Waste positive electrode material full-chain integrated repair and regeneration method and application thereof

Abstract

Provided in the present application are a waste positive electrode material full-chain integrated repair and regeneration method and an application thereof. The method comprises the following steps: (1) mixing waste positive electrode material with a sodium source, and performing calcination treatment to obtain sodium-doped waste positive electrode material; (2) taking the sodium-doped waste positive electrode material as an adsorbent for performing carbon dioxide adsorption treatment to obtain adsorbed positive electrode material; and (3) mixing the adsorbed positive electrode material with a carbon-containing lithium source, and performing sintering treatment to obtain repaired and regenerated positive electrode material. The doped sodium ions in the repair and recovery process increase the carbon dioxide adsorption efficiency and also replace lithium, so that the structural stability of the positive electrode material can be effectively improved while lithium defects are repaired, reducing the capacity loss of the electrode material during charging and discharging; the valence of nickel ions can also be stabilised, lithium-nickel mixing can be reduced, and to a certain extent phase changes during charging and discharging can be inhibited, thereby improving structural stability and electrochemical performance.

Description

A full-chain integrated repair and regeneration method for waste cathode materials and its application Technical Field

[0001] The embodiments of the present application relate to the field of resource recycling technology, for example, a full-chain integrated repair and regeneration method for waste positive electrode materials and its application. Background Art

[0002] Lithium-ion batteries are widely used in electronic devices and electric vehicles due to their high energy density, long cycle life, and lightweight properties. Ternary lithium-ion batteries, a key type of lithium-ion battery, boast high energy density and excellent cycle performance, and currently occupy a dominant position in applications such as electric vehicles. The valuable metal ions in the cathode materials of ternary lithium-ion batteries are diverse and high in content. Therefore, efficient, environmentally friendly, and cost-effective recycling of spent ternary lithium-ion batteries is of great importance. Currently, recycling technologies for ternary cathode materials (NCMs) in lithium-ion batteries primarily include pyrometallurgical and hydrometallurgical direct recovery methods. While pyrometallurgical and hydrometallurgical methods can return valuable metals such as lithium, cobalt, and nickel to the lithium-ion battery production chain, the complete destruction of the cathode particles reduces the high added value of the composite structure. The key to direct recycling technology is to repair the composition and structural defects of degraded lithium-deficient cathode particles in retired lithium-ion batteries, thereby maximizing the preservation of the high added value of the cathode particles.

[0003] Current direct repair technologies primarily include hydrothermal, molten salt, and solid-state sintering. The hydrothermal method uses water as a solvent and lithium hydroxide as a carbonaceous lithium source to recharge spent lithium-ion battery ternary cathode materials under high temperature and pressure. After recharge, excess lithium salts are removed by washing and sintering is performed at high temperature. The capacity retention of hydrothermally reconditioned ternary cathode materials after 100 cycles at 1C is 82%, lower than that of commercial ternary cathode materials. Furthermore, the hydrothermal method requires reaction temperatures typically above 220°C, resulting in high pressures and potential hazards. Similar to solid-state sintering, the molten salt method combines spent lithium-ion battery ternary cathode materials with lithium salts and heats them, utilizing the free diffusion of lithium ions at high temperatures to repair lithium defects. However, the slow diffusion kinetics of lithium ions prevent the effective repair of lithium defects in the spent lithium-ion battery cathode materials. This results in lower electrochemical capacity for the reconditioned ternary cathode materials. Furthermore, the ternary materials also suffer from issues such as gassing, structural and interfacial phase transitions, and poor thermal stability due to lattice oxygen release.

[0004] CN114204013A discloses a method for directly repairing waste ternary lithium battery positive electrode materials, comprising the following steps: after low-temperature pretreatment, the active material is placed in distilled water for ultrasonication and separated from the aluminum foil current collector to obtain a positive electrode powder material; the obtained positive electrode powder material is uniformly mixed with a certain amount of ternary molten salt and a co-solvent, and lithium replenishment and impurity removal operations are performed simultaneously at a low temperature; the washed and dried lithium replenishment powder is heat-treated under oxygen and high temperature conditions to obtain a repaired positive electrode material.

[0005] CN112909370A discloses a method for repairing ternary positive electrode materials in waste lithium batteries. The method heat-treats the disassembled waste positive electrode sheets, cools them in the furnace to obtain waste positive electrode materials, washes the waste positive electrode materials with alkaline solution and then dries them. The waste positive electrode materials are then loaded into a crucible and placed in a resistance furnace for heating treatment. After being taken out, they are ground and pressed into sheets, and then placed in the resistance furnace for heating treatment. After cooling, they are taken out again and ground and crushed to obtain the repaired positive electrode materials.

[0006] After repair by the above scheme, the electrochemical capacity of the ternary positive electrode material is low, and the ternary material is prone to problems such as battery gas production, structural and interface phase changes, and poor thermal stability due to lattice oxygen release.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The embodiments of the present application provide a full-chain integrated repair and regeneration method for waste positive electrode materials and its application. The sodium ions doped in the recycling and repair process of the present application can not only increase the carbon dioxide adsorption efficiency, but also replace lithium. While repairing lithium defects, it can also effectively improve the structural stability of the positive electrode material, reduce the capacity loss of the electrode material during the charging and discharging process, stabilize the valence of nickel ions, reduce lithium-nickel mixing, and to a certain extent inhibit the phase change during the charging and discharging process, thereby improving the structural stability and electrochemical performance.

[0010] In a first aspect, the present invention provides a method for repairing and regenerating waste cathode materials in an integrated manner, the method comprising the following steps:

[0011] (1) mixing the waste positive electrode material with a sodium source and calcining the mixture to obtain a sodium-doped waste positive electrode material;

[0012] (2) using the sodium-doped waste positive electrode material as an adsorbent to adsorb carbon dioxide to obtain an adsorbed positive electrode material;

[0013] (3) The adsorbed positive electrode material is mixed with a carbon-containing lithium source, and sintered to obtain a repaired and regenerated positive electrode material.

[0014] The present application heat-treats waste ternary materials while doping them with sodium ions, which can effectively activate the ternary materials. In addition, since the radius of the doped sodium ions is slightly larger than that of the lithium ions, the doping of sodium can form defects in the structure, which is beneficial to further improve the activity of the material, increase the rate at which the material adsorbs carbon dioxide, and increase the resource utilization rate of carbon dioxide. The waste ternary materials that have adsorbed carbon dioxide and doped with sodium are then calcined at high temperature with carbon-containing lithium salts to replenish lithium and repair the waste ternary materials. The carbon dioxide released during the heat treatment process can modify the surface of the ternary positive electrode material and form oxygen vacancies in the area near the surface of the material. Before charging, part of the lattice oxygen of the ternary material can be extracted by CO2. The pre-activated surface layer of the modified sample with oxygen vacancies reduces the oxygen partial pressure on the surface, which can suppress the release of gaseous oxygen during platform charging.

[0015] Preferably, the sodium source in step (1) comprises any one of sodium carbonate, sodium oxalate or sodium nitrate, or a combination of at least two of them.

[0016] Preferably, the molar ratio of the total molar amount of transition metals in the waste positive electrode material to the sodium element in the sodium source is 10:(0.5-1), for example: 10:0.5, 10:0.6, 10:0.8, 10:0.9 or 10:1, etc.

[0017] Preferably, the mixing method in step (1) includes ball milling.

[0018] Preferably, the ball milling time is 4 to 6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0019] Preferably, the temperature of the calcination treatment in step (1) is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C.

[0020] Preferably, the calcination treatment time is 4 to 8 hours, for example: 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0021] Preferably, the temperature of the carbon dioxide adsorption treatment in step (2) is 500-700°C, for example, 500°C, 550°C, 600°C, 650°C or 700°C.

[0022] Preferably, the carbon dioxide adsorption treatment time is 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0023] Preferably, the waste gas flow rate for the carbon dioxide adsorption treatment is 5.5 to 15.5 L / min, for example, 5.5 L / min, 6 L / min, 8 L / min, 10 L / min or 15.5 L / min.

[0024] Preferably, the carbon-containing lithium source in step (3) includes lithium carbonate and / or lithium oxalate.

[0025] Preferably, the molar ratio of the total molar amount of transition metal in the adsorbed positive electrode material to the lithium element in the carbon-containing lithium source is 1:(1-1.06), for example: 1:1, 1:1.01, 1:1.02, 1:1.04 or 1:1.06, etc.

[0026] Preferably, the mixing method in step (3) includes ball milling.

[0027] Preferably, the ball milling time is 4 to 6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours.

[0028] Preferably, the atmosphere of the sintering treatment in step (3) includes ammonia.

[0029] This application uses ammonia as the atmosphere for sintering treatment. Ammonia can provide H + , maintaining charge balance. At the same time, due to the formation of oxygen vacancies, the lithium in the tetrahedral position is activated and the release of surface oxygen is suppressed, which can increase the lithium ion diffusion layer, stabilize the transition metal layer, and reduce the side reactions of the material with the electrolyte and oxygen, so that the modified ternary material has higher discharge capacity and better rate performance.

[0030] Preferably, the sintering temperature is 700-900°C, for example, 700°C, 750°C, 800°C, 850°C or 900°C.

[0031] Preferably, the sintering treatment time is 8 to 15 hours, for example, 8 hours, 9 hours, 10 hours, 12 hours or 15 hours.

[0032] Preferably, during the sintering process, the filling amount of the adsorbed positive electrode material is 5% to 15%, for example, 5%, 8%, 10%, 12% or 15%.

[0033] As a preferred embodiment of the present application, the repair and regeneration method comprises the following steps:

[0034] (1) mixing the waste cathode material with a sodium source according to M / Na=10:(0.5-1) and ball milling for 4-6 hours, and calcining at 600-800°C for 4-8 hours to obtain a sodium-doped waste cathode material;

[0035] (2) placing the sodium-doped waste cathode material as an adsorbent in a carbon dioxide absorption tower, at 500-700° C., allowing carbon dioxide to enter the absorption tower and directly contact the adsorbent to capture carbon dioxide, and removing the adsorbent after adsorption for 2-6 hours to obtain an adsorbed cathode material;

[0036] (3) The adsorbed positive electrode material and the carbon-containing lithium source are mixed and ball-milled at M / Li=1:(1-1.06) for 4-6 hours, and sintered at 700-900°C for 8-15 hours under an ammonia atmosphere to obtain a repaired and regenerated positive electrode material.

[0037] In a second aspect, an embodiment of the present application provides an application of the repair and regeneration method as described in the first aspect, wherein the repair and regeneration method is used for repair and regeneration of lithium-ion battery positive electrode materials and carbon dioxide adsorption.

[0038] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0039] (1) The sodium ions doped in the recovery and repair process of the embodiment of the present application can not only increase the carbon dioxide adsorption efficiency, but also replace lithium. While repairing lithium defects, it can also effectively improve the structural stability of the positive electrode material, reduce the capacity loss of the electrode material during the charge and discharge process, stabilize the valence of nickel ions, reduce lithium and nickel mixing, and to a certain extent inhibit the phase change during the charge and discharge process, thereby improving the structural stability and electrochemical performance.

[0040] (2) The battery made of the positive electrode material repaired and regenerated by the method described in the embodiment of the present application can have an initial charging capacity of more than 201.6 mAh / g, an initial discharge capacity of more than 175.2 mAh / g, an initial efficiency of more than 86.9%, and a capacity retention rate of more than 92.1% after 100 cycles of charge and discharge at 1C.

[0041] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0042] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0043] The waste ternary positive electrode materials used in the examples and comparative examples of the present application are all NCM811 positive electrode materials.

[0044] Example 1

[0045] This embodiment provides a method for repairing and regenerating waste cathode materials in an integrated manner, the method comprising the following steps:

[0046] (1) The ternary material and sodium carbonate were placed in a double planetary ball mill at a ratio of M / Na = 10:0.7 and ball-milled at 200 rpm for 5 h. The ball-milling dispersant was anhydrous ethanol with a volume twice that of the powder. The mixture was calcined at 700 °C for 6 h to obtain sodium-doped waste cathode material.

[0047] (2) The sodium-doped waste cathode material is placed as an adsorbent in a carbon dioxide absorption tower. At 600° C., carbon dioxide enters the absorption tower and directly contacts the adsorbent to capture carbon dioxide. The exhaust gas flow rate is 10.5 L / min. After adsorption for 4 hours, the adsorbent is removed to obtain an adsorbed cathode material.

[0048] (3) The adsorbed positive electrode material and lithium carbonate were mixed and ball-milled at a ratio of M / Li = 1:1.03 for 5 h, and the ball-milled material was filled into a sealed container at a volume ratio of 10%, and sintered at 800 ° C for 11 h under an ammonia atmosphere to obtain a repaired and regenerated positive electrode material.

[0049] Example 2

[0050] This embodiment provides a method for repairing and regenerating waste cathode materials in an integrated manner, the method comprising the following steps:

[0051] (1) The ternary material and sodium oxalate were placed in a double planetary ball mill at a ratio of M / Na = 10:1 and ball-milled at 200 rpm for 5 h. The ball-milling dispersant was anhydrous ethanol with a volume twice that of the powder. The material was calcined at 600 °C for 8 h to obtain sodium-doped waste cathode material.

[0052] (2) The sodium-doped waste cathode material is placed as an adsorbent in a carbon dioxide absorption tower. At 500° C., carbon dioxide enters the absorption tower and directly contacts the adsorbent to capture carbon dioxide. The exhaust gas flow rate is 5.5 L / min. The adsorption is carried out for 6 hours and the adsorbent is removed to obtain an adsorbed cathode material.

[0053] (3) The adsorbed positive electrode material and lithium oxalate were mixed and ball-milled at a ratio of M / Li = 1:1 for 5 h, and the ball-milled material was filled into a sealed container at a volume ratio of 5%, and sintered at 700 ° C for 15 h under an ammonia atmosphere to obtain a repaired and regenerated positive electrode material.

[0054] Example 3

[0055] This embodiment provides a method for repairing and regenerating waste cathode materials in an integrated manner, the method comprising the following steps:

[0056] (1) The ternary material and sodium nitrate were placed in a double planetary ball mill at a ratio of M / Na = 10:0.5 and ball-milled at 200 rpm for 5 h. The ball-milling dispersant was anhydrous ethanol with a volume twice that of the powder. The material was calcined at 800 °C for 4 h to obtain sodium-doped waste cathode material.

[0057] (2) The sodium-doped waste cathode material is placed as an adsorbent in a carbon dioxide absorption tower. At 700° C., carbon dioxide enters the absorption tower and directly contacts the adsorbent to capture carbon dioxide. The exhaust gas flow rate is 15.5 L / min. After adsorption for 2 hours, the adsorbent is removed to obtain an adsorbed cathode material.

[0058] (3) The adsorbed positive electrode material and lithium oxalate were mixed and ball-milled at a ratio of M / Li = 1:1.06 for 5 h, and the ball-milled material was filled into a sealed container at a volume ratio of 15%, and sintered at 900 °C for 8 h under an ammonia atmosphere to obtain a repaired and regenerated positive electrode material.

[0059] Example 4

[0060] The only difference between this embodiment and embodiment 1 is that M / Na=10:0.3, and other conditions and parameters are exactly the same as those in embodiment 1.

[0061] Example 5

[0062] The only difference between this embodiment and embodiment 1 is that M / Na=10:1.2, and other conditions and parameters are exactly the same as those in embodiment 1.

[0063] Comparative Example 1

[0064] The only difference between this comparative example and Example 1 is that no sodium source is added in step (1), and the other conditions and parameters are exactly the same as those in Example 1.

[0065] Comparative Example 2

[0066] The only difference between this comparative example and Example 1 is that step (2) does not adsorb carbon dioxide, and the other conditions and parameters are exactly the same as those in Example 1.

[0067] Comparative Example 3

[0068] The only difference between this comparative example and Example 1 is that lithium carbonate is replaced with lithium hydroxide in step (3), and the other conditions and parameters are exactly the same as those in Example 1.

[0069] Comparative Example 4

[0070] The only difference between this comparative example and Example 1 is that ammonia is not used as the sintering atmosphere in step (3), and the other conditions and parameters are exactly the same as those in Example 1.

[0071] Performance testing:

[0072] The positive electrode material obtained in Example 1 and the comparative example was mixed with the conductive active material SuperP and the binder PVDF in a ratio of 90:5:5 to form a slurry, which was then evenly coated on aluminum foil to prepare a positive electrode sheet. A high-purity lithium sheet was selected as the negative electrode, and the separator was a Celgard 2400 polypropylene separator. The electrolyte was 1 mol / L LiPF6 dissolved in a mixed solvent of EC and DMC (volume ratio of 1:1). CR2032 button cells were assembled in a vacuum glove box and then electrochemically tested. Charge and discharge tests were performed using a LAND-2001 blue electric test system with a charge and discharge range of 3.0-4.3V and a temperature of 25°C. The test results are shown in Table 1:

[0073] Table 1

[0074] As can be seen from Table 1, from Examples 1-3, the battery made of the positive electrode material repaired and regenerated by the method described in this application can have an initial charging capacity of more than 201.6 mAh / g, an initial discharge capacity of more than 175.2 mAh / g, an initial efficiency of more than 86.9%, and a capacity retention rate of more than 92.1% after 100 cycles of charge and discharge at 1C.

[0075] By comparing Example 1 with Examples 4-5, it can be seen that in the repair and regeneration method described in the present application, the amount of sodium source added will affect the repair effect. The molar ratio of the total molar amount of transition metals in the waste positive electrode material to the molar ratio of the sodium element in the sodium source is controlled at 10: (0.5~1), and the repair and regeneration effect is better. If the amount of sodium source added is too low, the content of sodium ions doped in the positive electrode material is too small, and it cannot play a role in stabilizing the material structure. If the amount of sodium source added is too high, too many sodium ions will occupy the lithium site, thereby affecting the diffusion of lithium ions and reducing the cycle performance of the material.

[0076] By comparing Example 1 and Comparative Example 1, it can be seen that the present application can effectively activate the ternary material by doping sodium ions while subjecting the waste ternary material to heat treatment. In addition, since the radius of the doped sodium ions is slightly larger than that of the lithium ions, the doping of sodium can form defects in the structure, which is beneficial to further improve the activity of the material, increase the rate at which the material adsorbs carbon dioxide, and increase the resource utilization rate of carbon dioxide.

[0077] From the comparison between Example 1 and Comparative Example 2, it can be seen that the present application uses sodium-doped waste positive electrode materials to adsorb sodium, and the modification of surface carbon dioxide inhibits the irreversible oxygen release in the first cycle, and the voltage decay problem during the cycle is greatly improved.

[0078] Comparison of Example 1 and Comparative Example 3 demonstrates that this application involves high-temperature calcination of waste cathode materials that have adsorbed carbon dioxide and doped with sodium with carbon-containing lithium salts to repair the waste ternary materials with lithium. The carbon dioxide released during the heat treatment can modify the surface of the ternary cathode material, forming oxygen vacancies near the surface of the material. Before charging, some of the lattice oxygen in the ternary material can be extracted by CO2. The pre-activated surface layer of the modified sample with oxygen vacancies reduces the oxygen partial pressure on the surface, suppressing the release of gaseous oxygen during platform charging.

[0079] From the comparison between Example 1 and Comparative Example 4, it can be seen that the present invention is sintered in an ammonia atmosphere, which can provide H + , maintaining charge balance. At the same time, due to the formation of oxygen vacancies, the lithium in the tetrahedral position is activated and the release of surface oxygen is suppressed, which can increase the lithium ion diffusion layer, stabilize the transition metal layer, and reduce the side reactions of the material with the electrolyte and oxygen, so that the modified ternary material has higher discharge capacity and better rate performance.

[0080] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A full-chain integrated repair and regeneration method for waste positive electrode materials, comprising the following steps: (1) mixing the waste positive electrode material with a sodium source and calcining the mixture to obtain a sodium-doped waste positive electrode material; (2) using the sodium-doped waste positive electrode material as an adsorbent to adsorb carbon dioxide to obtain an adsorbed positive electrode material; (3) The adsorbed positive electrode material is mixed with a carbon-containing lithium source, and sintered to obtain a repaired and regenerated positive electrode material.

2. The repair and regeneration method according to claim 1, wherein: The sodium source in step (1) includes any one of sodium carbonate, sodium oxalate or sodium nitrate, or a combination of at least two of them.

3. The repair and regeneration method according to claim 1 or 2, wherein: The molar ratio of the total molar amount of transition metals in the waste positive electrode material to the sodium element in the sodium source is 10: (0.5-1).

4. The repair and regeneration method according to any one of claims 1 to 3, wherein: The mixing method in step (1) includes ball milling.

5. The repair and regeneration method according to any one of claims 1 to 4, wherein: The ball milling time is 4 to 6 hours.

6. The repair and regeneration method according to any one of claims 1 to 5, wherein: The temperature of the calcination treatment in step (1) is 600-800°C.

7. The repair and regeneration method according to any one of claims 1 to 6, wherein: The calcination time is 4 to 8 hours.

8. The repair and regeneration method according to any one of claims 1 to 7, wherein: The temperature of the carbon dioxide adsorption treatment in step (2) is 500-700° C. Preferably, the carbon dioxide adsorption treatment time is 2 to 6 hours; Preferably, the waste gas flow rate of the carbon dioxide adsorption treatment is 5.5 to 15.5 L / min.

9. The repair and regeneration method according to any one of claims 1 to 8, wherein: The carbon-containing lithium source in step (3) includes lithium carbonate and / or lithium oxalate.

10. The repair and regeneration method according to any one of claims 1 to 9, wherein: The molar ratio of the total molar amount of transition metals in the adsorbed positive electrode material to the lithium element in the carbon-containing lithium source is 1:(1-1.06).

11. The repair and regeneration method according to any one of claims 1 to 10, wherein: The mixing method in step (3) includes ball milling; Preferably, the ball milling time is 4 to 6 hours.

12. The repair and regeneration method according to any one of claims 1 to 11, wherein: The atmosphere for the sintering treatment in step (3) includes ammonia.

13. The repair and regeneration method according to any one of claims 1 to 12, wherein: The sintering temperature is 700-900°C; Preferably, the sintering treatment time is 8 to 15 hours; Preferably, during the sintering process, the filling amount of the adsorbed positive electrode material is 5-15%.

14. The repair and regeneration method according to any one of claims 1 to 13, comprising the following steps: (1) mixing the waste positive electrode material with a sodium source according to M / Na=10:(0.5-1), ball milling for 4-6 hours, and calcining at 600-800°C for 4-8 hours to obtain a sodium-doped waste positive electrode material; (2) placing the sodium-doped waste positive electrode material as an adsorbent in a carbon dioxide absorption tower, wherein the carbon dioxide enters the absorption tower and directly contacts the adsorbent at 500-700° C. to capture the carbon dioxide, and after adsorption for 2-6 hours, the adsorbent is taken out to obtain an adsorbed positive electrode material; (3) The adsorbed positive electrode material and the carbon-containing lithium source are mixed and ball-milled for 4 to 6 hours according to M / Li=1:(1 to 1.06), and sintered at 700 to 900° C. for 8 to 15 hours under an ammonia atmosphere to obtain a repaired and regenerated positive electrode material.

15. An application of the repair and regeneration method according to any one of claims 1 to 14, wherein: The repair and regeneration method is used for repair and regeneration of lithium ion battery positive electrode materials and carbon dioxide adsorption.

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