Catalyst preparation method based on retired lithium cobalt oxide battery cathode material and its application in water electrolysis.

Abstract

This invention relates to the fields of resource recycling and high-value utilization technology and catalyst preparation technology, particularly to a method for preparing a catalyst based on the positive electrode material of a retired lithium cobalt oxide battery and its application in water electrolysis. The catalyst preparation method includes the following steps: (a) charging the retired lithium cobalt oxide battery at a constant current at high temperature to a target voltage, and then maintaining the voltage at the target voltage for more than 6 hours; (b) disassembling the retired lithium cobalt oxide battery, collecting the lithium cobalt oxide material from the positive electrode portion, grinding it, and obtaining the catalyst; the target voltage is higher than the charging cutoff voltage of the retired lithium cobalt oxide battery. The method of this invention, while increasing the defect density and enriching the active sites of the catalyst, promotes structural evolution, effectively avoids structural collapse, and significantly improves the catalytic activity and long-term catalytic stability of the prepared catalyst in the oxygen evolution reaction of water electrolysis.

Description

Technical Field

[0001] This invention relates to the fields of resource recycling and high-value utilization technology and catalyst preparation technology, and in particular to a catalyst preparation method based on retired lithium cobalt oxide battery cathode material and its application in water electrolysis. Background Technology

[0002] With the widespread application of lithium-ion batteries in consumer electronics, lithium cobalt oxide batteries have become a mainstream choice due to their high energy density and stable performance. However, the resource waste and environmental problems caused by their large-scale retirement are becoming increasingly serious. Statistics show that lithium cobalt oxide batteries account for more than 40% of retired lithium batteries generated globally each year. Traditional recycling technologies include pyrometallurgy and hydrometallurgy. The former is energy-intensive and prone to producing harmful gases, while the latter has complex processes and is difficult to treat waste liquid. Furthermore, although these methods can partially extract cobalt resources, they are difficult to utilize at high value and generally involve lithium loss and secondary pollution risks during the recycling process.

[0003] Meanwhile, hydrogen production via water electrolysis, a key component of clean energy technology, suffers from slow oxygen evolution reaction (OER) kinetics, necessitating the development of highly efficient catalysts to reduce overpotential and energy consumption. Cobalt-based materials (such as cobalt tetroxide and cobalt hydroxyl oxide) have attracted considerable attention due to their excellent catalytic activity; however, the preparation of these materials relies on newly mined cobalt resources, resulting in high costs and unsustainability.

[0004] Against this backdrop, if the cobalt resources in retired lithium cobalt oxide batteries can be recycled and converted into high-performance OER catalysts, it will not only alleviate the resource waste and environmental pressure caused by retired batteries from the source, but also provide a low-cost and sustainable catalyst supply path for hydrogen production by water electrolysis, realizing the high-value utilization of retired lithium cobalt oxide battery resources.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a catalyst based on retired lithium cobalt oxide battery cathode material and its application in water electrolysis. The method of this invention achieves low-cost and environmentally friendly recycling of retired lithium cobalt oxide battery cathode material and provides it with a high-value utilization pathway. The prepared catalyst exhibits excellent catalytic performance in the oxygen evolution reaction of alkaline water electrolysis.

[0007] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a method for preparing a catalyst based on a retired lithium cobalt oxide battery cathode material, comprising the following steps: (a) Charge the retired lithium cobalt oxide battery at a constant current at high temperature to the target voltage, and then maintain the voltage at the target voltage for more than 6 hours; (b) Disassemble the retired lithium cobalt oxide battery after step (a), collect the lithium cobalt oxide material in the positive electrode part, grind it to obtain the catalyst; The target voltage is higher than the charging cutoff voltage of the retired lithium cobalt oxide battery.

[0008] Furthermore, the high temperature is 50–60°C.

[0009] Furthermore, the duration of the voltage holding is 6 to 12 hours.

[0010] Furthermore, the nominal voltage of the retired lithium cobalt oxide battery is 3.7 to 3.8 V, and the charging cut-off voltage of the retired lithium cobalt oxide battery is 4.2 to 4.4 V.

[0011] Furthermore, the target voltage is 4.2–5 V, preferably 4.5–5 V.

[0012] Furthermore, in the constant current charging, the current is 0.01 to 0.5 C.

[0013] Furthermore, during the voltage maintenance process, the decommissioned lithium cobalt oxide battery is charged with a current of ≤0.5 C to maintain the voltage at the target voltage.

[0014] Furthermore, the collection of the lithium cobalt oxide material from the positive electrode portion includes: immersing the disassembled positive electrode portion in an organic solvent to separate the lithium cobalt oxide material, and then washing and drying the lithium cobalt oxide material.

[0015] The second aspect of the present invention provides a catalyst prepared by the catalyst preparation method based on retired lithium cobalt oxide battery cathode material provided in the first aspect of the present invention.

[0016] Furthermore, the catalyst has a micron-scale layered structure.

[0017] Furthermore, the average particle size of the catalyst is 2 μm ± 0.2 μm.

[0018] The third aspect of the present invention provides the application of the catalyst of the second aspect of the present invention in the oxygen evolution reaction of water electrolysis.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention achieves precise deep delithiation and controllable structural reconstruction of the cathode material of retired lithium cobalt oxide batteries by performing high-pressure holding treatment at high temperature. This process induces a large number of oxygen vacancies and various defects in the material by electrochemically overcharging to the target high voltage at high temperature, thereby significantly improving the density of active sites. Combined with high temperature and low current voltage holding treatment, it promotes the transformation of the material to a thermodynamically stable state while inducing the orderly evolution of vacancies and defects. The catalyst obtained thereby improves the defect density and enriches the active sites while effectively avoiding structural collapse, thus significantly improving its intrinsic catalytic activity and long-term catalytic stability in the oxygen evolution reaction of water electrolysis. (2) The preparation method of the present invention is simple and controllable. It only requires adjusting the temperature, the target charging voltage, and the holding voltage time. It does not require complicated post-processing, is low in cost, and is environmentally friendly. Furthermore, the method of the present invention is compatible with various existing battery charging and discharging systems and is easy to scale up for production. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 Electrochemical LSV curves of materials provided in different embodiments and comparative examples of the present invention; Figure 2 This is a photograph of the disassembled retired lithium cobalt oxide battery after processing, as shown in Embodiment 2 of the present invention. Figure 3 XRD comparison images of the materials provided in Examples 1-3 and Comparative Example 2 of this invention; Figure 4 A scanning electron microscope image of the material provided in Embodiment 2 of the present invention; Figure 5 Transmission electron microscope (TEM) image of the material provided in Embodiment 2 of the present invention; Figure 6 This is a transmission electron microscope (TEM) image of the material provided in Embodiment 4 of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0023] Electrochemical treatment of lithium cobalt oxide batteries is a rapid method to transform lithium cobalt oxide materials into catalysts. However, current electrochemical recycling methods typically only target the cathode material of lithium cobalt oxide batteries for delithiation, limiting their operation to the battery's charging cutoff voltage. The inventors of this invention discovered that the stability of delithiated materials significantly decreases when retired lithium cobalt oxide batteries are overcharged. Specifically, under high-voltage overcharge, the instability of lattice oxygen easily induces local lattice collapse and atomic layer dislocations, resulting in a large number of oxygen vacancies and various structural defects. While this process can expose more active sites and endow the material with potentially high catalytic activity, the ensuing structural collapse severely limits its application. Based on this, this invention proposes a novel process: after high-voltage deep delithiation of retired lithium cobalt oxide batteries, temperature control and low-current voltage maintenance are combined to induce and precisely control the evolution of defects and vacancies, gradually transforming them into thermodynamically stable structures. This achieves a balance between high defect density and structural stability, resulting in long-term, high-efficiency catalytic performance. This method not only effectively applies defect engineering but also opens up a new avenue for the high-value utilization of retired lithium cobalt oxide batteries.

[0024] The first aspect of this invention provides a method for preparing a catalyst based on a retired lithium cobalt oxide battery cathode material, comprising the following steps: (a) Charge the retired lithium cobalt oxide battery at a constant current at high temperature to the target voltage, and then maintain the voltage at the target voltage for more than 6 hours; (b) Disassemble the retired lithium cobalt oxide battery after step (a), collect the lithium cobalt oxide material in the positive electrode part, grind it to obtain a catalyst; The target voltage is higher than the charging cutoff voltage of retired lithium cobalt oxide batteries.

[0025] In the preparation method of this invention, a high-temperature, high-pressure, and pressure-holding process is used to deeply delithigate the lithium cobalt oxide battery cathode material, inducing a high-density complex defect network (Li vacancies, oxygen vacancies, lattice distortion, and stacking fault synergy), significantly increasing the active sites of the material. On the other hand, temperature control promotes the material's transition to a thermodynamically stable state, and a low-current pressure-holding process at the target voltage induces the ordered evolution of vacancies and defects. Through this multi-faceted synergy, while increasing defect density and enriching active sites, structural collapse is effectively avoided, significantly improving the catalytic activity and long-term catalytic stability of the obtained catalyst in the oxygen evolution reaction of water electrolysis.

[0026] Furthermore, this invention uses low-cost retired lithium cobalt oxide batteries as raw materials and directly converts them into a highly efficient alkaline water electrolysis oxygen evolution reaction catalyst in one step. This not only achieves efficient and green recycling of retired lithium cobalt oxide batteries, which aligns with the current themes of carbon reduction and sustainable development, but also opens up new application paths for their high-value utilization.

[0027] The operation of this invention is compatible with various battery charging and discharging systems and is easy to scale up for production. In the embodiments shown below, the NEWA battery cabinet "WGDW series (automatic fire extinguishing and explosion-proof type)" is used as an example only as the charging and discharging environment, and the NEWA battery testing equipment NEWA BTS8.0.1 (64-bit) software version is used.

[0028] In a specific embodiment of the present invention, the retired lithium cobalt oxide batteries may be derived from mobile phones, digital cameras, laptops, power banks, etc., and are not limited thereto.

[0029] In a specific embodiment of the present invention, the nominal voltage of the retired lithium cobalt oxide battery is 3.7 to 3.8 V, for example, it can be a range of 3.7 V, 3.72 V, 3.75 V, 3.78 V, 3.8 V or any two of them; the charging cut-off voltage of the retired lithium cobalt oxide battery is 4.2 to 4.4 V, for example, it can be a range of 4.2 V, 4.25 V, 4.3 V, 4.35 V, 4.4 V or any two of them.

[0030] Retired lithium cobalt oxide batteries are those that have met retirement conditions after a period of use. These retirement conditions include safety and electrical performance. It should be noted that, in this invention, retired lithium cobalt oxide batteries refer to those whose rated capacity has decreased to below 80% of their initial nominal capacity, at which point they are retired.

[0031] In a specific embodiment of the present invention, the high temperature is 50–60°C, for example, it can be a range of 50°C, 52°C, 55°C, 58°C, 60°C, or any combination thereof. The charging and holding voltage temperatures in step (a) of the present invention can each be independently selected from 50–60°C. Controlling the temperature within the above range is more conducive to ensuring a balance between deep delithiation of the lithium cobalt oxide cathode material and controllable structural reconstruction. When the temperature is too low, not only is the degree of delithiation low, but the temperature is also insufficient to allow the material to transition to a thermodynamically stable state; when the temperature is too high, it will exacerbate the structural collapse of the material, making it difficult to reconstruct a stable defect structure with high catalytic activity.

[0032] In a specific embodiment of the present invention, the constant current charging current is 0.01–0.5 C, for example, it can be a range of 0.01 C, 0.05 C, 0.1 C, 0.2 C, 0.3 C, 0.4 C, 0.5 C, or any combination thereof. Regulating the constant current charging current within the above range helps maintain the integrity of the material's main structure, providing a basis for the subsequent reconstruction and evolution of internal defects in the material. When the current is too high, lithium ions rapidly and massively escape, causing a sharp increase in lattice stress and leading to structural collapse; when the current is too low, it is detrimental to improving production efficiency.

[0033] In a specific embodiment of the present invention, the target voltage is 4.2–5 V, for example, it can be a range of 4.2 V, 4.3 V, 4.4 V, 4.45 V, 4.5 V, 4.55 V, 4.6 V, 4.65 V, 4.7 V, 4.75 V, 4.8 V, 4.9 V, 5 V, or any combination thereof, preferably 4.5–5 V. A suitable target voltage is more conducive to achieving a balance between high defect density and structural stability. When the target voltage is too low, the induction of high active sites (such as vacancy defects, atomic misalignments, etc.) is insufficient, resulting in low defect density and insufficient number of active sites; when the target voltage is too high, excessive delithiation will occur, and the resulting structure will undergo irreversible collapse, leading to poor structural stability and hindering the catalytic process.

[0034] In a specific embodiment of the present invention, the holding voltage is maintained for 6 to 24 hours, for example, within a range of 6 hours, 8 hours, 12 hours, 16 hours, 20 hours, 24 hours, or any combination thereof. When the holding voltage is insufficient, the ordered evolution of vacancies and defects cannot be induced, resulting in low defect density and poor catalytic activity. When the holding voltage is too long, it not only affects production efficiency but may also lead to further structural collapse, further reduction in interatomic spacing, and transformation from the original O3 phase into more inert rock salt and spinel phases, thereby reducing the efficiency and stability of the catalyst.

[0035] In a specific embodiment of the present invention, during the voltage maintenance process, the decommissioned lithium cobalt oxide battery is charged with a current of ≤0.5 C to maintain the voltage of the decommissioned lithium cobalt oxide battery at the target voltage.

[0036] In practice, once the retired lithium cobalt oxide battery has been charged to the target voltage using a constant current, charging is stopped. Due to battery self-discharge, the battery voltage will decrease over time. After stopping charging for 5–10 seconds, the retired lithium cobalt oxide battery is charged again with a current of ≤0.5 C until the target voltage is reached, at which point charging is stopped. This completes one cycle; this cycle is repeated until the voltage is maintained for more than 6 hours.

[0037] In a specific embodiment of the present invention, maintaining the voltage at the target voltage for 6 hours or more includes: (S1) After stopping charging the battery for 5 to 10 seconds, charge it to the target voltage at a current of 0.01 to 0.5 C, and then stop charging; (S2) Repeat step (S1) until the battery maintains a voltage of more than 6 hours at the target voltage.

[0038] In different embodiments, the current in step (S1) can be within the range of 0.01 C, 0.05 C, 0.1 C, 0.2 C, 0.3 C, 0.4 C, 0.5 C, or any combination thereof. By cyclically charging under high temperature and low current conditions while maintaining the voltage, the orderly evolution of vacancies and defects can be induced, thereby avoiding structural collapse while maintaining high defect density and abundant active sites, significantly improving the stability and long-term catalytic performance of the catalyst.

[0039] In practice, the above operations can be completed using the battery charging and discharging system through conventional settings, and will not be elaborated upon here.

[0040] This invention, through temperature regulation combined with a low-current voltage maintenance method, can induce and precisely control the evolution of defects and vacancies, gradually transforming them into thermodynamically stable structures. This achieves both high defect density and structural stability, resulting in long-term and highly efficient catalytic performance.

[0041] In a specific embodiment of the present invention, after completing step (a), the retired lithium cobalt oxide battery is directly disassembled without discharge treatment.

[0042] In a specific embodiment of the present invention, collecting the lithium cobalt oxide material of the positive electrode portion includes: immersing the disassembled positive electrode portion in an organic solvent to separate the lithium cobalt oxide material, and then washing and drying the lithium cobalt oxide material.

[0043] In specific embodiments of the present invention, the organic solvent includes, but is not limited to, at least one of ethanol, isopropanol, N-methylpyrrolidone, and acetone. The amount of organic solvent used is not limited, as long as it completely immerses the positive electrode portion.

[0044] In a specific embodiment of the present invention, the organic solvent includes isopropanol and N-methylpyrrolidone. Further, the volume ratio of isopropanol to N-methylpyrrolidone is 1:(0.1 to 10).

[0045] In a specific embodiment of the present invention, the soaking time is 1 to 24 hours, for example, it can be a range of 1 hour, 2 hours, 6 hours, 10 hours, 12 hours, 16 hours, 20 hours, 24 hours or any combination thereof; the soaking temperature is 30 to 60 degrees Celsius, for example, it can be a range of 30 degrees Celsius, 35 degrees Celsius, 40 degrees Celsius, 45 degrees Celsius, 50 degrees Celsius, 55 degrees Celsius, 60 degrees Celsius or any combination thereof.

[0046] In a specific embodiment of the present invention, ultrasonication or stirring is performed during the soaking process. The duration of ultrasonication and stirring is not limited, as long as the lithium cobalt oxide material is detached from the positive electrode current collector.

[0047] In a specific embodiment of the present invention, after soaking, lithium cobalt oxide material can be obtained by separation methods such as filtration or centrifugation.

[0048] In a specific embodiment of the present invention, washing includes water washing and / or ethanol washing. Further, the separated lithium cobalt oxide material can be washed with water first, and then washed with ethanol. The number of water washings and ethanol washings is not limited; for example, each can be independently selected from 1 to 5 times.

[0049] In a specific embodiment of the present invention, the drying temperature is 50-60°C and the drying time is 12-24 h.

[0050] In a specific embodiment of the present invention, the grinding process includes ball milling.

[0051] In a specific embodiment of the present invention, the ball-to-material ratio in the ball mill is (50-200):1, for example, it can be a range of 50:1, 80:1, 100:1, 120:1, 150:1, 180:1, 200:1 or any combination thereof.

[0052] In a specific embodiment of the present invention, N-methylpyrrolidone is used as the ball milling medium during ball milling. Further, the ratio of lithium cobalt oxide material to ball milling medium is 1 g: (10-20) mL. For example, the amount of ball milling medium used per 1 g of lithium cobalt oxide material to be ball milled can be 10 mL, 12 mL, 15 mL, 18 mL, 20 mL, or any combination thereof.

[0053] In a specific embodiment of the present invention, the ball milling speed is 300 to 500 rpm, for example, it can be a range of 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm or any combination thereof.

[0054] In a specific embodiment of the present invention, the method further includes washing and drying the ball-milled material. The washing and drying operations can be referenced from the washing and drying operations after separating lithium cobalt oxide material, and will not be described in detail here.

[0055] The second aspect of the present invention provides a catalyst prepared by the catalyst preparation method based on retired lithium cobalt oxide battery cathode material provided in the first aspect of the present invention.

[0056] In a specific embodiment of the present invention, the catalyst has a micron-scale layered structure. The catalyst obtained by the method of the present invention has a micron-scale layered structure, exhibiting a high specific surface area and abundant active sites.

[0057] In a specific embodiment of the present invention, the average particle size of the catalyst is 2 μm ± 0.2 μm, for example, it can be a range of 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm or any combination thereof.

[0058] The third aspect of the present invention provides the application of the catalyst of the second aspect of the present invention in the oxygen evolution reaction of water electrolysis.

[0059] The retired lithium cobalt oxide battery used in the following specific embodiments of the present invention is a soft-pack battery used in toys. The soft-pack battery is from Xi'an Jingwei Energy Electronic Technology Co., Ltd., model PL404048-950 mAh, rated capacity of 950 mAh, and nominal voltage of 3.7 V.

[0060] Example 1 This embodiment provides a catalyst preparation method based on retired lithium cobalt oxide battery cathode material, including the following steps: (1) The retired lithium cobalt oxide battery is charged to 4.2 V at a constant current of 0.5 C at 60°C and held at 4.2 V for 12 h at 60°C; wherein, holding at 4.2 V for 12 h includes: after the battery voltage reaches 4.2 V, stopping charging for 10 s, and then charging to 4.2 V at a constant current of 0.1 C; repeating the above operation until the battery holds at a voltage of around 4.2 V for 12 h.

[0061] (2) The battery treated in step (1) is not discharged. The positive electrode part is directly disassembled and immersed in N-methylpyrrolidone and isopropanol at 30°C with a volume ratio of 1:1 for 6 h. During the immersion, ultrasonic treatment is performed for about 1 h. The lithium cobalt oxide material is obtained by centrifugation. The lithium cobalt oxide material is washed with water 3 times and ethanol 3 times, and then dried in an oven at 60°C for 24 h. The material is collected.

[0062] (3) Weigh the material obtained in step (2) and N-methylpyrrolidone at a ratio of 1 g: 15 mL, add them to a ball mill, and ball mill at 500 rpm for 24 h at a ball-to-material ratio of 100:1 (using zirconium bead ball milling). Collect the ball-milled material, wash it with water 3 times and with ethanol 3 times, and then dry it in an oven at 60℃ for 24 h to obtain the catalyst.

[0063] Example 2 This embodiment provides a catalyst preparation method based on retired lithium cobalt oxide battery cathode material, including the following steps: (1) The retired lithium cobalt oxide battery is charged to 4.5 V at a constant current of 0.5 C at 60°C and held at 4.5 V for 12 h at 60°C; wherein, holding at 4.5 V for 12 h includes: after the battery voltage reaches 4.5 V, stopping charging for 10 s, and then charging to 4.5 V at a constant current of 0.1 C; repeating the above operation until the battery holds at a voltage of around 4.5 V for 12 h.

[0064] (2) The battery treated in step (1) is not discharged. The positive electrode part is directly disassembled and immersed in N-methylpyrrolidone and isopropanol at 30°C with a volume ratio of 1:1 for 6 h. During the immersion, ultrasonic treatment is performed for about 1 h. The lithium cobalt oxide material is obtained by centrifugation. The lithium cobalt oxide material is washed with water 3 times and ethanol 3 times, and then dried in an oven at 60°C for 24 h. The material is collected.

[0065] (3) Weigh the material obtained in step (2) and N-methylpyrrolidone at a ratio of 1 g: 15 mL, add them to a ball mill, and ball mill at 500 rpm for 24 h at a ball-to-material ratio of 100:1 (using zirconium bead ball milling). Collect the ball-milled material, wash it with water 3 times and with ethanol 3 times, and then dry it in an oven at 60℃ for 24 h to obtain the catalyst.

[0066] Example 3 This embodiment provides a catalyst preparation method based on retired lithium cobalt oxide battery cathode material, including the following steps: (1) The retired lithium cobalt oxide battery is charged to 4.8 V at a constant current of 0.5 C at 60°C and held at 4.8 V for 12 h at 60°C; wherein, holding at 4.8 V for 12 h includes: after the battery voltage reaches 4.8 V, stopping charging for 10 s, and then charging to 4.8 V at a constant current of 0.1 C; repeating the above operation until the battery holds at a voltage of around 4.8 V for 12 h.

[0067] (2) The battery treated in step (1) is not discharged. The positive electrode part is directly disassembled and immersed in N-methylpyrrolidone and isopropanol at 30°C with a volume ratio of 1:1 for 6 h. During the immersion, ultrasonic treatment is performed for about 1 h. The lithium cobalt oxide material is obtained by centrifugation. The lithium cobalt oxide material is washed with water 3 times and ethanol 3 times, and then dried in an oven at 60°C for 24 h. The material is collected.

[0068] (3) Weigh the material obtained in step (2) and N-methylpyrrolidone at a ratio of 1 g: 15 mL, add them to a ball mill, and ball mill at 500 rpm for 24 h at a ball-to-material ratio of 100:1 (using zirconium bead ball milling). Collect the ball-milled material, wash it with water 3 times and with ethanol 3 times, and then dry it in an oven at 60℃ for 24 h to obtain the catalyst.

[0069] Example 4 This embodiment refers to the preparation method of Embodiment 2, the only difference being: in step (1), the duration of holding the voltage at 4.5 V is different, the specific difference is as follows: In this embodiment, the voltage is maintained at 4.5 V for 24 hours.

[0070] Comparative Example 1 Comparative Example 1 uses the same preparation method as Example 1, except that step (1) is different.

[0071] Step (1) of Comparative Example 1 includes: charging the retired lithium cobalt oxide battery at a constant current of 0.5 C to 4.5 V at 30°C, and then terminating the charging.

[0072] Comparative Example 2 Comparative Example 2 uses the same preparation method as Example 1, except that step (1) is different.

[0073] Step (1) of Comparative Example 2 includes: the retired lithium cobalt oxide battery is disassembled directly without charging.

[0074] Comparative Example 3 Comparative Example 3 follows the same preparation method as Example 2, except that the duration of holding the voltage at 4.5 V in step (1) is different. The specific differences are as follows: In Comparative Example 3, the voltage was maintained at 4.5 V for 0 h.

[0075] Experimental Example Electrochemical tests were performed on the materials obtained from different embodiments and comparative examples. The test scenario was an alkaline water electrolysis oxygen evolution reaction. All materials were tested under the same conditions. The specific test methods are as follows, and the test results are as follows. Figures 1-2 As shown: The material was prepared at 2 mg / cm 2 The electrode was loaded onto carbon paper, and the electrolyte was 1 mol / L potassium hydroxide. Ag / AgCl and carbon rod were used as the reference electrode and counter electrode, respectively. The scan rate of LSV test was 2 mV / s, and the automatic compensation was 85%.

[0076] Figure 1 Table 1 shows the electrochemical LSV curves of the materials provided in different embodiments and comparative examples of the present invention at 10 mA / cm². 2 Overpotential at current density and at 10 mA / cm 2 The material's stable operating time was obtained from a chronopotential stability test at current density. Figure 1 As shown in Table 1, the electrochemical performance of the materials provided in different embodiments and comparative examples varies considerably. Comparative Example 2, serving as a control sample of decommissioned lithium cobalt oxide without high-temperature charging treatment, exhibits a performance of 10 mA / cm². 2 The position has the largest overpotential and the shortest stable operating time, indicating that it requires a larger start-up potential in the alkaline oxygen evolution reaction. Its catalytic performance is poor and its efficiency is low, making it unsuitable as a catalyst for the alkaline water electrolysis oxygen evolution reaction.

[0077] Based on the overpotential and stability time data of Examples 1-3, it was found that under different cutoff voltages, at 60°C and a holding voltage of 12 h, all exhibited superior data and better catalytic performance. Relatively speaking, Example 2 had the lowest overpotential and the longest stable operating time (stable operation exceeding 100 h). Analysis shows that with increasing voltage, the degree of battery overcharging increases, and the amount of delithiation increases. Under the same high temperature and holding voltage duration, at 10 mA / cm²... 2 The overpotential at the location is further reduced; in Example 2, it is 10 mA / cm. 2 With an overpotential of only 334 mV, it exhibited the best alkaline water electrolysis oxygen evolution catalytic performance. However, with further increases in the cutoff voltage, the catalytic performance did not improve further when the overcharge voltage in Example 3 reached 4.8 V. This was because the excessively high overcharge voltage led to excessive lithium removal, resulting in irreversible collapse of the formed structure, making the structure more unstable and hindering the catalytic process.

[0078] Based on these results, Example 4 and Comparative Example 3 were prepared with different holding times to target the optimal performance of Example 2. A comparison of their performance in Table 1 shows that both short and long holding times reduce catalytic efficiency and stability. This indicates that holding time is crucial for converting retired lithium cobalt oxide battery cathode materials into highly efficient catalysts. Comparative Example 3, without holding time, exhibits poor overpotential and stability. This is because the vacancies and defects formed in the lithium cobalt oxide battery cathode material after delithiation require high temperature and sustained voltage to increase structural stability, regulate the type of structural defects, and improve catalytic performance. However, Example 4, with a further holding time of 24 h, shows further changes in its internal atomic structure and arrangement. The collapse of some vacancies serving as active centers affects its catalytic activity, and some dislocation defects further distort, causing structural instability. These factors lead to an increase in catalyst overpotential and a decrease in stable operating time.

[0079] Furthermore, Comparative Example 1, serving as a low-temperature comparative example of Example 2, exhibited worse catalytic performance than Example 2, indicating that higher temperatures are required to promote the evolution of its internal structure and the regulation of defects. In summary, the vacancies and defects formed in the lithium cobalt oxide battery cathode material after delithiation require appropriate high temperatures and a holding voltage for a certain period to promote the evolution of its internal structure and regulate defects, thereby improving catalytic performance.

[0080] Table 1. 10 mA / cm² performance of different materials in LSV testing 2 Overpotential and steady-state operation time

[0081] To investigate the structural changes of the treated materials and the mechanism of their enhanced catalytic performance, this invention systematically characterized the materials from macroscopic to microscopic levels. Figure 2 The image shows a photograph of a decommissioned lithium cobalt oxide battery after being processed in step (1) of Example 2 of this invention. As can be seen from the image, a large amount of positive electrode material has detached and adhered to the negative electrode and the separator. This indicates that the high temperature environment and prolonged voltage maintenance led to severe lithium delithiation of the positive electrode. Figure 3 The XRD comparison images of the materials provided in Examples 1-3 and Comparative Example 2 show that the 003 crystal plane of lithium cobalt oxide in Examples 1-3 is shifted to the left compared to Comparative Example 2, indicating that the spacing between the two cobalt-oxygen layers has increased. This is also due to the large-scale removal of the intermediate Li layer. Furthermore, the electrolyte decomposes significantly during the delithiation process, damaging the material structure. It is inferred that a large number of vacancy defects and atomic layer misalignments (dislocation defects) were generated in the lithium cobalt oxide at the cathode. The morphology of the material provided in Example 2 was observed using scanning electron microscopy (SEM), as shown below. Figure 4As shown, the decommissioned lithium cobalt oxide cathode material, after electrochemical and ball milling treatment, exhibits a micron-scale layered structure (average particle size of 2 μm ± 0.2 μm, particle size distribution of 0.5–3 μm), possessing high specific surface area and abundant active sites. Further observation of the atomic arrangement of the material provided in Example 2 using transmission electron microscopy (TEM) reveals... Figure 5 As shown, the electrochemically treated material exhibits significant atomic layer misalignment and bending. The interatomic spacing in these regions changes, and the charge distribution differs from the original material, forming more active sites, which is one of the key reasons for its superior performance. However, prolonged voltage holding further affects its internal structure. Figure 6 As can be seen, the atomic layers in Example 4 are severely misaligned and the structure is locally disordered, which may exacerbate the risk of Co dissolution and structural collapse.

[0082] In summary, under specific treatment, Embodiment 2 of the present invention induces the generation of highly active sites (such as vacancy defects and atomic misalignment) while accelerating the evolution of the defect structure of the material and effectively regulating the stability of the structure. Therefore, the material exhibits the best catalytic performance and has commercial potential.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst based on retired lithium cobalt oxide battery cathode material, characterized in that, Includes the following steps: (a) The retired lithium cobalt oxide battery is charged to the target voltage at a constant current of 0.01 to 0.5 C at a high temperature, and the voltage is maintained at the target voltage for 6 to 24 h under the high temperature condition; The process of maintaining the voltage at the target voltage for 6–24 hours includes: (S1) After the battery voltage reaches the target voltage, stop charging for 5 to 10 seconds, and then charge at a current of 0.01 to 0.5 C to the target voltage; (S2) Repeat step (S1) until the battery maintains the voltage at the target voltage for 6 to 24 hours; (b) Disassemble the retired lithium cobalt oxide battery after step (a), collect the lithium cobalt oxide material in the positive electrode part, grind it to obtain the catalyst; The high temperature is 50–60°C, and the target voltage is 4.2–5 V.

2. The preparation method according to claim 1, characterized in that, The holding voltage of 6–24 h is replaced with a holding voltage of 6–12 h.

3. The preparation method according to claim 1, characterized in that, The nominal voltage of the retired lithium cobalt oxide battery is 3.7 to 3.8 V.

4. The preparation method according to claim 1, characterized in that, The process of collecting the lithium cobalt oxide material from the positive electrode portion includes: immersing the disassembled positive electrode portion in an organic solvent to separate the lithium cobalt oxide material, and then washing and drying the lithium cobalt oxide material.

5. A catalyst based on retired lithium cobalt oxide battery cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. The catalyst according to claim 5, characterized in that, It has at least one of the following characteristics: (1) The catalyst has a micron-scale layered structure; (2) The average particle size of the catalyst is 2 μm ± 0.2 μm.

7. The application of the catalyst according to claim 5 or 6 in the oxygen evolution reaction of water electrolysis.

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