Integrated regeneration method of waste lithium ion battery positive electrode material and application thereof

Abstract

An integrated regeneration method for waste lithium-ion battery cathode materials and its application belong to the field of waste battery recycling technology. The method includes: mixing waste cathode sheets with inorganic fillers, adding a dispersion medium, and ultrasonically treating the mixture to induce a dehydrofluorination reaction of PVDF at Lewis alkaline sites on the surface of the inorganic fillers, achieving efficient separation of the cathode material from the aluminum foil; cleaning the CEI layer on the cathode surface using in-situ generated HF; and washing, drying, and lithium-added sintering of the separated cathode powder, with the residual inorganic fillers and their derived phases forming a protective coating layer in one step. This invention integrates the separation, cleaning, and coating steps into a single process, avoiding the use of toxic organic solvents, significantly shortening the process flow, reducing costs and environmental impact, and producing regenerated cathode materials with excellent cycle stability, demonstrating significant economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery recycling technology, specifically relating to an integrated regeneration method for the cathode material of waste lithium-ion batteries, as well as the regenerated cathode material obtained by the method and a lithium battery containing the regenerated cathode material. Background Technology

[0002] In recent years, the global electric vehicle and new energy storage markets have experienced explosive growth, driving a rapid increase in demand for lithium-ion batteries and consequently increasing the demand for strategic resources such as lithium, nickel, cobalt, and manganese. At the same time, a large number of lithium-ion batteries face significant sustainable development challenges regarding their retirement and subsequent harmless disposal and resource utilization. The content of valuable metals in lithium-ion batteries is relatively well-defined, far exceeding that of natural ores; therefore, research on the resource recycling of spent lithium batteries is a necessary and urgent task.

[0003] Currently, the mainstream methods for recycling cathode materials from spent lithium-ion batteries mainly include pyrometallurgy and hydrometallurgy. Pyrometallurgy has the advantages of a wide range of raw materials that can be processed, large processing capacity, and simple process. However, this process usually requires high smelting temperatures (above 1400℃), resulting in high energy costs. It cannot directly recover lithium and also emits a large amount of harmful gases during the smelting process. Hydrometallurgy has the advantages of high metal recovery rate and product purity, low energy consumption, and no waste gas emissions. However, its process usually requires the use of corrosive solvents such as hydrochloric acid and sulfuric acid, resulting in disadvantages such as high reagent consumption and the need to treat large amounts of saline wastewater.

[0004] In spent lithium-ion battery cathode sheets, the cathode material and aluminum foil are firmly bonded together by polyvinylidene fluoride (PVDF) binder. Traditional recycling methods typically require the use of organic solvents such as N-methylpyrrolidone (NMP) at high temperatures to dissolve the PVDF and separate the cathode material from the aluminum foil. NMP is expensive, somewhat toxic, and requires a solvent recovery system, increasing recycling costs and environmental burden. Furthermore, the surface of the spent cathode material contains a thick and uneven solid electrolyte interface (CEI) layer, containing a large amount of decomposition products such as organic carbonates and organic lithium salts. These residues hinder lithium-ion transport and affect the electrochemical performance of the recycled material. Existing methods typically use alkaline washing or low-temperature calcination to remove the CEI layer, but alkaline washing generates large amounts of wastewater, and calcination is energy-intensive. To improve the cycle stability of the recycled cathode material, a coating layer is usually constructed on the material surface, but existing methods require the addition of a coating agent and secondary sintering, increasing process steps and costs.

[0005] Chinese patent CN110541077A discloses a method for recovering valuable components from waste lithium cobalt oxide battery cathode sheets. This method utilizes thermal desorption to remove residual electrolyte and organic binders from the cathode sheet, followed by hydraulic stirring to separate the cathode material from the aluminum foil, then separation using a sieving method, and finally purification of cobalt through acid leaching. However, this method still involves an acid leaching step, which presents problems related to reagent consumption and wastewater treatment.

[0006] A prior art patent with Chinese patent number CN 118639024 A discloses a method for recycling the cathode of a waste lithium-ion battery. This method combines the recycling of lithium cobalt oxide cathode with an aluminothermic reduction reaction, using aluminum foil in the cathode sheet as a reducing agent to reduce lithium cobalt oxide at high temperature to obtain metallic cobalt and metallic lithium. Although this method achieves the recycling of valuable metals, it still has the following shortcomings: (1) The aluminothermic reaction temperature is high (up to 3000℃ or more), which requires stringent equipment and poses safety hazards; (2) The reaction process is violent, and the reaction rate needs to be slowed down by amorphous carbon formed by PVDF carbonization, which requires high process control; (3) The product is metallic lithium and cobalt-aluminum alloy, which still needs to be further processed before it can be used to prepare new cathode materials, which is a long process; (4) This method is mainly for lithium cobalt oxide battery systems, and its applicability to ternary cathode materials has not been fully verified.

[0007] Therefore, there is an urgent need for a low-cost, environmentally friendly, safe, and direct cathode material recycling method for waste lithium-ion batteries. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing an integrated recycling method for waste lithium-ion battery cathode materials and its application. This method utilizes Lewis alkaline active sites on the surface of inorganic fillers to induce a dehydrofluorination reaction in polyvinylidene fluoride (PVDF), achieving efficient separation of the cathode material from the aluminum foil. Simultaneously, in-situ generated hydrofluoric acid (HF) is used to clean the solid electrolyte interface (CEI) layer on the surface of the failed cathode. Then, the remaining inorganic fillers and their derived phases are used in a subsequent sintering process to construct a protective coating layer in one step. This method integrates the three independent steps of separation, cleaning, and coating in traditional recycling processes into a single integrated process, offering advantages such as a shorter process, lower cost, environmental friendliness, and superior performance of the recycled materials.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] An integrated recycling method for waste lithium-ion battery cathode materials, the method comprising the following steps:

[0011] S1. The waste lithium-ion battery positive electrode sheet is crushed to obtain electrode fragments;

[0012] S2. The electrode fragments are mixed with inorganic fillers, a dispersion medium is added, and ultrasonic treatment is performed to obtain a mixed slurry; the surface of the inorganic fillers has Lewis basic active sites, which can induce polyvinylidene fluoride to undergo a dehydrofluorination reaction.

[0013] S3. The mixed slurry is subjected to solid-liquid separation to obtain separated aluminum foil and positive electrode powder;

[0014] S4. Wash and dry the positive electrode powder to obtain pretreated positive electrode powder;

[0015] S5. Add lithium salt to the pretreated cathode powder for lithium compensation, and then sinter in an oxygen-containing atmosphere to obtain a regenerated cathode material.

[0016] The technical principle of this invention is as follows: Lewis basic sites (such as Zr-O) on the surface of inorganic fillers. - La-O - Al-O - Mg-O - (e.g., fluorine atoms) can undergo Lewis acid-base interactions with fluorine atoms in the PVDF molecular chain, weakening the CF bond energy. Under ultrasonic treatment conditions, the cavitation effect generated in the liquid can create local high temperature and high pressure, and produce micro-jet impacts. These physical effects can activate the surface of the inorganic filler, fully exposing the Lewis basic sites; and promote the contact between the PVDF molecular chain and the active sites. Simultaneously, the local energy provided by the cavitation effect facilitates the dehydrofluorination reaction. Under the synergistic effect of the above chemical and physical factors, PVDF undergoes a dehydrofluorination reaction, generating a conjugated olefin structure and releasing HF, causing PVDF to change from a highly viscoelastic state to a brittle state, losing its binding ability, thereby achieving efficient separation of the cathode material from the aluminum foil. At the same time, the HF generated in situ during the PVDF dehydrofluorination process can act on the surface of the failed cathode material, reacting with decomposition products such as organic carbonates and organic lithium salts in the CEI layer, achieving surface cleaning. The residual inorganic filler and its derived phases formed during sintering form a protective coating layer in situ on the cathode material surface, suppressing interfacial side reactions and promoting lithium-ion transport.

[0017] Further, in step S2, the inorganic filler is one or more of garnet oxide, NASICON oxide, perovskite oxide, LiSICON oxide material, metal oxide, metal hydroxide, and layered bimetallic hydroxide; the dispersion medium is one or more of ethanol, γ-valerolactone, phytic acid, and methanol-citric acid composite system.

[0018] Further, in step S2, the garnet-type oxide is LLZO (Li7La3Zr2O). 12 ), LLZTO (Li6.4 La3Zr 1.4 Ta 0.6 O 12 ), LLZNO (Li 6.75 La3Zr 1.75 Nb 0.25 O 12 One or more of the following: ; the NASICON-type oxide is LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) and / or LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO4)3); the perovskite oxide is LLTO (Li 0.5 La 0.5 TiO3); the LiSICON type oxide is Li 14 Zn(GeO4)4, Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP), Li 1.3 Al 0.3 Ge 1.7 (PO4)3(LAGP), Li 4-2x Ge 1-x Mo x One or more of O4; the metal oxide is one or more of MgO, CaO, ZnO, and Al2O3; the metal hydroxide is one or more of lithium hydroxide, sodium hydroxide, and aluminum hydroxide; the layered bimetallic hydroxide is Mg-Al-LDH and / or Zn-Al-LDH.

[0019] Further, in step S2, the particle size of the inorganic filler is 50~500 nm; the mass ratio of the inorganic filler to the positive electrode material in the electrode fragment is 1~10:100.

[0020] Furthermore, in step S2, the ultrasonic treatment power is 100~500 W, the frequency is 20~100 kHz, and the time is 5~60 min.

[0021] Furthermore, in step S4, the detergent used for washing is deionized water and / or anhydrous ethanol; the drying temperature is 60~100℃, and the drying time is 6~24 h.

[0022] Further, in step S5, the sintering temperature is 400~800℃, the sintering time is 2~12 h, and the heating rate is 1~10℃ / min; the oxygen-containing atmosphere is air or oxygen atmosphere.

[0023] Further, in step S5, the lithium salt is one or more of lithium carbonate, lithium hydroxide, and lithium acetate; the amount of lithium salt added is 0.5 to 5% of the mass of the pretreated cathode powder.

[0024] A regenerated cathode material prepared by the above-mentioned integrated regeneration method, wherein the regenerated cathode material is a regenerated lithium nickel cobalt manganese oxide (NCM) ternary cathode material or a regenerated lithium cobalt oxide (LCO) cathode material; the surface of the regenerated cathode material is coated with a coating layer formed by inorganic filler and its derived phase, wherein the thickness of the coating layer is 2~50 nm.

[0025] An application of a regenerated cathode material prepared by the above-mentioned integrated regeneration method in a lithium battery, wherein the lithium battery comprises: a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode contains the regenerated cathode material.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) High separation efficiency and avoidance of toxic organic solvents: This invention utilizes the Lewis basic active sites on the surface of inorganic fillers to induce a dehydrofluorination reaction in PVDF under ultrasonic assistance, transforming it from a highly viscoelastic structure to a brittle conjugated structure, thereby achieving efficient separation of the cathode material and aluminum foil. Compared with the existing technology that uses a large amount of organic solvents such as NMP to dissolve PVDF, this invention uses bio-based or environmentally friendly solvents as the dispersion medium, avoiding the use of toxic solvents such as NMP, eliminating the need for a solvent recovery system, and reducing the environmental load and operating costs of the pretreatment process.

[0028] (2) In-situ cleaning of CEI layer using HF: The HF generated in-situ during the PVDF dehydrofluorination process can clean the CEI layer on the surface of the failed cathode, remove high-resistivity organic carbonates and organic lithium salt components, and improve the lithium-ion transport path. Compared with traditional acid washing or calcination methods, this process does not require additional acid or heating, simplifying the process flow.

[0029] (3) One-step sintering to form a coating layer: The residual inorganic filler and the derived phase formed during the sintering process can form a coating layer in situ on the surface of the regenerated cathode material. This coating layer can suppress the side reactions between the cathode material and the electrolyte and improve cycle stability. Compared with the existing technology that requires the addition of a coating agent and secondary sintering, this method saves additional steps and material costs.

[0030] (4) Short process flow: This invention integrates the three independent steps of separation, CEI cleaning, and coating in the traditional recycling process into a single process, shortening the process chain. Compared with pyrometallurgy, it avoids high-temperature roasting above 1400℃; compared with hydrometallurgy, it avoids the consumption of large amounts of acid and alkali reagents and the treatment of saline wastewater; compared with aluminothermic reduction, it avoids high temperatures above 3000℃ and violent reactions. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the integrated regeneration method in Embodiment 1 of the present invention.

[0032] Figure 2 These are physical images comparing the separation effect of the positive electrode material and aluminum foil in Example 1 (left) and Comparative Example 1 (right) of the present invention.

[0033] Figure 3 These are SEM images of the regenerated cathode materials obtained in Example 1 (left) and Comparative Example 1 (right) of the present invention.

[0034] Figure 4 This is a comparison chart of the cycle performance of batteries assembled from recycled cathode materials in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides an integrated regeneration method for waste NCM83 cathode materials, as detailed in the attached instruction manual. Figure 1 As shown, the specific steps are as follows:

[0038] S1. Cut the waste NCM83 positive electrode sheet (containing NCM83 positive electrode material, PVDF binder and conductive carbon black, and aluminum foil current collector thickness of 12μm) that has been cycle-aged to 80% capacity retention into 2 cm × 2 cm fragments, and weigh 10 g of electrode sheet fragments for later use.

[0039] S2. Mix 0.3 g of LLZTO ceramic powder with a particle size of 200 nm with 10 g of electrode fragments, add 30 mL of anhydrous ethanol as a dispersion medium, and sonicate at 200 W power and 40 kHz frequency for 10 min to obtain a mixed slurry.

[0040] It should be noted that the LLZTO surface has Lewis basic sites (such as Zr-O). - La-O - HF can interact with fluorine atoms in PVDF through Lewis acid-base interactions, weakening the CF bonds. The cavitation effect generated by ultrasonic treatment creates localized high temperature and pressure, activating the LLZTO surface on one hand and promoting contact between the PVDF molecular chains and active sites on the other, providing energy for the dehydrofluorination reaction. Under these synergistic effects, PVDF undergoes dehydrofluorination, generating a conjugated olefin structure and releasing HF, causing PVDF to lose its binding ability, thereby achieving the separation of the cathode material from the aluminum foil (e.g., ...). Figure 2 (As shown).

[0041] S3. Pass the mixed slurry through a 200-mesh sieve to separate the aluminum foil and positive electrode powder. The aluminum foil is collected after rinsing with anhydrous ethanol, and the positive electrode powder is collected for later use. The mass of the separated positive electrode powder is weighed, and the separation rate is calculated to be 94.2%.

[0042] S4. Wash the separated positive electrode powder three times with anhydrous ethanol and dry it in a vacuum drying oven at 80℃ for 12 h to obtain pretreated positive electrode powder.

[0043] S5. Add 3 wt% Li2CO3 to the pretreated cathode powder, mix evenly, and sinter in air atmosphere. The heating rate is 5℃ / min, the sintering temperature is 700℃, the holding time is 4 h, and the material is naturally cooled to room temperature to obtain the regenerated NCM83 cathode material.

[0044] SEM characterization of the recycled cathode material, such as... Figure 3 As shown, the material surface is smooth and clean, with no obvious reactive CEI layer residue.

[0045] Regenerated NCM83 cathode material was mixed with conductive carbon black and PVDF at a mass ratio of 94:3:3, coated onto aluminum foil, dried, and then die-cut into cathode sheets. A CR2032 coin cell was assembled using a lithium sheet as the anode, Celgard 2400 as the separator, and 1 M LiPF6 / EC+DMC (1:1) as the electrolyte. Electrochemical tests were conducted at room temperature, with a voltage range of 2.8–4.3 V. The test results are as follows. Figure 4 As shown, the initial coulombic efficiency of the recycled cathode material at 0.1C rate is 90.6%; after 400 cycles at 0.2C charge and 2C discharge rates, the capacity retention is 80.6%.

[0046] Example 2

[0047] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0048] In step S2, 0.1 g of LLZTO was added (i.e., the mass ratio of LLZTO to the cathode material was 1:100). In step S5, 2 wt% of Li₂CO₃ was added, and the remaining steps were the same as in Example 1. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1C was 89.7%; after 400 cycles at a charge rate of 0.2C and a discharge rate of 2C, the capacity retention was 78.2%.

[0049] Example 3

[0050] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0051] In step S2, 0.5 g of LLZTO was added (i.e., the mass ratio of LLZTO to the cathode material was 5:100). In step S5, 4 wt% of Li₂CO₃ was added, and the remaining steps were the same as in Example 1. The calculated separation rate was 95.8%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 88.5%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 77.1%.

[0052] Example 4

[0053] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0054] In step S2, the ultrasonic treatment time was extended to 30 min. In step S5, 3 wt% Li₂CO₃ was added, and the remaining steps were the same as in Example 1. The calculated separation rate was 96.3%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1C was 88.9%; after 400 cycles at 0.2C charge and 2C discharge rates, the capacity retention was 78.6%.

[0055] Example 5

[0056] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0057] In step S2, the dispersion medium was γ-valerol, and in step S5, 3 wt% Li₂CO₃ was added. The remaining steps were the same as in Example 1. The calculated separation rate was 92.8%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 88.2%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 76.9%.

[0058] Example 6

[0059] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0060] In step S2, LLZTO is replaced with an equal amount of LLZO (Li7La3Zr2O). 12 The particles (particle size 200 nm) were dispersed in phytic acid, and 3 wt% Li₂CO₃ was added in step S5. The remaining steps were the same as in Example 1. The calculated separation rate was 89.5%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 86.5%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 74.3%.

[0061] Example 7

[0062] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0063] In step S2, LLZTO is replaced with an equal amount of LATP (Li 1.3 Al 0.3 Ti 1.7(PO4)3 (particle size 200 nm), dispersed in a methanol-citric acid composite system (methanol to citric acid mass ratio 10:1), ultrasonically treated for 20 min, with 3 wt% Li2CO3 added in step S5, and the remaining steps being the same as in Example 1. The calculated separation rate was 88.3%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 85.9%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 73.5%.

[0064] Example 8

[0065] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0066] In step S2, LLZTO was replaced with an equal amount of MgO (particle size 200 nm), the dispersion medium was anhydrous ethanol, and the ultrasonic treatment time was 10 min. In step S5, 3 wt% Li2CO3 was added, and the remaining steps were the same as in Example 1. The calculated separation rate was 91.8%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 88.1%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 78.3%.

[0067] Example 9

[0068] This embodiment provides an integrated regeneration method for waste NCM83 cathode material. Steps identical or corresponding to those in Embodiment 1 are numbered as in Embodiment 1. For simplicity, only the differences from Embodiment 1 are described below. The differences between this embodiment and Embodiment 1 are as follows:

[0069] In step S2, LLZTO was replaced with an equal amount of metal hydroxide Al(OH)3 (particle size 200 nm), the dispersion medium was anhydrous ethanol, and the ultrasonic treatment time was 10 min. In step S5, 3 wt% Li2CO3 was added, and the remaining steps were the same as in Example 1. The calculated separation rate was 90.5%. Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 87.3%; after 400 cycles at 0.2 C charge and 2 C discharge rates, the capacity retention was 77.2%.

[0070] Comparative Example 1 (without inorganic fillers)

[0071] This comparative example provides a comparative method without adding inorganic fillers. The remaining steps are the same as in Example 1, and the specific steps are as follows:

[0072] S1. Cut the waste NCM83 positive electrode sheet that has been cycled and aged to 80% capacity retention into 2 cm × 2 cm fragments, and weigh 10 g of electrode sheet fragments.

[0073] S2. Add 10 g of electrode fragments to 30 mL of anhydrous ethanol and sonicate at 200 W power and 40 kHz frequency for 60 min (extend the treatment time) to obtain a mixed slurry.

[0074] S3. Pass the mixed slurry through a 200-mesh sieve to separate the aluminum foil and positive electrode powder. The calculated separation rate was 45.3%, with a large amount of positive electrode material remaining on the aluminum foil surface. SEM observation showed that after extending the ultrasonic treatment time to 60 min, the morphology of the residual positive electrode material on the aluminum foil surface was similar to that of Example 1 with only 10 min of treatment, but the separation rate was still much lower than that of Example 1.

[0075] S4. Wash the separated positive electrode powder three times with anhydrous ethanol and dry it in a vacuum drying oven at 80℃ for 12 h to obtain pretreated positive electrode powder.

[0076] S5. Add 3 wt% Li2CO3 to the pretreated cathode powder, mix evenly, and sinter in air atmosphere. The heating rate is 5℃ / min, the sintering temperature is 700℃, the holding time is 4 h, and the material is naturally cooled to room temperature to obtain the regenerated NCM83 cathode material.

[0077] Electrochemical testing results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1 C rate was 88.3%; after 200 cycles at 0.2 C charge and 2 C discharge rates (only 200 cycles were completed due to rapid capacity decay), the capacity retention rate was 68.9%. Compared with Example 1, Comparative Example 1, due to the lack of inorganic filler, resulted in insufficient PVDF dehydrofluorination reaction, poor separation effect, and a significant decrease in the cycling performance of the regenerated material.

[0078] Comparative Example 2 (Traditional NMP Separation Method)

[0079] This comparative example provides a method for treating waste NCM83 cathode material using a traditional NMP dissolution and separation method. The remaining steps are the same as in Example 1, and the specific steps are as follows:

[0080] S1. Cut the waste NCM83 positive electrode sheet that has been cycled and aged to 80% capacity retention into 2 cm × 2 cm fragments, and weigh 10 g of electrode sheet fragments.

[0081] S2. Add the electrode fragments to 100 mL of NMP and stir at 80°C for 2 h to dissolve the PVDF completely, thus separating the positive electrode material from the aluminum foil.

[0082] S3. Filter to separate aluminum foil and positive electrode material. The positive electrode material is washed three times with NMP and then three times with anhydrous ethanol. It is then dried in a vacuum drying oven at 80℃ for 12 h to obtain pretreated positive electrode powder. The calculated separation rate is 98.5%.

[0083] S4. Add 3 wt% Li2CO3 to the pretreated cathode powder, mix evenly, and sinter in air atmosphere. The heating rate is 5℃ / min, the sintering temperature is 700℃, the holding time is 4 h, and the material is naturally cooled to room temperature to obtain the regenerated NCM83 cathode material.

[0084] Electrochemical test results showed that the initial coulombic efficiency of the regenerated cathode material at 0.1C was 82.5%; after 400 cycles at 0.2C charge and 2C discharge rates, the capacity retention was 64.6%. Compared with Example 1, Comparative Example 2 used a large amount of NMP solvent in the separation process, and the electrochemical performance of the regenerated material was significantly lower than that of Example 1.

[0085] Comparative Example 3 (Inert filler SiO2)

[0086] This comparative example provides a comparative method using inert filler SiO2. The remaining steps are the same as in Example 1, and the specific steps are as follows:

[0087] S1. Cut the waste NCM83 positive electrode sheet that has been cycled and aged to 80% capacity retention into 2 cm × 2 cm fragments, and weigh 10 g of electrode sheet fragments.

[0088] S2. Mix 0.3 g of SiO2 nanoparticles with a particle size of 200 nm with 10 g of electrode fragments, add 30 mL of anhydrous ethanol as a dispersion medium, and sonicate at 200 W power and 40 kHz frequency for 30 min to obtain a mixed slurry.

[0089] S3. Pass the mixed slurry through a 200-mesh sieve to separate the aluminum foil and positive electrode powder. The calculated separation rate is 52.1%. The collected positive electrode powder contains some coarse particles that have not been detached and aluminum shavings.

[0090] S4. Wash the separated positive electrode powder three times with anhydrous ethanol and dry it in a vacuum drying oven at 80℃ for 12 h to obtain pretreated positive electrode powder.

[0091] S5. Add 3 wt% Li2CO3 to the pretreated cathode powder, mix evenly, and sinter in air atmosphere. The heating rate is 5℃ / min, the sintering temperature is 700℃, the holding time is 4 h, and the material is naturally cooled to room temperature to obtain the regenerated NCM83 cathode material.

[0092] Electrochemical test results showed that the initial coulombic efficiency at 0.1 C rate was only 71.2%; at 0.2 C charge and 2 C discharge rates, the capacity retention after 150 cycles was 60.5% (below 50% after 200 cycles), failing to complete an effective cycle of 400 cycles. Compared with Example 1, Comparative Example 3 used SiO2 filler without Lewis basic sites on its surface, which could not effectively induce PVDF dehydrofluorination, resulting in incomplete separation. Furthermore, the residual inert SiO2 particles and aluminum shavings formed impurity phases after sintering, severely degrading the electrochemical performance of the recycled material. Its initial efficiency and cycle stability were significantly lower than those of Example 1, and also inferior to Comparative Example 1, which had no filler but extended ultrasonic time.

[0093] Comparison table of process and performance between Examples 1-7 and Comparative Examples 1-3

[0094]

[0095] Note 1: Comparative Example 1 was only tested up to 200 cycles due to its faster cycle performance degradation.

[0096] Note 2: Comparative Example 3 had a capacity retention rate of less than 50% after 200 cycles, making it impossible to complete 400 cycles. Therefore, only data from 150 cycles are listed.

[0097] The above comparison shows that the integrated regeneration method of the present invention, while ensuring a high separation rate (>85%), significantly improves the electrochemical performance of the regenerated cathode material through in-situ HF cleaning of CEI and filler-derived phase coating, combined with lithium supplementation sintering. The initial coulombic efficiency of Examples 1-7 all reached over 85%, and the capacity retention rate after 400 cycles was all above 73%, with Example 1 showing the best performance (initial coulombic efficiency 90.6%, 400-cycle retention rate 80.6%). Comparative Example 1, due to the lack of inorganic filler, had a low separation rate and significantly reduced cycle performance; Comparative Example 2, using the traditional NMP method, had a high separation rate but poor regenerated material performance; Comparative Example 3, using inert SiO2 filler, could not effectively induce PVDF defluorination, resulting in unsatisfactory separation and electrochemical performance.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated regeneration method for waste lithium-ion battery cathode materials, characterized in that: The method includes the following steps: S1. The waste lithium-ion battery positive electrode sheet is crushed to obtain electrode fragments; S2. Mix the electrode fragments with inorganic fillers, add a dispersion medium, and perform ultrasonic treatment to obtain a mixed slurry; S3. The mixed slurry is subjected to solid-liquid separation to obtain separated aluminum foil and positive electrode powder; S4. Wash and dry the positive electrode powder to obtain pretreated positive electrode powder; S5. Add lithium salt to the pretreated cathode powder for lithium compensation, and then sinter in an oxygen-containing atmosphere to obtain a regenerated cathode material.

2. The integrated regeneration method according to claim 1, characterized in that: In step S2, the inorganic filler is one or more of the following: garnet oxide, NASICON oxide, perovskite oxide, LiSICON oxide material, metal oxide, metal hydroxide, and layered bimetallic hydroxide; the dispersion medium is one or more of the following: ethanol, γ-valerolactone, phytic acid, and methanol-citric acid composite system.

3. The integrated regeneration method according to claim 2, characterized in that: In step S2, the garnet-type oxide is LLZO (Li7La3Zr2O). 12 ), LLZTO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ), LLZNO (Li 6.75 La3Zr 1.75 Nb 0.25 O 12 One or more of the following: ; the NASICON-type oxide is LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3) and / or LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO4)3); the perovskite oxide is LLTO (Li 0.5 La 0.5 TiO3); the LiSICON type oxide is Li 14 Zn(GeO4)4, Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP), Li 1.3 Al 0.3 Ge 1.7 (PO4)3(LAGP), Li 4-2x Ge 1-x Mo x One or more of O4; the metal oxide is one or more of MgO, CaO, ZnO, and Al2O3; the metal hydroxide is one or more of lithium hydroxide, sodium hydroxide, and aluminum hydroxide; the layered bimetallic hydroxide is Mg-Al-LDH and / or Zn-Al-LDH.

4. The integrated regeneration method according to claim 1, characterized in that: In step S2, the particle size of the inorganic filler is 50~500 nm; the mass ratio of the inorganic filler to the positive electrode material in the electrode fragment is 1~10:

100.

5. The integrated regeneration method according to claim 1, characterized in that: In step S2, the ultrasonic treatment power is 100~500 W, the frequency is 20~100 kHz, and the time is 5~60 min.

6. The integrated regeneration method according to claim 1, characterized in that: In step S4, the detergent used for washing is deionized water and / or anhydrous ethanol; the drying temperature is 60~100℃ and the drying time is 6~24 h.

7. The integrated regeneration method according to claim 1, characterized in that: In step S5, the sintering temperature is 400~800℃, the sintering time is 2~12 h, and the heating rate is 1~10℃ / min; the oxygen-containing atmosphere is air or oxygen atmosphere.

8. The integrated regeneration method according to claim 1, characterized in that: In step S5, the lithium salt is one or more of lithium carbonate, lithium hydroxide, and lithium acetate; the amount of lithium salt added is 0.5 to 5% of the mass of the pretreated cathode powder.

9. A regenerated cathode material prepared by the integrated regeneration method according to any one of claims 1 to 8, characterized in that: The regenerated cathode material is a regenerated lithium nickel cobalt manganese oxide (NCM) ternary cathode material or a regenerated lithium cobalt oxide (LCO) cathode material; the surface of the regenerated cathode material is coated with a coating layer formed by inorganic fillers and their derived phases, and the thickness of the coating layer is 2~50 nm.

10. The application of a regenerated cathode material prepared by the integrated regeneration method according to any one of claims 1 to 8 in a lithium battery, characterized in that: The lithium battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode contains the recycled positive electrode material.

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