A method for regenerating positive electrode materials of waste lithium-ion batteries and its application

Abstract

The present invention provides a method for regenerating waste lithium-ion battery positive electrode materials and its application, and relates to the field of lithium-ion batteries. The present invention realizes effective lithium replenishment through processes such as discharge, pyrolysis, lithium replenishment, and regeneration, by configuring a lithium replenisher containing lithium salts, lithium hydroxide, trace additives, and organic solvents, and cooperating with vacuum and high-pressure lithium replenishment technology; a specific calcination and regeneration procedure is set, calcining at low temperature first, and then calcining at high temperature, thereby forming a structure with disordered bulk doping and surface coating, and effectively realizing the recovery and regeneration of lithium-ion battery positive electrode materials. The regenerated positive electrode material obtained by the present invention can show high capacity and good high-rate cycle stability under high pressure.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a method for regenerating anode materials of waste lithium ion batteries and an application thereof. Background Art

[0002] From the perspective of resource recovery and environmental protection, it is of great significance to regenerate waste lithium-ion positive electrode materials into positive electrode materials with good performance.

[0003] At present, the regeneration methods of waste lithium-ion battery cathode materials mainly include direct regeneration method, pyrolysis method and wet method. Direct regeneration method is recognized as a relatively green and sustainable recycling method. This method is to restore the electrochemical performance of waste cathode materials by supplementing the missing elements (generally lithium) and repairing the structural defects without destroying the structure of the waste cathode materials. Compared with pyrolysis method and wet method, the whole process of direct regeneration method is green and simple, and has great potential.

[0004] However, there are still great challenges in the lithium replenishment technology in the direct regeneration method. For example, high-temperature lithium replenishment, hydrothermal lithium replenishment, molten salt lithium replenishment, electrochemical lithium replenishment and other methods have high energy consumption and cost, and the transmission kinetics of lithium are low, resulting in poor lithium replenishment effect. How to direct the short lithium elements to the defects of the cathode materials of waste lithium-ion batteries and improve the transmission kinetics of lithium elements in the waste cathode materials are the difficulties that need to be solved at present.

[0005] At the same time, improving the structural stability of recycled positive electrode materials under high voltage so that they can exert greater capacity and high-rate charge and discharge stability under high voltage is both a market demand and a frontier hotspot in the research of positive electrode materials for waste lithium-ion batteries.

[0006] A journal article entitled Adaptable Eutectic Salt for the Direct Recycling of Highly Degraded Layer Cathodes (Jun Ma et al., J. Am. Chem. Soc., 2022, Vol. 144, pp. 20306-20314) discloses a method for preparing high-voltage positive electrode materials from waste lithium-ion battery positive electrode materials, which includes discharge, positive electrode sheet separation, removal of electrolyte and additives, lithium supplementation and doping, calcination and repair, etc. The high-voltage positive electrode material obtained by this method has high capacity under high voltage and good cycle stability at 0.5C rate, with a capacity retention rate of 70% after 300 cycles. The article does not explore the cycle stability of high-voltage positive electrode materials at high rates. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the primary purpose of the present invention is to provide a method for regenerating the positive electrode material of waste lithium-ion batteries.

[0008] Another object of the present invention is to provide an application of the above regeneration method in recycling waste lithium-ion batteries.

[0009] Another object of the present invention is to provide a positive electrode material for a lithium ion battery.

[0010] Another object of the present invention is to provide a lithium ion battery.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention provides a method for regenerating anode materials of waste lithium-ion batteries, comprising the following steps:

[0013] S1. Discharge: Discharge the waste lithium-ion battery completely and disassemble it to obtain the positive electrode sheet;

[0014] S2, pyrolysis: pyrolyze the positive electrode sheet in an oxygen-containing atmosphere, the pyrolysis temperature is ≥350°C, the pyrolysis time is 0.5-3h, crush and sieve to obtain positive electrode black powder; the sieving adopts a 200-300 mesh sieve;

[0015] S3, lithium replenishment: the positive electrode black powder and the lithium replenishing agent are mixed, vacuumed, the ultimate pressure is 0.1-2Pa, and the vacuum is maintained for 5-30min; the vacuum is stopped, and then heated, the heating temperature is 60-150°C, and the heating is maintained for 20-60min to obtain the lithium replenishing positive electrode black powder;

[0016] The lithium supplement agent is a mixture of lithium salt, lithium hydroxide, trace additives and organic solvents, the trace additives are selected from at least one of aluminum compounds, magnesium compounds or titanium compounds, the molar ratio of the lithium salt to the lithium hydroxide is (1-3):1, the amount of the trace additive added does not exceed 2-4% of the total mass of the positive electrode black powder, and the boiling point of the organic solvent is lower than 150°C;

[0017] S4, regeneration: the lithium-supplemented positive electrode black powder is heated to 200-700°C for the first time in an air atmosphere at a heating rate of 2-5°C / min, and maintained for 10-20 hours, and then heated to 800-1100°C for a second time in an oxygen atmosphere at a heating rate of 10-40°C / min, and maintained for 2-6 hours to obtain a regenerated positive electrode material.

[0018] The present invention provides a method for regenerating waste lithium-ion battery positive electrode materials, and through processes such as discharge, pyrolysis, lithium supplementation, and regeneration, a regenerated positive electrode material with high capacity and good high-rate cycle stability under high pressure is obtained.

[0019] The present invention pyrolyzes the positive electrode sheet at a specific temperature in an oxygen-containing atmosphere. On the one hand, impurities such as electrolyte, binder, and conductive agent can be pyrolyzed at high temperature. On the other hand, the positive electrode material after pyrolysis can produce more pores, which is beneficial to lithium replenishment. Among them, the pyrolysis temperature needs to be controlled within a certain range. If the pyrolysis temperature is too low, on the one hand, the positive electrode black powder obtained after pyrolysis does not have sufficient pores, and on the other hand, it will lead to incomplete removal of impurities, thereby affecting the battery performance of the final regenerated positive electrode material. The particles obtained after pyrolysis and crushing contain current collector powder and positive electrode material. The present invention uses a sieve with a certain mesh number to screen out the current collector powder. If the mesh number of the sieve is too small, the current collector will be mixed into the material, affecting the material performance; if the mesh number of the sieve is too large, the screening time will be too long, and the amount of positive electrode material screened out will also be small.

[0020] For lithium replenishment technology, the present invention configures a specific lithium replenisher through lithium salt, lithium hydroxide, trace additives and organic solvents on the one hand, and uses vacuum post-high pressure lithium replenishment technology for lithium replenishment on the other hand, which can effectively improve the efficiency of lithium replenishment and improve the performance of the positive electrode material after regeneration. For the lithium replenisher, firstly, lithium salt and lithium hydroxide can be used as lithium sources to replenish lithium for the positive electrode material on the one hand, and on the other hand, the two can form a low eutectic solvent, which can form a liquid at a lower temperature under vacuum conditions, promoting the diffusion of lithium ions and trace additives; the addition of trace additives can produce a small amount of short-range disordered structure inside the positive electrode material; the organic solvent with a low boiling point can boil after heating, forming a high pressure in the system, which is conducive to lithium replenishment. For lithium replenishment technology, the present invention first evacuates the mixture of the positive electrode material and the lithium replenisher to extract the gas in the voids of the positive electrode material, and heats the mixture after stopping the vacuum. The organic solvent in the lithium replenisher boils and volatilizes with the increase of temperature, forming a high pressure in the system, and the lithium replenisher is pressed into the voids of the positive electrode material under high pressure, shortening the diffusion of lithium ions and improving the efficiency of lithium replenishment.

[0021] After the positive electrode material is supplemented with lithium, the present invention regenerates the positive electrode material by roasting to obtain a regenerated positive electrode material with short-range disorder in the bulk phase and trace elements coated on the surface. The present invention first performs calcination in an air atmosphere at a relatively low temperature so that trace additives occupy lithium positions inside the positive electrode material and introduce a chemical short-range disordered structure. Subsequently, the positive electrode material is calcined in an oxygen atmosphere at a high temperature, and the lattice inside the positive electrode material gradually develops toward order, obtaining an ordered structure of the main body. Among them, the first heating rate, the low-temperature calcination time, the second heating rate and the high-temperature calcination time all need to be controlled within a reasonable range. If the first heating rate is too fast and the low-temperature calcination time is too short, it will affect the formation of the short-range disordered structure. If the second heating rate is too slow and the high-temperature calcination time is too long, the short-range disordered structure will be ordered, which will ultimately affect the performance of the regenerated positive electrode material.

[0022] Specifically, the cathode material of the waste lithium-ion battery includes lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium-rich lithium manganese oxide. The regeneration method of the present invention is applicable to cathode materials of lithium-ion batteries of various compositions.

[0023] Preferably, S1 comprises the following steps: covering the waste lithium-ion battery with a conductive medium, discharging it to a voltage of 2.0-3.0 V, then immersing the waste lithium-ion battery with 1-3 mol / L lithium salt, completely discharging it, and disassembling it to obtain a positive electrode sheet.

[0024] Specifically, the conductive medium is selected from at least one of copper powder, aluminum powder or graphite powder; and the lithium salt is selected from at least one of lithium chloride or lithium sulfate.

[0025] In this field, physical discharge or chemical discharge is often used to discharge waste lithium-ion batteries. The physical discharge has a fast discharge speed, but there are voltage rebound and local overheating that lead to pole burning. Chemical discharge often uses a high-concentration salt solution, has a long discharge time, is easy to introduce other metal ions, and produces toxic and harmful gases. The present invention adopts a physical-chemical combined discharge method, first physically discharges to a voltage of 2.0-3.0V, and then uses a low-concentration lithium salt to perform chemical discharge until the discharge is complete, which can avoid false discharge and pole melting of waste lithium-ion batteries, shorten the discharge time, and reduce the pollution of other metal ions.

[0026] Preferably, the pyrolysis temperature in S1 is 350-550° C. A pyrolysis temperature below 550° C. can achieve good porosity and impurity removal effects.

[0027] Specifically, the oxygen-containing atmosphere in S2 is selected from at least one of an air atmosphere and an oxygen atmosphere.

[0028] Preferably, the vacuum holding time in S3 is 10 to 15 minutes.

[0029] Specifically, the lithium salt in S3 is selected from at least one of lithium fluoride, lithium chloride, lithium iodide or lithium sulfate.

[0030] Preferably, the molar ratio of the lithium salt to the lithium hydroxide in S3 is 1: 1. When the molar ratio of the lithium salt to the lithium hydroxide is 1: 1, the obtained low eutectic solvent has the lowest melting point.

[0031] Specifically, the aluminum compound in S3 is selected from at least one of aluminum chloride, aluminum oxide or aluminum hydroxide; the magnesium compound is selected from at least one of magnesium chloride, magnesium oxide or magnesium sulfate; and the titanium compound is selected from at least one of titanium oxide or titanium trioxide.

[0032] Specifically, the organic solvent in S3 is selected from at least one of methanol, ethanol, propanol, butanol, pentanol or acetone. The volume of the organic solvent used is sufficient as long as it can immerse the solid lithium supplement agent.

[0033] Specifically, after the heating in S3, the following steps are further included: filtering while hot to obtain the lithium-supplementing positive electrode black powder and excess lithium-supplementing agent. After the lithium-supplementing agent is regenerated, a certain amount of organic solvent can be replenished and recycled.

[0034] The present invention also provides application of the above regeneration method in recycling waste lithium-ion batteries.

[0035] The present invention also provides a lithium ion battery positive electrode material, which is prepared by adopting the above regeneration method.

[0036] The present invention also provides a lithium ion battery, which is assembled using the lithium ion battery positive electrode material.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The invention provides a method for regenerating positive electrode materials of waste lithium-ion batteries, which effectively realizes the recovery and regeneration of positive electrode materials of lithium-ion batteries through processes such as discharge, pyrolysis, lithium supplementation and regeneration.

[0039] In view of the insufficient transport power of lithium ions in the current lithium replenishment technology, the present invention configures a lithium replenisher comprising lithium salt, lithium hydroxide, trace additives and organic solvents, and cooperates with vacuum post-high pressure lithium replenishment technology to enable the lithium replenisher to be directionally transported to the defects, thereby achieving effective lithium replenishment.

[0040] Aiming at the instability of the structure of the positive electrode material of the lithium-ion battery, the present invention sets a specific calcination regeneration procedure. The material is first calcined at a low temperature. The presence of trace additives can introduce a chemical short-range disordered structure inside the positive electrode material of the lithium-ion battery, and the lithium supplement will also overflow to the surface during the calcination process to form a structure with disordered bulk doping and surface coating. Subsequently, the material is calcined at a high temperature to obtain an ordered structure of the main body.

[0041] The regenerated positive electrode material obtained by the present invention exhibits good electrochemical performance under high voltage. The first cycle capacity at 4.6V voltage and 1C is basically greater than 188mAh / g, and the capacity retention rate after 400 cycles is greater than 80%. It has high capacity and good high-rate cycle stability under high voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a SEM image of the positive electrode black powder obtained after being processed in steps S1 and S2 in Example 1.

[0043] Figure 2This is the SEM image of the regenerated positive electrode material prepared in Example 1.

[0044] Figure 3 This is a spherical aberration electron microscope image of the regenerated positive electrode material prepared in Example 1.

[0045] Figure 4 This is a comparison chart of the battery long cycle of the regenerated positive electrode material prepared in Example 1 and the commercial positive electrode material.

[0046] Figure 5 Flow chart of the preparation method of Example 1. DETAILED DESCRIPTION

[0047] The content of the present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present embodiment are conventional reagents, methods and equipment in the art.

[0048] Embodiment 1

[0049] A method for regenerating waste lithium-ion battery positive electrode materials comprises the following steps:

[0050] S1. Discharge: Cover the waste lithium-ion battery with a conductive medium and discharge it to a voltage of 2.5V, then immerse the waste lithium-ion battery with 2 mol / L lithium salt and discharge it completely to obtain a positive electrode sheet;

[0051] The positive electrode material of the waste lithium-ion battery is lithium cobalt oxide; the conductive medium is copper powder, and the lithium salt is lithium chloride;

[0052] S2, pyrolysis: pyrolyzing the positive electrode sheet at 450° C. in an oxygen atmosphere for 1 h, crushing and sieving with a 200-mesh sieve to obtain positive electrode black powder;

[0053] S3, lithium replenishment: the positive electrode black powder and the lithium replenishing agent are mixed, and vacuum is drawn, the vacuum pressure is 0.1 Pa, and the vacuum is maintained for 15 minutes; the vacuum is stopped, and then heated, the heating temperature is 150° C., and the heating is maintained for 30 minutes to obtain lithium replenishing positive electrode black powder;

[0054] The lithium supplement agent is a mixture of lithium salt, lithium hydroxide, trace additives and organic solvents, the trace additive is magnesium sulfate, the lithium salt is lithium iodide, the amount of the lithium salt and the lithium hydroxide is 0.5 mol respectively, the amount of the trace additive added is 2% of the total mass of the positive electrode black powder, and the organic solvent is ethanol;

[0055] S4, regeneration: the lithium-supplemented positive electrode black powder is heated to 650°C at a heating rate of 2°C / min in an air atmosphere, maintained for 12 hours, and then heated to 1000°C at a heating rate of 10°C / min in an oxygen atmosphere, maintained for 5 hours, to obtain a regenerated positive electrode material.

[0056] Embodiments 2 to 6

[0057] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0058] Embodiment 2: In S1, the conductive medium is copper powder, and the lithium salt is lithium sulfate;

[0059] Embodiment 3: In S1, the conductive medium is aluminum powder, and the lithium salt is lithium chloride;

[0060] Embodiment 4: In S1, the conductive medium is aluminum powder, and the lithium salt is lithium sulfate;

[0061] Embodiment 5: In S1, the conductive medium is graphite powder, and the lithium salt is lithium chloride;

[0062] Embodiment 6: In S1, the conductive medium is graphite powder, and the lithium salt is lithium sulfate.

[0063] Embodiments 7 to 10

[0064] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0065] Embodiment 7: In the S2, the pyrolysis temperature is 350°C;

[0066] Embodiment 8: In S2, the pyrolysis temperature is 400°C;

[0067] Embodiment 9: In S2, the pyrolysis temperature is 500°C;

[0068] Embodiment 10: In the S2, the pyrolysis temperature is 550°C.

[0069] Embodiment 11-12

[0070] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0071] Embodiment 11: In S2, 250 mesh screen is used for screening;

[0072] Embodiment 12: In S2, a 300-mesh sieve is used for screening.

[0073] Embodiment 13 to 16

[0074] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0075] Embodiment 13: In S3, the lithium salt is lithium sulfate;

[0076] Embodiment 14: In S3, the trace additive is aluminum oxide;

[0077] Embodiment 15: In S3, the trace additive is titanium trioxide;

[0078] Embodiment 16: In S3, the organic solvent is acetone.

[0079] Embodiment 17-18

[0080] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0081] Embodiment 17: The positive electrode material of the waste lithium-ion battery is lithium-rich lithium manganese oxide;

[0082] Embodiment 18: The positive electrode material of the waste lithium-ion battery is NCM811.

[0083] Embodiments 19 to 23

[0084] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0085] Embodiment 19: S1, discharge: covering the waste lithium-ion battery with a conductive medium, and completely discharging it to obtain a positive electrode sheet; the conductive medium is copper powder;

[0086] Embodiment 20: S1, discharge: Cover the waste lithium-ion battery with a conductive medium, discharge it completely, and obtain a positive electrode sheet; the conductive medium is aluminum powder;

[0087] Embodiment 21: S1, discharge: covering the waste lithium-ion battery with a conductive medium, and completely discharging the battery to obtain a positive electrode sheet; the conductive medium is graphite powder;

[0088] Example 22: S1, discharge: using 0.5 mol / L lithium salt to immerse the waste lithium-ion battery, and discharge it completely to obtain a positive electrode sheet; the lithium salt is lithium chloride;

[0089] Example 23: S1. Discharge: Use 0.2 mol / L lithium salt to immerse the waste lithium-ion battery, discharge it completely, and obtain a positive electrode sheet; the lithium salt is lithium sulfate.

[0090] Comparative Example 1

[0091] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0092] In the S2, the pyrolysis temperature is 250°C.

[0093] Comparative Example 2

[0094] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0095] In S3, the amount of the trace additive added is 5% of the total mass of the positive electrode black powder.

[0096] Comparative Examples 3-4

[0097] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0098] Comparative Example 3: In S4, the holding time after the first heating is 5 h;

[0099] Comparative Example 4: In S4, the holding time after the second temperature increase is 10 h.

[0100] Comparative Examples 5-6

[0101] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0102] Comparative Example 5: In S2, 50-mesh sieve was used for screening;

[0103] Comparative Example 6: In S2, 100-mesh sieve was used for screening.

[0104] Comparative Examples 7-9

[0105] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0106] Comparative Example 7: The lithium supplement agent in S3 does not contain an organic solvent;

[0107] Comparative Example 8: The lithium supplement described in S3 does not contain trace additives;

[0108] Comparative Example 9: S3, lithium supplementation: the positive electrode black powder and the lithium supplementation agent are mixed, and heated at a heating temperature of 150° C. for a heating holding time of 30 min to obtain a lithium supplementation positive electrode black powder.

[0109] Comparative Examples 10-11

[0110] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0111] Comparative Example 10: S4, regeneration: the lithium-supplemented positive electrode black powder is heated to 650° C. at a heating rate of 2° C. / min in an air atmosphere, and maintained for 12 hours to obtain a regenerated positive electrode material;

[0112] Comparative Example 11: S4, regeneration: the lithium-supplemented positive electrode black powder is heated to 1000° C. at a heating rate of 10° C. / min in an oxygen atmosphere and maintained for 5 hours to obtain a regenerated positive electrode material.

[0113] Comparative Example 12

[0114] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0115] In the S2, the pyrolysis temperature is 300°C.

[0116] Comparative Example 13

[0117] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0118] In the S2, a 150-mesh sieve is used for screening.

[0119] Comparative Example 14~15

[0120] A method for regenerating anode materials of waste lithium-ion batteries, which differs from the first embodiment only in that:

[0121] Comparative Example 14: In S4, the heating rate of the first heating is 10°C / min;

[0122] Comparative Example 15: In S4, the heating rate of the second heating is 2°C / min.

[0123] Performance Testing

[0124] 1. Discharge efficiency of different discharge methods

[0125] Table 1 Discharge efficiency of different discharge methods

[0126]

[0127] As can be seen from Table 1, the physical and chemical combined discharge method can reduce the maximum temperature of the battery during discharge on the one hand, and increase the discharge rate on the other hand.

[0128] 2. Specific surface area of ​​positive electrode black powder at different pyrolysis temperatures

[0129] Table 2 Specific surface area of ​​positive electrode materials after pyrolysis at different pyrolysis temperatures

[0130]

[0131] Among them, the stripping rate = positive electrode material mass / positive electrode sheet mass × 0.85.

[0132] It can be seen from Table 2 that the pyrolysis temperature has a significant effect on the specific surface area and stripping rate of the positive electrode material after pyrolysis, which further affects the electrochemical performance of the regenerated positive electrode material.

[0133] 3. The percentage of metallic aluminum in the positive electrode material under different sieve meshes

[0134] Table 3 The percentage of aluminum in the positive electrode material at different mesh sizes

[0135]

[0136] It can be seen from Table 3 that, taking metal aluminum as an example, different sieving mesh sizes have a significant impact on the impurity content in the sieved materials, which further affects the electrochemical properties of the regenerated positive electrode materials.

[0137] 4. Structure and performance characterization of recycled cathode materials

[0138] 1. Structural characterization: Scanning electron microscopy and spherical aberration electron microscopy were used to analyze the surface characteristics of the regenerated positive electrode material prepared in Example 1. Figure 1 It can be seen that the positive electrode black powder obtained after discharge and pyrolysis has a rough and porous surface, which is conducive to lithium replenishment. Figure 2 It can be seen that the regenerated positive electrode material obtained after discharge, pyrolysis, lithium supplementation and regeneration has a smooth and flat surface, indicating that the structure is well repaired; Figure 3 It can be seen that atoms of trace elements appeared at the lithium site in the dark area. At the same time, a coating layer was formed on the outer layer of the regenerated positive electrode material. It can be seen that the regenerated positive electrode material has the characteristics of chemical short-range disorder and surface coating.

[0139] 2. Performance characterization: The regenerated positive electrode materials prepared in each embodiment and comparative example were assembled into a half-cell and tested. The regenerated positive electrode material, polyvinylidene fluoride (4% PVDF / NMP) and acetylene black in the half-cell positive electrode sheet were configured in a mass ratio of 8:1:1 and coated on the surface of the current collector. Metal lithium was used as the negative electrode sheet and lithium hexafluorophosphate electrolyte (1M LiPF6 dissolved in a solvent of EC:DEC=1:1) was used as the electrolyte. After assembly, charge and discharge tests were carried out at a voltage range of 3.0-4.6 V and a current density of 1C.

[0140] Depend on Figure 4It can be seen that compared with the commercial lithium cobalt oxide positive electrode material, the regenerated positive electrode material prepared in Example 1 has a capacity of up to 200 mAh / g at a voltage of 4.6 V and a current of 1 C, and a capacity retention rate of 87.56% after 400 cycles, which is better than the commercial lithium cobalt oxide positive electrode material. This shows that the method of the present invention can effectively recycle and regenerate high-voltage positive electrode materials and greatly improve the chemical stability of the regenerated positive electrode materials.

[0141] Table 4 shows the half-cell performance test results of the regenerated positive electrode materials obtained in each embodiment and comparative example. It can be seen from Table 4 that each embodiment has good electrochemical performance, among which the regenerated positive electrode material prepared from waste lithium cobalt oxide has a first cycle capacity of basically >188mAh / g at 4.6V voltage and 1C, and the capacity retention rate after 400 cycles is greater than 80%; the regenerated positive electrode material prepared from waste lithium-rich lithium manganese oxide or waste NCM811 has a first cycle capacity at 4.6V and 1C and a capacity retention rate after 400 cycles that are better than commercial lithium-rich lithium manganese oxide or commercial NCM811.

[0142] In Comparative Examples 1 and 12, the pyrolysis temperature is low, and the overall performance of the obtained regenerated positive electrode materials is reduced. In Comparative Example 2, too much trace additive is added, resulting in too much disordered structure in the obtained regenerated positive electrode material and low capacity; in Comparative Examples 3 to 4, the holding time after the first heating is too short or the holding time after the second heating is too long, and in Comparative Examples 14 to 15, the first heating rate is too fast or the second heating rate is too slow, and the disordered structure in the obtained regenerated positive electrode material is insufficient, resulting in a lower capacity retention rate; in Comparative Examples 5 to 6 and Comparative Example 13, the sieving mesh size is too small, and there are too many impurities in the material after sieving, and the first cycle capacity and capacity retention rate are significantly reduced; in Comparative Example 7, no organic solvent is added to the lithium supplement, and the lithium supplement In the comparative example 8, no trace additive is added to the lithium replenishing agent, and a disordered structure cannot be formed in the obtained regenerated positive electrode material, resulting in a significant decrease in the capacity retention rate; in the comparative example 9, no vacuum is drawn before lithium replenishment, and the gas in the gap of the positive electrode material cannot be effectively extracted, resulting in a decrease in the lithium replenishing effect, thereby resulting in a decrease in the overall performance of the obtained positive electrode material; in the comparative examples 10 to 11, only low-temperature calcination or only high-temperature calcination is performed, and the chemical short-range disordered and main ordered material structure of the present invention cannot be obtained, and the performance is greatly reduced.

[0143] Table 4 Half-cell performance test of the regenerated positive electrode materials obtained in each embodiment and comparative example

[0144]

[0145]

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for regenerating anode materials of waste lithium-ion batteries, comprising the following steps: S1. Discharge: Discharge the waste lithium-ion battery completely and disassemble it to obtain the positive electrode sheet; S2, pyrolysis: pyrolyze the positive electrode sheet in an oxygen-containing atmosphere, the pyrolysis temperature is ≥350°C, the pyrolysis time is 0.5-3h, crush and sieve to obtain positive electrode black powder; the sieving adopts a 200-300 mesh sieve; S3, lithium replenishment: the positive electrode black powder and the lithium replenishing agent are mixed, vacuumed, the ultimate pressure is 0.1-2Pa, and the vacuum is maintained for 5-30min; the vacuum is stopped, and then heated, the heating temperature is 60-150°C, and the heating is maintained for 20-60min to obtain the lithium replenishing positive electrode black powder; The lithium supplement agent is a mixture of lithium salt, lithium hydroxide, trace additives and organic solvents, the trace additives are selected from at least one of aluminum compounds, magnesium compounds or titanium compounds, the molar ratio of the lithium salt to the lithium hydroxide is (1-3):1, the amount of the trace additive added does not exceed 2-4% of the total mass of the positive electrode black powder, and the boiling point of the organic solvent is lower than 150°C; S4, regeneration: the lithium-supplemented positive electrode black powder is heated to 200-600°C for the first time in an air atmosphere at a heating rate of 2-5°C / min, and maintained for 10-20 hours, and then heated to 800-1100°C for a second time in an oxygen atmosphere at a heating rate of 10-40°C / min, and maintained for 2-6 hours to obtain a regenerated positive electrode material.

2. The regeneration method according to claim 1, characterized in that: The S1 comprises the following steps: covering the waste lithium-ion battery with a conductive medium, discharging it to a voltage of 2.0-3.0V, then immersing the waste lithium-ion battery with 1-3 mol / L lithium salt, completely discharging it, and disassembling it to obtain a positive electrode sheet.

3. The regeneration method according to claim 2, characterized in that: The conductive medium is selected from at least one of copper powder, aluminum powder or graphite powder; and the lithium salt is selected from at least one of lithium chloride or lithium sulfate.

4. The regeneration method according to claim 1, characterized in that: The oxygen-containing atmosphere in S2 is selected from at least one of an air atmosphere and an oxygen atmosphere.

5. The regeneration method according to claim 1, characterized in that: The lithium salt in S3 is selected from at least one of lithium fluoride, lithium chloride, lithium iodide or lithium sulfate.

6. The regeneration method according to claim 1, characterized in that: The aluminum compound in S3 is selected from at least one of aluminum chloride, aluminum oxide or aluminum hydroxide; the magnesium compound is selected from at least one of magnesium chloride, magnesium oxide or magnesium sulfate; and the titanium compound is selected from at least one of titanium oxide and titanium trioxide.

7. The regeneration method according to claim 1, characterized in that: The organic solvent in S3 is selected from at least one of methanol, ethanol, propanol, butanol, pentanol or acetone.

8. Use of the regeneration method according to any one of claims 1 to 7 in recycling waste lithium-ion batteries.

9. A positive electrode material for a lithium-ion battery, prepared by the regeneration method according to any one of claims 1 to 7.

10. A lithium ion battery assembled using the lithium ion battery positive electrode material according to claim 9.

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