High-curvature nanocluster positive electrode catalyst for lithium oxygen battery and preparation method of high-curvature nanocluster positive electrode catalyst

Abstract

The invention relates to the technical field of lithium-oxygen batteries, in particular to a high-curvature nanocluster positive electrode catalyst for a lithium-oxygen battery and a preparation method of the high-curvature nanocluster positive electrode catalyst. The preparation method comprises the following steps: carrying out deoxidation treatment on a carbon carrier with a twisted structure to obtain a nano carbon sphere carrier; and mixing ruthenium salt, a reducing agent and the carbon nanosphere carrier, and carrying out oxidation-reduction reaction to obtain the high-curvature nanocluster positive electrode catalyst for the lithium-oxygen battery. According to the preparation method, the preparation process is remarkably simplified, the dependence on a high-temperature evaporation source and accurate temperature and evaporation rate control is reduced, and meanwhile tedious steps and strict reaction condition requirements in an atomic layer deposition method are avoided. More importantly, through the method provided by the invention, the limitation of metal loading capacity in a low-dimensional catalyst is successfully broken through, and uniform dispersion of the high-curvature nanoclusters on the carbon nanosphere carrier is realized, so that the catalytic activity is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-oxygen batteries, and particularly to a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries and a preparation method thereof. Background Art

[0002] With the rapid development of the electric vehicle and mobile electronic product industries, the society has put forward higher requirements for secondary batteries. The technical parameters of energy density and power density of lithium-ion batteries based on conventional electrode materials such as lithium iron phosphate, lithium cobaltate cathodes and graphite anodes have approached their limits, and there is an urgent need to develop electrochemical energy storage materials and devices with both high energy density and high safety. Non-aqueous lithium-oxygen batteries have attracted much attention due to their high energy density (the theoretical energy density is about 3500 Wh / kg, which is 3 to 10 times that of traditional lithium-ion batteries) and relatively high output voltage (about 2.96 V), and are considered to be a secondary battery technology with great development potential.

[0003] In recent years, although the performance of lithium-oxygen batteries has made great progress, they still face problems such as low battery energy conversion efficiency, poor rate performance and short cycle life, which severely restrict their large-scale application. As the center of the electrocatalytic reaction, the cathode catalyst of lithium-oxygen batteries is crucial for constructing high-performance lithium-oxygen batteries.

[0004] At present, the reported low-dimensional catalysts, as a new type of catalyst, have shown unique performance advantages in many fields by dispersing metal atoms in the form of single atoms or clusters on the carrier. However, although physical vapor deposition and atomic layer deposition can achieve effective loading of single atoms or clusters, their preparation processes are complex and their repeatability and stability are poor, thus restricting the possibility of their large-scale production. Specifically, physical vapor deposition needs to rely on a high-temperature evaporation source and requires precise control of the temperature and evaporation rate of the evaporation source, and the operation process is quite cumbersome. Atomic layer deposition has a more lengthy process and extremely strict requirements for the sealing performance of the reaction chamber and the control of gas flow. Any minor leakage or flow fluctuation will cause the deposition process to get out of control. In addition, to ensure the dispersed state of single atoms or clusters, the metal loading in low-dimensional catalysts is usually limited to a low level, which directly leads to insufficient catalytic activity. This limitation has greatly hindered the wide application of low-dimensional catalysts in large-scale industrial production. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery and a preparation method thereof. In the present invention, a carbon carrier with a twisted structure is subjected to deoxidation treatment to obtain a nanocarbon sphere carrier. Subsequently, a hydrothermal reduction method is adopted, in which a ruthenium salt, the nanocarbon sphere carrier and a reducing agent are mixed to carry out an oxidation-reduction reaction, so that ruthenium ions are reduced to ruthenium atoms, and the ruthenium atoms aggregate on the nanocarbon sphere carrier to form ruthenium nanoclusters, which are uniformly dispersed on the nanocarbon sphere carrier, thus obtaining the high-curvature nanocluster cathode catalyst for the lithium-oxygen battery. The present invention provides a new preparation method, which overcomes the defects of physical vapor deposition method and atomic layer deposition method. More importantly, through the method of the present invention, the limitation of the metal loading in the low-dimensional catalyst is successfully broken through, and the uniform dispersion of the nanoclusters on the high-curvature nanocarbon sphere carrier is realized, thereby effectively improving the catalytic activity.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The first object of the present invention is to provide a preparation method of a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery, comprising the following steps:

[0008] S1. Subject a carbon carrier with a twisted structure to deoxidation treatment to obtain a nanocarbon sphere carrier.

[0009] S2. Mix a ruthenium salt, a reducing agent and the nanocarbon sphere carrier, and carry out an oxidation-reduction reaction. During the oxidation-reduction reaction, ruthenium ions are reduced to ruthenium atoms, and multiple ruthenium atoms aggregate to form ruthenium nanoclusters. The nanocarbon sphere carrier anchors the ruthenium nanoclusters, so that the ruthenium nanoclusters are uniformly distributed on the nanocarbon sphere carrier, and the reducing agent is oxidized. After drying, a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery is obtained.

[0010] Preferably, the mass ratio of the ruthenium salt to the nanocarbon sphere carrier is 0.1-0.5:50; wherein, when the proportion of the ruthenium salt is lower than 0.1, the catalytic active sites of the high-curvature nanocluster cathode catalyst for the lithium-oxygen battery are insufficient, the stability is poor, and the selectivity is difficult to regulate; when the proportion of the ruthenium salt is higher than 0.5, it leads to an increase in the cost of the high-curvature nanocluster cathode catalyst for the lithium-oxygen battery, the activity is inhibited, the diffusion resistance increases, and the mechanical properties decline.

[0011] Preferably, the conditions of the oxidation-reduction reaction are: reflux at 160°C to 200°C for 1h to 3h.

[0012] Preferably, the conditions for deoxidation treatment are: deoxidation treatment at 1500 °C to 1600 °C for 1 h to 3 h; among them, if the deoxidation time is too short, the oxygen in the carbon support with a twisted structure cannot be sufficiently removed, and a complete nano-carbon sphere support cannot be formed or the performance of the nano-carbon sphere support is poor; while if the time is too long, it will cause overgrowth, aggregation or structural damage of the nano-carbon spheres, affecting their performance as a support. At the same time, during the 1 h to 3 h deoxidation treatment, the surface properties and active sites of the nano-carbon sphere support can be better regulated. If the time is too short, there are insufficient surface active sites; if the time is too long, defects or impurities will be generated on the surface, affecting their interaction with the loaded substances. From the perspective of industrial production, the treatment time of 1 h to 3 h is relatively short, which can improve production efficiency and reduce production costs while ensuring product quality. If the treatment time is too long, it will increase energy consumption and equipment occupancy time, reducing production efficiency. Conducting deoxidation treatment within the time range of 1 h to 3 h has relatively reasonable requirements for equipment and will not cause excessive loss of equipment due to long-term high-temperature and high-pressure conditions, which is conducive to the long-term stable operation and maintenance of the equipment.

[0013] Preferably, the carbon support with a twisted structure is selected from diamond, amino-modified MIL-53(Al), carbon nanocage or onion carbon.

[0014] More preferably, it is diamond. Diamond has the characteristics of simple preparation method, good conductivity and regular tip twisted structure. It can not only increase the interaction between the metal and the nano-carbon sphere support, thereby enhancing the local microenvironment of the metal, but also accelerate the transport of carriers and improve the catalytic activity of the high-curvature nano-cluster cathode catalyst for lithium-oxygen batteries.

[0015] Preferably, amino-modified MIL-53(Al) is prepared according to the following steps:

[0016] Dissolve aluminum chloride hexahydrate and 2-aminoterephthalic acid in water to obtain a mixed solution; then, add urea to the mixed solution and carry out a hydrothermal reaction at 150 °C; among them, the mass ratio of aluminum chloride hexahydrate, 2-aminoterephthalic acid to urea is 1 g to 2 g: 1 g to 1.5 g: 0 to 1.5 g; the morphology of the MOF, such as blocky, flaky or sea urchin-like, is adjusted by the amount of urea used.

[0017] Preferably, onion carbon is prepared according to the following steps:

[0018] Mix m-aminophenol, water, absolute ethanol and ammonia water, then add formaldehyde solution and acetone. After standing, centrifuging and washing, perform freeze-drying to obtain single-shell hollow porous nanospheres; in an argon atmosphere, react the single-shell hollow porous nanospheres in a tubular furnace at 800 °C for 6 h. To obtain multi-layer hollow carbon nanospheres, remix the single-shell hollow porous nanospheres with m-aminophenol, water, absolute ethanol and ammonia water, and repeat the above steps to obtain multi-layer hollow carbon nanospheres. Among them, the mass-volume ratio of m-aminophenol, water, absolute ethanol to ammonia water is 0.2 g - 0.5 g: 40 mL - 60 mL: 20 mL - 30 mL: 0.2 mL - 1 mL; the mass-volume ratio of m-aminophenol to formaldehyde solution is 0.2 g - 0.5 g: 0.2 mL - 0.5 mL.

[0019] Preferably, the ruthenium salt is selected from ruthenium chloride hydrate, ruthenium acetylacetonate, ruthenium acetate, ruthenium nitrate or ruthenium sulfate.

[0020] Preferably, the reducing agent is selected from polyol solutions or organic amine solutions.

[0021] Preferably, the polyol solution is selected from ethylene glycol or glycerol.

[0022] Preferably, the organic amine solution is selected from ethylenediamine or triethylamine.

[0023] Preferably, dry at 80 °C - 120 °C until the water content is lower than 20 ppm to avoid the influence of water on the battery system.

[0024] The second object of the present invention is to provide a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries prepared by the above preparation method.

[0025] Preferably, the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries is in the shape of multi-layer carbon nanospheres.

[0026] The third object of the present invention is to provide a high-curvature nanocluster cathode electrode for lithium-oxygen batteries, which is composed of the above high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, a binder, a solvent and a current collector. After mixing the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, the binder and the solvent, a slurry is obtained, and then the slurry is coated on both sides of the current collector and dried to obtain.

[0027] Preferably, the mass ratio of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries to the binder is 4 - 6: 1 - 2.

[0028] Preferably, the binder is selected from polyvinylidene fluoride or naphthol.

[0029] Preferably, the solvent is selected from ethanol, N-methylpyrrolidone or N,N-dimethylformamide.

[0030] Preferably, the current collector is selected from carbon paper, carbon cloth or nickel foam.

[0031] The fourth object of the present invention is to provide a lithium-oxygen battery, which is made of the above-mentioned high-curvature nanocluster cathode material, separator, anode material and electrolyte.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The present invention provides a preparation method of a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery. The carbon carrier with a twisted structure is subjected to deoxidation treatment to obtain a nanocarbon sphere carrier; a ruthenium salt, a reducing agent and the nanocarbon sphere carrier are mixed to carry out an oxidation-reduction reaction. During the oxidation-reduction reaction, ruthenium ions are reduced to ruthenium atoms, and multiple ruthenium atoms aggregate to form ruthenium nanoclusters. The nanocarbon sphere carrier anchors the ruthenium nanoclusters, so that the ruthenium nanoclusters are uniformly distributed on the nanocarbon sphere carrier, and a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery is obtained. The preparation method of the present invention not only significantly simplifies the preparation process, reduces the dependence on high-temperature evaporation sources and precise temperature and evaporation rate control, but also avoids the cumbersome steps and strict reaction condition requirements in the atomic layer deposition method. More importantly, through the method of the present invention, the limitation of the metal loading in the low-dimensional catalyst is successfully broken through, and the uniform dispersion of the high-curvature nanoclusters on the nanocarbon sphere carrier is realized, thereby effectively improving the catalytic activity.

[0034] 2. The present invention applies geometric constraints to the loaded ruthenium through a carbon carrier with a twisted structure, effectively restricting the migration and aggregation of ruthenium nanoclusters and ensuring that ruthenium atoms maintain a highly dispersed state. In addition, there are metal-support interactions and tip effects between the atoms inside the ruthenium nanoclusters and between the ruthenium nanoclusters and the nanocarbon sphere carrier. This electronic-level interaction can precisely adjust the electronic structure of ruthenium atoms, and thus significantly improve the utilization efficiency of the catalytic active sites of the high-curvature nanocluster cathode catalyst for a lithium-oxygen battery.

[0035] Among them, the carbon carrier with a twisted structure can change the local electric field intensity of the ruthenium nanoclusters, thereby improving the carrier transport and enhancing the catalytic activity of the high-curvature nanocluster cathode catalyst for a lithium-oxygen battery.

[0036] 3. The high-curvature nanocluster cathode catalyst for lithium-oxygen batteries provided by the present invention has high catalytic activity, strong selectivity and good stability. It is mainly attributed to: First, the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries of the present invention is in the form of multilayer carbon nanospheres. There are many tip parts in this structure, and the atomic arrangement at these tips is special, forming a large number of unsaturated bonds and dangling bonds, which provide rich active sites for the catalytic reaction of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, thereby significantly enhancing the catalytic activity; second, the tip effect increases the charge density at the tip of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, which is beneficial to the transmission and transfer of electrons. In the electrocatalytic reaction, this increase in charge density accelerates the electron transfer rate between the reactant and the catalyst, optimizes the reaction kinetics, and further improves the catalytic activity; third, the tip of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries can generate a highly localized electric field, which affects the adsorption and reaction orientation of the reactant molecules, guides the reaction in a specific direction, and thus improves the selectivity of the target product; fourth, when preparing high-curvature nanocluster cathode catalysts for lithium-oxygen batteries, the tip effect helps to evenly disperse the ruthenium nanoclusters on the surface of the nanocarbon ball carrier. Since ruthenium nanoclusters are not easy to agglomerate, the reduction in the number of active sites caused by agglomeration is avoided, thereby significantly enhancing the stability and durability of the catalyst; fifth, the multilayer spherical structure of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries is inherently stable, and the tip effect enables the carbon balls to better maintain their structural integrity through charge distribution and stress regulation mechanisms when subjected to physical and chemical effects under reaction conditions.

[0037] 4. The present invention also applies high-curvature nanocluster cathode materials to lithium-oxygen batteries. 2 The current density is 0.12 mAh / cm 2 The battery exhibited a discharge voltage of 2.77V and a charge voltage of 3.54V at a limited capacity of 100mA / g, with an energy conversion efficiency of 78.2%. In addition, the invented lithium-oxygen battery can be stably cycled for more than 300h under low polarization conditions at a current density of 100mA / g and a limited specific capacity of 1000mAh / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 X-ray photoelectron spectra of the Ru NCs / CS catalyst prepared in Example 1 and the Ru NPs / rG prepared in Comparative Example 1, wherein a is Example 1 and b is Comparative Example 1.

[0039] Figure 2TEM images of the Ru NCs / CS catalyst prepared in Example 1 and the Ru NPs / rG prepared in Comparative Example 1, where a is Example 1 and b is Comparative Example 1.

[0040] Figure 3 Raman spectra of the Ru NCs / CS catalyst prepared in Example 1 and the Ru NPs / rG prepared in Comparative Example 1, where a is Example 1 and b is Comparative Example 1.

[0041] Figure 4 Initial charge-discharge curves of the lithium-oxygen batteries assembled with Example 1 and Comparative Example 1, where a is Example 1 and b is Comparative Example 1.

[0042] Figure 5 Charge-discharge cycling curves of the lithium-oxygen batteries assembled with Example 1 and Comparative Example 1, where a is Example 1 and b is Comparative Example 1.

[0043] Figure 6 SEM images of the positive electrodes after discharge of the lithium-oxygen batteries assembled with Example 1 and Comparative Example 1, where a is Example 1 and b is Comparative Example 1. Detailed implementation manners

[0044] The technical solutions of the present invention will be clearly and completely described below in combination with the data in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0045] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0046] In the prior art, although low-dimensional catalysts have shown potential in the catalytic aspect of the positive electrode of lithium-oxygen batteries, their preparation process is complex, the requirements for equipment are high, and the metal loading is limited, resulting in insufficient catalytic activity. Specifically, traditional physical vapor deposition and atomic layer deposition methods not only require precise control of the temperature and evaporation rate of the high-temperature evaporation source, as well as the sealing performance and gas flow of the reaction chamber, but also have problems such as cumbersome preparation processes, poor repeatability and stability. These factors limit the large-scale production and application of low-dimensional catalysts. In addition, since the dispersion state of metal atoms or clusters on the carrier needs to be strictly controlled, the metal loading in low-dimensional catalysts is usually low, which further limits the improvement of their catalytic activity.

[0047] In view of the defects existing in the above-mentioned prior art, the present invention provides a preparation method of a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery, which comprises the following steps: performing deoxidation treatment on a carbon support with a twisted structure to obtain a nanocarbon sphere support; mixing a ruthenium salt, a reducing agent and the nanocarbon sphere support, and performing an oxidation-reduction reaction. During the oxidation-reduction reaction, ruthenium ions are reduced to ruthenium atoms, and multiple ruthenium atoms aggregate to form ruthenium nanoclusters. The nanocarbon sphere support anchors the ruthenium nanoclusters, so that the ruthenium nanoclusters are uniformly distributed on the nanocarbon sphere support, and a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery is obtained.

[0048] By adopting a carbon support with a twisted structure and performing deoxidation treatment, the present invention solves the problems of uneven dispersion and easy aggregation of metal nanoclusters on the support; by using the hydrothermal reduction method to realize the in-situ reduction and aggregation of ruthenium ions on the nanocarbon sphere support, high-curvature nanoclusters are formed and their uniform dispersion on the support is realized, thereby effectively improving the catalytic activity. The preparation method of the present invention is simple, and overcomes the problems of complex preparation process, high equipment requirements and limited metal loading in the preparation of traditional low-dimensional catalysts.

[0049] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0050] Example 1

[0051] A preparation method of a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery comprises the following steps:

[0052] S1. Deoxidize diamond in an argon atmosphere at 1500 °C for 1.5 h to obtain a nanocarbon sphere support.

[0053] S2. After mixing and dissolving 0.2 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, add 50 mg of the nanocarbon sphere support, and ultrasonically mix evenly to obtain a mixture.

[0054] S3. Reflux the mixture at 170 °C for 3 h, cool it to room temperature, then centrifuge it at 8000 rad / min for 10 min, remove the supernatant to obtain a solid product; subsequently, repeatedly centrifuge and wash the solid product with deionized water and ethanol, and then place the solid product in a vacuum drying oven and dry it at 80 °C for 12 h to obtain a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery, denoted as Ru NCs / CS.

[0055] Example 2

[0056] A preparation method of a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery comprises the following steps:

[0057] S1. Deoxygenate diamond in an argon atmosphere at 1600 °C for 1.5 h to obtain a nanocarbon sphere support.

[0058] S2. Mix and dissolve 0.1 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, then add 50 mg of the nanocarbon sphere support and ultrasonically mix evenly to obtain a mixture.

[0059] S3. Reflux the mixture at 200 °C for 3 h. After cooling to room temperature, centrifuge at 8000 rad / min for 10 min to remove the supernatant and obtain a solid product. Subsequently, repeatedly centrifuge and wash the solid product with deionized water and ethanol, then place the solid product in a vacuum drying oven and dry at 80 °C for 12 h to obtain a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, denoted as Ru NCs / CS.

[0060] Example 3

[0061] A preparation method of a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, comprising the following steps:

[0062] S1. Deoxygenate diamond in an argon atmosphere at 1500 °C for 1 h to obtain a nanocarbon sphere support.

[0063] S2. Mix and dissolve 0.1 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, then add 25 mg of the nanocarbon sphere support and ultrasonically mix evenly to obtain a mixture.

[0064] S3. Reflux the mixture at 160 °C for 1 h. After cooling to room temperature, centrifuge at 8000 rad / min for 10 min to remove the supernatant and obtain a solid product. Subsequently, repeatedly centrifuge and wash the solid product with deionized water and ethanol, then place the solid product in a vacuum drying oven and dry at 80 °C for 24 h to obtain a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, denoted as Ru NCs / CS.

[0065] Example 4

[0066] A preparation method of a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, comprising the following steps:

[0067] S1. Dissolve 1.5 g of aluminum chloride hexahydrate and 1.1 g of 2-aminoterephthalic acid in water to obtain a mixed solution; subsequently, add 1.08 g of urea to the mixed solution and react at 150 °C for 5 h to obtain amino-modified MIL-53(Al).

[0068] S2. Deoxygenate the amino-modified MIL-53(Al) in an argon atmosphere at 1500 °C for 3 h to obtain a nanocarbon sphere support.

[0069] S3. After mixing and dissolving 0.2 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, 50 mg of the nanocarbon sphere support is added, and the mixture is ultrasonically mixed evenly to obtain a mixture; wherein, the mass ratio of ruthenium chloride hydrate to the nanocarbon sphere support is 1:250.

[0070] S4. The mixture is refluxed at 200 °C for 1 h. After cooling to room temperature, it is centrifuged at 8000 rad / min for 10 min, and the supernatant is removed to obtain a solid product; Subsequently, the solid product is centrifuged and washed multiple times with deionized water and ethanol, and then the solid product is placed in a vacuum drying oven and dried at 80 °C for 12 h to obtain a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, denoted as Ru NCs / CS.

[0071] Example 5

[0072] A preparation method of a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries includes the following steps:

[0073] S1. Mix 0.2 g of m-aminophenol, 40 mL of ultrapure water, 20 mL of absolute ethanol, and 0.2 mL of ammonia water, then add 0.2 mL of formaldehyde solution, stir for 30 min, then add 40 mL of acetone, let it stand for 3 h, centrifuge and wash three times, and freeze-dry at -20 °C for 5 h to obtain single-shell hollow porous nanospheres; In an argon atmosphere, the single-shell hollow porous nanospheres are reacted in a tubular furnace at 800 °C for 6 h to obtain single-shell hollow porous carbon nanospheres. The single-shell hollow porous carbon nanospheres are mixed again with 0.2 g of m-aminophenol, 40 mL of water, 20 mL of absolute ethanol, and 0.2 mL of ammonia water, then add 0.2 mL of formaldehyde solution, stir for 30 min, then add 40 mL of acetone, let it stand for 3 h, centrifuge and wash three times, and freeze-dry at -20 °C for 5 h to obtain double-shell hollow porous nanospheres; Repeat the above steps 5 times to obtain five-layer hollow carbon nanospheres, namely onion carbon.

[0074] S2. Deoxygenate the onion carbon in an argon atmosphere at 1500 °C for 3 h to obtain a nanocarbon sphere support.

[0075] S3. After mixing and dissolving 0.2 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, 50 mg of the nanocarbon sphere support is added, and the mixture is ultrasonically mixed evenly to obtain a mixture; wherein, the mass ratio of ruthenium chloride hydrate to the nanocarbon sphere support is 1:250.

[0076] S4. Reflux the mixture at 200 °C for 1 h. After cooling to room temperature, centrifuge at 8000 rad / min for 10 min, remove the supernatant to obtain a solid product. Subsequently, wash the solid product by centrifugation with deionized water and ethanol multiple times, and then place the solid product in a vacuum drying oven and dry it at 80 °C for 12 h to obtain a high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, denoted as Ru NCs / CS.

[0077] Comparative Example 1

[0078] A preparation method of nanoparticles-two-dimensional reduced graphene includes the following steps:

[0079] S1. Under an argon atmosphere, reduce graphene oxide at 1050 °C for 20 min to obtain two-dimensional reduced graphene.

[0080] S2. After mixing and dissolving 0.2 mg of ruthenium chloride hydrate and 111 g of ethylene glycol solution, add 50 mg of two-dimensional reduced graphene and mix evenly by ultrasonic treatment to obtain a mixture. Among them, the mass ratio of ruthenium chloride hydrate to two-dimensional reduced graphene is 1:250.

[0081] S3. Reflux the mixture at 170 °C for 3 h, cool to room temperature, centrifuge at 8000 rad / min for 10 min, remove the supernatant to obtain a solid product. Subsequently, wash the solid product by centrifugation with deionized water and ethanol multiple times, and then place the solid product in a vacuum drying oven and dry it at 80 °C for 12 h to obtain nanoparticles-two-dimensional reduced graphene, denoted as Ru NPs / rG.

[0082] a. Surface chemical composition characterization

[0083] Observation Figure 1 From the a graph in 1 / 2 it can be seen that the spin-orbit splitting doublet peaks of Ru 3p 3 / 2 indicate the successful loading of Ru 0 onto the nanocarbon sphere support in Ru NCs / CS prepared in Example 1 of the present invention. From the b graph in Figure 1 it can be seen that Ru 0 is successfully loaded onto the two-dimensional reduced graphene nanosheet support, and the binding energy of Ru 3p 3 / 2 varies with different nanocarbon sphere supports.

[0084] From Figure 2As can be seen from Figure a in [reference], the particle size of Ru nanoclusters in Ru NCs / CS prepared in Example 1 of the present invention is about 1 nm to 2 nm, endowing it with the advantages of high activity, high selectivity, and high stability. First, Ru nanoclusters have a large specific surface area, and a large number of atoms are exposed on the surface, thus providing abundant active sites. These active sites can fully contact and interact with reactants, thereby greatly enhancing the rate of catalytic reactions. Second, small-sized nanoclusters can precisely regulate the adsorption process of oxygen and reaction intermediates in lithium-oxygen batteries. This property helps to regulate the growth path of lithium peroxide, thereby optimizing the electrochemical performance of the battery. Finally, there is a strong interaction between the carbon nanosphere carrier and Ru nanoclusters, which significantly enhances the stability of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries, making it not prone to agglomeration, sintering, or loss during the catalytic reaction. Even after multiple cycles of use, it can still maintain high catalytic activity and selectivity. This property not only extends the service life of the high-curvature nanocluster cathode catalyst for lithium-oxygen batteries but also effectively reduces the usage cost. From Figure 2 As can be seen from Figure b in [reference], the particle size of Ru nanoparticles in Ru NPs / rG prepared in Comparative Example 1 is about 3 nm to 5 nm.

[0085] b. Defect site characterization

[0086] From Figure 3 As can be seen from Figure a in [reference], Ru NCs / CS prepared in Example 1 of the present invention has more defects and exhibits more excellent electrocatalytic activity. From Figure 3 As can be seen from Figure b in [reference], Ru NPs / rG prepared in Comparative Example 1 has fewer defects and relatively lower electrocatalytic activity.

[0087] c. The Ru loadings in Ru NCs / CS prepared in Example 1 and Ru NPs / rG prepared in Comparative Example 1 were analyzed, and the results are shown in Table 1.

[0088] Table 1 ICP results of Ru NCs / CS prepared in Example 1 and Ru NPs / rG prepared in Comparative Example 1

[0089] sample Ru2402 Ru2661 Ru2678 average Example 1 0.7604％ 0.9600％ 0.6462％ 0.7889％ Comparative Example 1 0.3909％ 0.5009％ 0.3276％ 0.4065％

[0090] As can be seen from Table 1, in Ru NCs / CS prepared in Example 1 of the present invention, the content of Ru nanoclusters is 0.7889%, indicating that Ru NCs / CS prepared by the preparation method of the present invention has a low content of noble metals while maintaining high catalytic activity, which is beneficial to reducing the cost of the catalyst. In contrast, the content of Ru nanoparticles in Ru NPs / rG prepared in Comparative Example 1 is 0.4065%, with a high noble metal content and low catalytic activity, indicating that the low-curvature carrier reduces the utilization rate of the catalyst, resulting in an increase in the catalyst cost.

[0091] d. Application method:

[0092] Disperse the RuNCs / CS prepared in Example 1 and the RuNPs / rG prepared in Comparative Example 1 into ethanol at a mass ratio of 4:1 with the binder polyvinylidene fluoride, crush them, and then evenly spray them on both sides of the hydrophilic carbon paper. After drying, a high-curvature nanocluster cathode material and a nanoparticle-reduced graphene oxide cathode material are obtained respectively.

[0093] Take the high-curvature nanocluster cathode material and the nanoparticle-reduced graphene oxide cathode material as the cathode, metallic lithium as the anode, and a glass fiber separator with 1 mol / L LiTFSI / TEGDME liquid electrolyte. In a vacuum glove box, use the metallic lithium anode as the lower shell, place the glass fiber separator and the cathode on it in sequence, and finally drop 100 μL of the electrolyte to fully wet the cathode and the glass fiber separator. Cover the upper shell of the button cell and use a tablet press to tightly seal the cell to obtain a lithium-oxygen battery, denoted as Ru NCs / CS-lithium-oxygen battery and RuNPs / rG-lithium-oxygen battery respectively.

[0094] Test the charge-discharge performance of the lithium-oxygen battery. The test conditions are: current density 0.04 mA / cm 2 , and the cut-off voltage is 2 V to 4.5 V.

[0095] As shown in Figure 4 Figure a, the RuNCs / CS-lithium-oxygen battery exhibits a discharge voltage of 2.77 V and a charge voltage of 3.54 V at a current density of 0.04 mA / cm 2 and a limited capacity of 0.12 mAh / cm 2 , with an energy conversion efficiency as high as 78.2%. As shown in Figure 4 Figure b, the Ru NPs / rG-lithium-oxygen battery exhibits a discharge voltage of 2.48 V and a charge voltage of 3.68 V at a current density of 0.04 mA / cm 2 and a limited capacity of 0.12 mAh / cm 2 , with an energy conversion efficiency reaching 67.4%.

[0096] As shown in Figure 5 Figure a, the RuNCs / CS-lithium-oxygen battery can stably cycle for more than 300 h at a low polarization voltage at a current density of 100 mA / g and a limited specific capacity of 1000 mAh / g. As shown in Figure 5 Figure b, the RuNPs / rG-lithium-oxygen battery exceeds 4.0 V in voltage after only a few cycles at a current density of 100 mA / g and a limited specific capacity of 1000 mAh / g.

[0097] e. Characterization of the growth behavior of the discharge products of lithium-oxygen batteries

[0098] As can be seen from Figure a in Figure 6 , the RuNCs / CS-lithium-oxygen battery produces triangular prism-shaped discharge products, which are induced by the local electric field effect, prompting the discharge products to undergo a "bottom-up" growth process. This process can not only significantly improve the utilization efficiency of reactive sites but also effectively optimize the lithium-ion transport path, further enhancing the battery's discharge capacity and extending its cycle life. As can be seen from Figure b in Figure 6 , the RuNPs / rG-lithium-oxygen battery produces ring-shaped discharge products aggregated on the surface with a lower curvature, showing a surface growth mode.

[0099] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, to avoid redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery, characterized in that: The steps include: Deoxidizing the carbon carrier with a twisted structure to obtain a nano carbon ball carrier; A ruthenium salt, a reducing agent and a nano-carbon ball carrier are mixed and subjected to a redox reaction. During the redox reaction, ruthenium ions are reduced to ruthenium atoms. Multiple ruthenium atoms aggregate to form ruthenium nanoclusters. The nano-carbon ball carrier anchors the ruthenium nanoclusters so that the ruthenium nanoclusters are evenly distributed on the nano-carbon ball carrier. The reducing agent is oxidized to obtain a high-curvature nanocluster positive electrode catalyst for a lithium-oxygen battery.

2. The method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery according to claim 1, characterized in that: The carbon support with a twisted structure is selected from diamond, amino-modified MIL-53(Al), onion carbon or carbon nanocage.

3. The method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery according to claim 1, characterized in that: The mass ratio of ruthenium salt to nano carbon ball carrier is 0.1-0.5:25-50.

4. The method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery according to claim 1, characterized in that: The conditions for the deoxidation treatment are: deoxidation treatment at 1500°C to 1600°C for 1h to 3h.

5. The method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery according to claim 1, characterized in that: The conditions for the redox reaction are: reflux at 160°C to 200°C for 1h to 3h.

6. The method for preparing a high-curvature nanocluster cathode catalyst for a lithium-oxygen battery according to claim 1, characterized in that: The reducing agent is selected from a polyol solution or an organic amine solution.

7. A high-curvature nanocluster cathode catalyst for a lithium-oxygen battery prepared by the preparation method according to any one of claims 1 to 6.

8. The high-curvature nanocluster cathode catalyst for lithium-oxygen batteries according to claim 7, characterized in that: The high-curvature nanocluster cathode catalyst for lithium-oxygen batteries is in the form of multilayered carbon nanospheres.

9. A high-curvature nanocluster positive electrode for a lithium-oxygen battery, characterized in that: The high-curvature nanocluster positive electrode sheet for a lithium-oxygen battery is composed of the high-curvature nanocluster positive electrode catalyst for a lithium-oxygen battery according to claim 7, a binder, a solvent and a current collector. The high-curvature nanocluster positive electrode catalyst for a lithium-oxygen battery, the binder and the solvent are mixed to obtain a slurry, which is then coated on both sides of the current collector and dried to obtain the obtained product.

10. A lithium-oxygen battery, characterized in that: The lithium-oxygen battery is made of the high-curvature nanocluster positive electrode sheet for the lithium-oxygen battery according to claim 9, a separator, a negative electrode sheet and an electrolyte.

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