of the surface coating layer after surface treatment.

[0046] This application also provides a regenerated in-situ doped cathode material prepared by the above preparation method.

[0047] The preparation method and performance of the regenerated in-situ doped cathode material are described below using specific examples and comparative examples.

[0048] Example 1

[0049] This embodiment provides a method for preparing a regenerated in-situ doped cathode material. The chemical formula of the regenerated in-situ doped cathode material to be prepared is LiNi. 0.698 Co 0.1 Mn 0.197 M 0.005 O2·0.002LiNbF6, where M is Sr. The preparation method specifically includes the following steps:

[0050] (1) Add 55g of 2-hydroxypropionic acid and 2g of quinic acid to 3L of deionized water to prepare a mixed solution. 500g of LiNi... 0.55 Co 0.2 Mn 0.25 O2 was added to the above mixed solution to carry out the first reaction. The reaction temperature was 60℃, the reaction time was 0.2h, and the stirring speed was 300r / min.

[0051] (2) Add 20g of glucosamine and 1g of gamma-aminobutyric acid to 4.8L of deionized water to prepare a mixed solution. Slowly pump the above mixed solution into the system after the reaction in step (1) at a flow rate of 4.8L / h to carry out a second reaction. The reaction temperature is 45℃ and the stirring speed is 350r / min. After 1h, the pumping is stopped, and a black turbid liquid is obtained. Filter the black turbid liquid to remove the filter residue, and a leachate rich in valuable metal ions is obtained.

[0052] (3) Add divalent cation M of dopant element M to the leachate from step (2). 2+ (i.e., Sr) 2+ ), and adjust Ni 2+ Co 2+ Mn 2+ 、Sr 2+ Li + The molar ratio x:y:z:m:k satisfies x:y:z:m=0.698:0.1:0.197:0.005, k=1.08, and ammonium acetate solution is added to adjust the pH to 7.1. Most of the water is removed by heating at 50℃ to form a gel.

[0053] (4) The above gel was transferred to a roller kiln and calcined in a stepwise manner under an oxygen atmosphere. The first calcination temperature was 250℃, the residence time was 3h, and the heating rate was 5℃ / min; the second calcination temperature was 800℃, the residence time was 10h, and the heating rate was 10℃ / min. After sieving, the calcined material was obtained as in-situ doped Sr. 2+ Primary recycled materials.

[0054] (5) Based on the stoichiometry in the target product, the in-situ doped Sr obtained in step (4) is... 2+ The primary recycled material is added to an ethylene glycol solution containing a specific molar amount of methyl lithium, trifluoroacetic acid, and niobium ethanol, and sprayed pyrolysis is performed at 200°C. The product after spray pyrolysis is then annealed under a nitrogen atmosphere, held at 680°C for 1.5 hours, cooled to 330°C, and held for another 5 hours to obtain the regenerated in-situ doped cathode material.

[0055] Figure 1 The image shows the XRD pattern of the regenerated in-situ doped cathode material prepared in Example 1. As can be seen from the image, the regenerated in-situ doped cathode material prepared in this example is LiNi. 0.698 Co 0.1 Mn 0.197 Sr 0.005The diffraction peaks of O2·0.002LiNbF6 are sharp, indicating high crystallinity and the absence of impurity peaks. The main peaks conform to the layered structure of nickel-cobalt-manganese oxides, indicating that the doping elements have been fully incorporated into the lattice structure of the cathode material and have not formed compounds separately outside the main structure of the nickel-cobalt-manganese cathode material.

[0056] Example 2

[0057] This embodiment provides a method for preparing a regenerated in-situ doped cathode material. The chemical formula of the regenerated in-situ doped cathode material to be prepared is LiNi. 0.497 Co 0.198 Mn 0.297 M 0.008 O2·0.005LiNbF6, where M is Ba. The preparation method specifically includes the following steps:

[0058] (1) Add 100g of 2-hydroxypropionic acid and 5g of quinic acid to 6L of deionized water to prepare a mixed solution. 1000g of LiNi 0.33 Co 0.33 Mn 0.33 O2 was added to the above mixed solution to carry out the first reaction. The reaction temperature was 57℃, the reaction time was 0.2h, and the stirring speed was 310r / min.

[0059] (2) Add 40g of glucosamine and 2g of gamma-aminobutyric acid to 10L of deionized water to prepare a mixed solution. Slowly pump the above mixed solution into the system after the reaction in step (1) at a flow rate of 10L / h to carry out a second reaction. The reaction temperature is 49℃ and the stirring speed is 380r / min. After 1h, the pumping is stopped, and a black turbid liquid is obtained. Filter the black turbid liquid to remove the filter residue, and a leachate rich in valuable metal ions is obtained.

[0060] (3) Add divalent cation M of dopant element M to the leachate from step (2). 2+ (i.e. Ba 2+ ), and adjust Ni 2+ Co 2+ Mn 2+ Ba 2+ Li + The molar ratio x:y:z:m:k satisfies x:y:z:m=0.497:0.198:0.297:0.008, k=1.08, and ammonium citrate solution is added to adjust the pH to 7.0. Most of the water is removed by heating at 55℃ to form a gel.

[0061] (4) The above gel was transferred to a roller kiln and calcined in a stepwise manner under an oxygen atmosphere. The first calcination temperature was 300℃, the residence time was 3h, and the heating rate was 5℃ / min; the second calcination temperature was 830℃, the residence time was 11h, and the heating rate was 10℃ / min. After sieving, the calcined material was obtained as in-situ doped Ba. 2+ Primary recycled materials.

[0062] (5) Based on the stoichiometry in the target product, the in-situ doped Ba obtained in step (4) is... 2+ The primary recycled material is added to an ethylene glycol solution containing specific molar amounts of n-butyllithium, trifluoroacetic acid, and niobium ethanol, and sprayed pyrolysis is performed at 220°C. The product after spray pyrolysis is then annealed under a nitrogen atmosphere, held at 580°C for 2 hours, cooled to 330°C, and held for another 5 hours to obtain the regenerated in-situ doped cathode material.

[0063] Example 3

[0064] This embodiment provides a method for preparing a regenerated in-situ doped cathode material. The chemical formula of the regenerated in-situ doped cathode material to be prepared is LiNi. 0.599 Co 0.198 Mn 0.197 M 0.006 O2·0.006LiNbF6, where M is Ca. The preparation method specifically includes the following steps:

[0065] (1) Add 100g of 2-hydroxypropionic acid and 5g of quinic acid to 6L of deionized water to prepare a mixed solution. 1000g of LiNi 0.33 Co 0.33 Mn 0.33 O2 was added to the above mixed solution to carry out the first reaction. The reaction temperature was 57℃, the reaction time was 0.2h, and the stirring speed was 310r / min.

[0066] (2) Add 45g of GABA to 10L of deionized water to prepare a mixed solution. Slowly pump the mixed solution into the system after the reaction in step (1) at a flow rate of 10L / h to carry out a second reaction. The reaction temperature is 49℃, the stirring speed is 380r / min, and the pumping is stopped after 1h, resulting in a black turbid liquid. Filter the black turbid liquid to remove the filter residue, and obtain a leachate rich in valuable metal ions.

[0067] (3) Add divalent cation M of dopant element M to the leachate from step (2). 2+ (i.e. Ca) 2+ ), and adjust Ni 2+ Co2+ Mn 2+ Ca 2+ Li + The molar ratio x:y:z:m:k satisfies x:y:z:m=0.599:0.198:0.197:0.006, k=1.08, and ammonium citrate solution is added to adjust the pH to 7.0. Most of the water is removed by heating at 55℃ to form a gel.

[0068] (4) The above gel was transferred to a roller kiln and calcined in a stepwise manner under an oxygen atmosphere. The first calcination temperature was 300℃, the residence time was 3h, and the heating rate was 5℃ / min; the second calcination temperature was 830℃, the residence time was 11h, and the heating rate was 10℃ / min. After sieving, the calcined material was obtained as in-situ doped Ca. 2+ Primary recycled materials.

[0069] (5) Based on the stoichiometry in the target product, the in-situ doped Ba obtained in step (4) is... 2+ The primary recycled material is added to an ethylene glycol solution containing specific molar amounts of lithium ethanol, trifluoroacetic acid, and niobium ethanol, and sprayed at 180°C for pyrolysis. The product after spraying pyrolysis is then annealed under a nitrogen atmosphere, held at 550°C for 2 hours, cooled to 350°C, and held for another 5 hours to obtain the regenerated in-situ doped cathode material.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that no in-situ doping with divalent cations is performed. The chemical formula of the regenerated in-situ doped cathode material prepared is LiNi. 0.70 Co 0.10 Mn 0.30 O2·0.002LiNbF6. That is, adjusting Ni in step (3). 2+ Co 2+ Mn 2+ Li + The molar ratios x:y:z:k satisfy x:y:z=0.70:0.10:0.30, k=1.08.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that step (5) is omitted, and the chemical formula of the regenerated in-situ doped cathode material prepared is LiNi. 0.698 Co 0.1 Mn 0.197 Sr 0.005 O2.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that the waste lithium-ion battery cathode material is simultaneously added to a mixed solution of 2-hydroxypropionic acid, quinic acid, glucosamine, and gamma-aminobutyric acid during the leaching process. That is, steps (1) and (2) are combined into one step.

[0076] 55g of 2-hydroxypropionic acid, 2g of quinic acid, 20g of glucosamine, and 1g of gamma-aminobutyric acid were added to 7.8L of deionized water to prepare a mixed solution. 500g of LiNi... 0.55 Co 0.2 Mn 0.25 O2-containing waste lithium-ion battery cathode material was added to the above mixed solution and reacted at a temperature of 60°C for 1.2 hours with a stirring speed of 300 r / min, resulting in a black turbid liquid. The black turbid liquid was then filtered to remove the filter residue, yielding a leachate rich in valuable metal ions.

[0077] The other steps are the same as in Example 1, and the chemical formula of the prepared regenerated in-situ doped cathode material is LiNi. 0.698 Co 0.10 Mn 0.197 Sr 0.005 O2·0.002LiNbF6.

[0078] The study found that the black turbid liquid obtained in Comparative Example 3 contained more filter residue, indicating that a significant amount of waste lithium-ion battery cathode material remained undissolved, and the mass of the filter residue was 20 to 50 times that of Example 1.

[0079] The regenerated in-situ doped cathode materials prepared in Example 1 and Comparative Examples 1-3 were subjected to a 50 MPa compaction test to measure the change in the median particle size D50 of the materials before and after compaction, thereby evaluating the mechanical strength of the materials. The test results are shown in Table 1.

[0080] Table 1. Mechanical strength test results of materials prepared in Example 1 and Comparative Examples 1-3

[0081] Example 1 4.18 4.09 2.2 Comparative Example 1 4.11 3.9 5.1 Comparative Example 2 4.25 3.91 8.0 Comparative Example 3 4.15 3.94 5.1

[0082] As shown in Table 1, the regenerated in-situ doped cathode material prepared in Example 1 of this application has a lower D50 loss rate before and after compaction. Compared with the regenerated in-situ doped cathode materials prepared in Comparative Examples 1-3, Example 1 has a lower D50 loss rate before and after compaction and higher mechanical strength.

[0083] The regenerated positive electrode materials prepared in Example 1 and Comparative Examples 1-3 were respectively added to acetylene black and polyvinylidene fluoride (PVDF), mixed evenly, and then ground into a uniform slurry. The slurry was coated onto aluminum foil to form a positive electrode. A coin cell was made using lithium metal sheet as the negative electrode and LiPF6 as the electrolyte. The electrochemical test voltage was 4.3V.

[0084] Figure 2 The graphs show the cycling curves of the lithium-ion batteries prepared in Example 1 and Comparative Examples 1-3 at 0.5C rate and 45°C. Figure 2 As can be seen, the lithium-ion battery prepared in Example 1 has an initial discharge specific capacity of 209.6 mAh / g, and after 50 cycles, the discharge specific capacity is still as high as 204.9 mAh / g, with a capacity retention rate of 97.8%. However, the lithium-ion battery prepared in Comparative Example 1 has a capacity retention rate of only 93.4%, the material capacity retention rate in Comparative Example 2 is only 95.8%, and the initial discharge specific capacity of the lithium-ion battery prepared in Comparative Example 3 is only 198.9 mAh / g.

[0085] In summary, this application organically combines the recycling of valuable metals from spent lithium-ion batteries with the preparation of cathode materials. A one-step sol-gel method is used to crosslink metal ions to regenerate new cathode materials. During the regeneration process, the regenerated material undergoes in-situ doping modification with large-radius divalent cations, ensuring uniform distribution of the doped divalent cations within the bulk phase of the cathode material. This achieves atomic-level homogeneous mixing, increases interlayer spacing, and is more conducive to lithium-ion insertion / extraction. The resulting regenerated in-situ doped cathode material exhibits high crystallinity, uniform doping, absence of impurity phases, and high mechanical strength, thus possessing excellent electrochemical performance.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing a regenerated in-situ doped cathode material, characterized in that, Includes the following steps: (1) The waste lithium-ion battery cathode material is added to a mixed solution of 2-hydroxypropionic acid and quinic acid for the first reaction; the ratio of the total mass of the 2-hydroxypropionic acid and quinic acid to the mass of the waste lithium-ion battery cathode material is (5-50):(50-95). (2) Add a solution of glucosamine and / or gamma-aminobutyric acid to the system after the first reaction in step (1) for a second reaction, filter, and obtain a leachate rich in valuable metal ions; wherein, the valuable metal ions include Ni 2+ Co 2+ Mn 2 + and Li + The mass ratio of glucosamine and / or gamma-aminobutyric acid to the mass of the waste lithium-ion battery cathode material is 5~500:1000. (3) Add divalent cation M of dopant element M to the leachate. 2+ The concentrations of each valuable metal ion and M in the leachate are adjusted according to the target product ratio. 2+ The molar ratio is adjusted, pH is adjusted, and the mixture is heated and concentrated by evaporation to form a gel; wherein, M 2+ The ionic radius of Ni 2+ Co 2+ and Mn 2+ The average ionic radius is 1.3 to 2.0 times that of other ions; (4) The gel is calcined in stages to obtain in-situ doped primary regenerated material; (5) The primary recycled material obtained in step (4) is put into a surface treatment agent for spray pyrolysis, and then subjected to low-temperature heat treatment to obtain the regenerated in-situ doped cathode material; wherein the surface treatment agent includes a lithium source, a niobium source and a fluorine source. The chemical formula of the regenerated in-situ doped cathode material is Li. k Ni x Co y Mn z M m O2·nLiNbF6, wherein x:y:z:m =(0.10~0.85):(0.05~0.40):(0.10~0.35):(0.001~0.1), and x+y+z+m=1, 0.95≤k≤1.15, 0<n≤0.05; the doping element M is at least one of Ca, Sr, Ba or Cd.

2. The preparation method according to claim 1, characterized in that, The general chemical formula of the waste lithium-ion battery cathode material mentioned in step (1) is LiNi. x Co y Mn z O2, where x:y:z=(0~1):(0~1):(0~1), and x, y, and z are not all 0 at the same time.

3. The preparation method according to claim 1, characterized in that, The temperature of the first reaction is 30-70℃, the time is 0.1-1h, and the stirring speed is 200-600r / min.

4. The preparation method according to claim 1, characterized in that, The second reaction is carried out at a temperature of 30-60℃ for 0.1-1h, with a stirring speed of 300-600r / min.

5. The preparation method according to claim 1, characterized in that, In step (3), the pH is adjusted to 6.5~7.5, and the heating temperature is 40~90℃; the reagent for adjusting the pH is one or more of ammonia, ammonium acetate, and ammonium citrate.

6. The preparation method according to claim 1, characterized in that, The stepwise calcination in step (4) includes: calcining the gel in at least two steps under an oxygen or air atmosphere; The first calcination step involves a temperature of 100-400℃, a residence time of 2-15h, and a heating rate of 1-10℃ / min. The second calcination step involves a temperature of 450-900℃, a residence time of 1-12h, and a heating rate of 1-20℃ / min.

7. The preparation method according to claim 1, characterized in that, The lithium source in step (5) is one or more of lithium ethanol, lithium methyl and lithium n-butyl, the fluorine source is trifluoroacetic acid, the niobium source is niobium ethanol, and the solvent is ethylene glycol.

8. The preparation method according to claim 1, characterized in that, The spray pyrolysis temperature in step (5) is 100~300℃; The low-temperature heat treatment process is an annealing process, and the total annealing time is 4~8 hours; The annealing process includes two stages: the temperature of the first stage is 500~700℃, the temperature of the second stage is 300~450℃, and the time of the first stage is 1 / 5~1 / 3 of the time of the second stage.

9. A regenerated in-situ doped cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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