Preparation method and application of positive electrode catalyst of lithium-oxygen battery

Abstract

The application belongs to the technical field of lithium-oxygen battery materials, and particularly relates to a preparation method and application of a positive electrode catalyst of a lithium-oxygen battery. The method comprises the following steps: S1: dissolving iron salt, cobalt salt and sodium hydroxide in a first solvent, then adding ethylenediamine to obtain a mixed solution, and performing a reaction at a temperature of 105-115 DEG C to obtain a cobalt-iron ferrite carrier; S2: then, the cobalt-iron ferrite carrier obtained in S1 is heat-treated at 145-155 DEG C under 5% argon-hydrogen mixed gas to introduce oxygen defects, and the obtained material is dispersed in a second solvent; S3: a certain amount of palladium precursor solution is added, a reducing agent is added after stirring for a certain time to obtain a palladium nanoparticle loaded material, and then the material is annealed at 340-360 DEG C under argon protection to obtain the positive electrode catalyst. The application solves the slow oxygen reduction / precipitation kinetics in the lithium-oxygen battery, effectively solves the core problem in the existing lithium-oxygen battery technology, and thus promotes the commercialization process.

Description

Technical Field

[0001] This invention relates to the field of lithium-oxygen battery materials technology, specifically to a method for preparing and applying a positive electrode catalyst for lithium-oxygen batteries. Background Technology

[0002] Against the backdrop of surging global energy demand and the dual pressures of depleted traditional fossil fuels and environmental pollution, the development of advanced energy storage and conversion systems with ultra-high energy density, low cost, and environmental friendliness has become a frontier of international scientific research. Lithium-oxygen batteries, as outstanding representatives of next-generation metal-air battery systems, boast a theoretical energy density as high as 3500 Wh / kg. −1 (Based on the reversible reaction 2Li+O2→Li2O2), it is comparable to gasoline in terms of energy efficiency and is widely recognized as the ultimate energy storage solution that can completely solve the "range anxiety" of electric vehicles and is widely used in high-end fields such as aerospace and deep-sea exploration.

[0003] However, despite its extremely promising prospects, the commercialization of lithium-oxygen batteries is hampered by a series of deep-seated scientific and technological challenges. The most critical bottleneck lies in the extremely sluggish electrochemical kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the cathode. This not only results in a huge potential difference between the discharge and charging voltages (i.e., excessively high overpotential), severely reducing the battery's energy conversion efficiency, but also triggers side reactions at high potentials. Simultaneously, lithium peroxide (Li2O2), a discharge product insoluble in organic electrolytes and possessing electrical insulating properties, easily forms a passivation layer on the porous cathode surface during discharge, leading to pore blockage. This not only limits the utilization rate of the battery's active sites but also drastically deteriorates the battery's rate performance and cycle stability at high current densities. Furthermore, discharge intermediates (such as superoxide radicals) possess extremely strong oxidizing activity, inevitably attacking organic electrolytes and carbon-based electrode materials, triggering severe decomposition side reactions and generating irreversible products such as lithium carbonate (Li2CO3), resulting in a significant reduction in cycle life. To overcome these technological barriers, electrocatalysts play a crucial role in regulating the morphology of discharge products, lowering reaction energy barriers, and suppressing side reactions. Although noble metals such as platinum (Pt), ruthenium (Ru), and iridium (Ir) and their oxides exhibit excellent catalytic activity, their scarcity leading to high costs and poor long-term stability under high current severely hinders the large-scale commercialization of lithium-oxygen batteries. Therefore, developing catalysts with high catalytic activity, low noble metal loading, and high stability for lithium-oxygen batteries is a pressing challenge in this field. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0006] A method for preparing a positive electrode catalyst for a lithium-oxygen battery includes the following steps:

[0007] S1: Iron salt, cobalt salt and sodium hydroxide are dissolved in the first solvent, followed by the addition of ethylenediamine to obtain a mixed solution. The reaction is carried out at a temperature of 105-115℃ to obtain a cobalt-iron ferrite support.

[0008] S2: Subsequently, the cobalt-iron ferrite support obtained in S1 was heat-treated at 145-155℃ under a 5% argon-hydrogen mixture to introduce oxygen defects, and the resulting material was dispersed in a second solvent.

[0009] S3: Add a certain amount of palladium precursor solution, stir for a certain time, add a reducing agent to obtain palladium nanoparticle-supported material, and then anneal under argon protection at 340-360℃ to obtain positive electrode catalyst.

[0010] In a preferred embodiment of the method for preparing the positive electrode catalyst of a lithium-oxygen battery according to the present invention, both the first solvent and the second solvent are deionized water.

[0011] In a preferred embodiment of the preparation method of the positive electrode catalyst of the lithium-oxygen battery according to the present invention, the molar ratio of iron salt, cobalt salt and sodium hydroxide in S1 is (2-4):(1-2):(16-20).

[0012] In a preferred embodiment of the method for preparing a positive electrode catalyst for a lithium-oxygen battery according to the present invention, the iron salt is ferric chloride hexahydrate; the cobalt salt is cobalt chloride hexahydrate; and the molar volume ratio of the iron salt to the first solvent is (2-4) mol: 7 mL.

[0013] In a preferred embodiment of the preparation method of the positive electrode catalyst for a lithium-oxygen battery according to the present invention, the volume ratio of ethylenediamine to the first solvent in S1 is (1-2):1, and the heat treatment time is 15 h.

[0014] In a preferred embodiment of the preparation method of the positive electrode catalyst for a lithium-oxygen battery according to the present invention, the heat treatment time in step S2 is 30 min, and the ratio of the material to the second solvent is 100 mg: 20 mL.

[0015] In a preferred embodiment of the method for preparing the positive electrode catalyst of a lithium-oxygen battery according to the present invention, the concentration of the palladium precursor solution in step S3 is 2-4 mg / mL. -1 The volume of the palladium precursor solution is 5 mL; the stirring time is 10 h; and the concentration of the reducing agent is 5.5 mg / mL. -1 The volume of the reducing agent is 3 mL; the annealing time is 2 h.

[0016] A method for preparing a positive electrode catalyst for a lithium-oxygen battery, and the application of the resulting positive electrode catalyst in the preparation of metal gas batteries.

[0017] As a preferred embodiment of the application of the positive electrode catalyst of the lithium-oxygen battery described in this invention, the battery is a lithium-oxygen battery, which includes a negative electrode, an electrolyte, and a positive electrode catalyst.

[0018] In a preferred embodiment of the application of the positive electrode catalyst of the lithium-oxygen battery described in this invention, the electrolyte is lithium bis(trifluoromethanesulfonylimide) dissolved in tetraethylene glycol dimethyl ether; and the positive electrode catalyst is coated on carbon cloth.

[0019] Compared with existing technologies, the advantages of this invention are as follows: By loading Pd nanoparticles onto a ferrimagnetic defect cobalt-iron ferrite, the Pd nanoparticles are uniformly loaded on the magnetic support, effectively preventing particle aggregation and maximizing the exposure of active sites. Furthermore, the metal-support interaction between the Pd nanoparticles and the magnetic support optimizes the electronic structure of Pd and induces its magnetism, thereby optimizing the spin-dependent reaction kinetics of ORR / OER. Applying this cathode catalyst to lithium-oxygen batteries can address the problem of insufficient activity in traditional cathode catalysts, solve the slow oxygen reduction / evolution kinetics in lithium-oxygen batteries, effectively solve the core problems in existing lithium-oxygen battery technology, and thus promote its commercialization. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0021] Figure 1 The XRD patterns of Pd / CFO prepared in Example 1, Pd / C prepared in Comparative Example 1, CFO prepared in Comparative Example 2, and Pd / CFO prepared in Comparative Example 3 are defect-free.

[0022] Figure 2 These are HRTEM images obtained in the examples of the present invention, wherein (a) is the HRTEM image of Pd / C obtained in Comparative Example 1, and (b) is the HRTEM image of CFO obtained in Comparative Example 2.

[0023] Figure 3 The image shows a HAADF-STEM image of Pd / CFO obtained in Example 1 of this invention, with the inset showing particle size statistics.

[0024] Figure 4 The image shown is an HRTEM image of Pd / CFO obtained in Embodiment 1 of the present invention.

[0025] Figure 5 X-ray magnetic circular dichroism spectroscopy of the Pd M-side of Pd / CFO prepared in Example 1 of this invention;

[0026] Figure 6 The graphs show the performance of Pd / CFO prepared in Examples 1, 2 and 3 of this invention, Pd / C prepared in Comparative Example 1, CFO prepared in Comparative Example 2 and Pd / CFO prepared in Comparative Example 3 as defect-free positive electrode catalysts for lithium-oxygen batteries. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] In one embodiment of the present invention, a method for preparing a positive electrode catalyst for a lithium-oxygen battery is provided, comprising the following steps:

[0031] S1. Dissolve 2-4 mmol of iron salt, 1-2 mmol of cobalt salt and 16-20 mmol of sodium hydroxide in 7 mL of the first solvent, and then add 7-14 mL of ethylenediamine to obtain a mixed solution.

[0032] S2. The above mixed solution is reacted at a temperature of 105-115℃ to obtain a cobalt-iron ferrite (CFO) support.

[0033] S3. The obtained ferrite support is treated at 145-155℃ for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects.

[0034] S4. Disperse the obtained material in the second solvent, add a certain amount of palladium precursor solution, and stir for a certain period of time;

[0035] S5. Adding a reducing agent yields a material supported on palladium nanoparticles;

[0036] S6. Argon protection annealing at 340-360℃ yields the positive electrode catalyst (Pd / CFO).

[0037] It should be noted that both the first and second solvents mentioned above can be deionized water, but are not limited to this.

[0038] In another embodiment of the present invention, a lithium-oxygen battery is also provided, comprising a negative electrode, an electrolyte, and the above-described positive electrode catalyst.

[0039] Specifically, CR2025 button cells can be used, whose positive electrode casing has holes. Lithium-oxygen batteries mainly consist of the following key components:

[0040] 1. Negative electrode: Lithium sheet; Pure lithium sheet is used as the negative electrode material. Lithium as the negative electrode has extremely high theoretical specific capacity (3860 mAh / g) and the lowest electrode potential (−3.04 V vs RHE); During discharge, the lithium sheet undergoes an oxidation reaction and releases electrons.

[0041] 2. Electrolyte: Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in tetraethylene glycol dimethyl ether (TEGDME) solution, wherein the concentration of LiTFSI is 1 mol / L; this electrolyte has high ionic conductivity, wide electrochemical window and good stability.

[0042] 3. Carbon cloth coated with positive electrode catalyst (Pd / CFO): Pd / CFO, Super P, and PVDF are added to NMP in a ratio of 8:1:1 to prepare a slurry. The slurry is loaded onto the carbon cloth by ultrasonic spraying and then dried at 80°C to obtain the positive electrode.

[0043] The lithium-oxygen battery provided in this invention operates based on the highly efficient catalytic effect of the positive electrode catalyst Pd / CFO in a specific electrochemical reaction.

[0044] When a lithium-oxygen battery is working, the discharge process is as follows: the lithium anode undergoes an oxidation reaction (Li→Li). + +e −Simultaneously, under the action of the positive electrode catalyst Pd / CFO, oxygen in the air undergoes ORR (Organic Oxygen Regeneration), consuming electrons and combining with ions in the electrolyte. The high ORR activity and stability of the positive electrode catalyst Pd / CFO ensure efficient energy output and long cycle life. The charging process is as follows: under the action of an external power source, the reaction proceeds in reverse, the positive electrode catalyst Pd / CFO promotes OER and regenerates oxygen, while a reduction reaction occurs at the lithium negative electrode.

[0045] The embodiments of this invention provide a high-performance, multifunctional cathode catalyst for lithium-oxygen batteries through the detailed technical solutions described above, offering an innovative approach to addressing key challenges in current energy storage and lithium-oxygen battery fields. These embodiments overcome the shortcomings of existing lithium-oxygen battery technologies by introducing Pd / CFO as the cathode catalyst, achieving the following objectives:

[0046] 1. Significantly improves the performance of lithium-oxygen batteries. Solves the problems of slow ORR / OER kinetics and poor cathode stability.

[0047] 2. Achieving cost-effectiveness and sustainability. Pd has a relatively low load, thus promoting the commercialization and sustainable development of lithium-oxygen battery technology.

[0048] The following embodiments are some specific implementation examples of the present invention in practical applications, but are not limited thereto.

[0049] Example 1: This example provides a method for preparing a positive electrode catalyst for a lithium-oxygen battery, including the following steps:

[0050] S1. Dissolve 4 mmol of iron salt, 2 mmol of cobalt salt and 20 mmol of sodium hydroxide in 7 mL of deionized water, stir well at room temperature, and then slowly add 14 mL of ethylenediamine to obtain a mixed solution.

[0051] S2. Stir the above mixed solution continuously for 30 minutes to form a black solution, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 110°C for 15 hours. After cooling to room temperature, centrifuge, wash and vacuum dry the precipitate to obtain the CFO carrier.

[0052] S3. The obtained ferrite support is treated at 150°C for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects.

[0053] S4. Disperse 100 mg of defective CFO carrier in deionized water, and add 5 mL of K2PdCl6 aqueous solution (3 mg / mL). −1 Stir for 10 hours.

[0054] S5. Slowly add 3 mL of NaBH4 aqueous solution (5.5 mg / mL)−1 After stirring for 2 hours, the product was separated using a magnet, washed, and dried.

[0055] S6. The positive electrode catalyst (Pd / CFO) was obtained by annealing under argon protection at 350℃ for 2 h.

[0056] Example 2: This example provides a method for preparing a positive electrode catalyst for a lithium-oxygen battery, including the following steps:

[0057] S1. Dissolve 2 mmol of iron salt, 1 mmol of cobalt salt and 16 mmol of sodium hydroxide in 7 mL of deionized water, stir well at room temperature, and then slowly add 10 mL of ethylenediamine to obtain a mixed solution.

[0058] S2. Stir the above mixed solution continuously for 30 minutes to form a black solution, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 105°C for 15 hours. After cooling to room temperature, centrifuge, wash and vacuum dry the precipitate to obtain the CFO carrier.

[0059] S3. The obtained ferrite support is treated at 145°C for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects.

[0060] S4. Disperse 100 mg of the defective CFO carrier in deionized water, and add 5 mL of K2PdCl6 aqueous solution (3 mg / mL). −1 Stir for 10 hours.

[0061] S5. Slowly add 3 mL of NaBH4 aqueous solution (5.5 mg / mL) −1 After stirring for 2 hours, the product was separated using a magnet, washed, and dried.

[0062] S6. The positive electrode catalyst (Pd / CFO) was obtained by annealing under argon protection at 340℃ for 2 hours.

[0063] Example 3: This example provides a method for preparing a positive electrode catalyst for a lithium-oxygen battery, including the following steps:

[0064] S1. Dissolve 4 mmol of iron salt, 2 mmol of cobalt salt and 16 mmol of sodium hydroxide in 7 mL of deionized water, stir well at room temperature, and then slowly add 12 mL of ethylenediamine to obtain a mixed solution.

[0065] S2. Stir the above mixed solution continuously for 30 minutes to form a black solution, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 115°C for 15 hours. After cooling to room temperature, centrifuge, wash and vacuum dry the precipitate to obtain the CFO carrier.

[0066] S3. The obtained ferrite support is treated at 155°C for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects.

[0067] S4. Disperse 100 mg of defective CFO carrier in deionized water, and add 5 mL of K2PdCl6 aqueous solution (3 mg / mL). −1 Stir for 10 hours.

[0068] S5. Slowly add 3 mL of NaBH4 aqueous solution (5.5 mg / mL) −1 After stirring for 2 hours, the product was separated using a magnet, washed, and dried.

[0069] S6. The positive electrode catalyst (Pd / CFO) was obtained by annealing under argon protection at 360℃ for 2 hours.

[0070] Comparative Example 1: This comparative example provides a method for preparing a palladium-on-carbon catalyst (Pd / C), which is the same as in Example 1, and specifically includes the following steps:

[0071] S1. Disperse 100 mg of carbon support in deionized water, and add 5 mL of K2PdCl6 aqueous solution (3 mg / mL). −1 Stir for 10 hours.

[0072] S2. Slowly add 3 mL of NaBH4 aqueous solution (5.5 mg / mL) −1 After stirring for 2 hours, centrifuge, wash and dry.

[0073] S3. The palladium-on-carbon catalyst (Pd / C) was obtained by annealing under argon protection at 350℃ for 2 h.

[0074] Comparative Example 2: This comparative example provides a method for preparing defective cobalt-iron ferrite (CFO), specifically including the following:

[0075] S1. Dissolve 4 mmol of iron salt, 2 mmol of cobalt salt and 20 mmol of sodium hydroxide in 7 mL of deionized water, stir well at room temperature, and then slowly add 14 mL of ethylenediamine to obtain a mixed solution.

[0076] S2. Stir the above mixed solution continuously for 30 minutes to form a black solution, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 110°C for 15 hours. After cooling to room temperature, centrifuge, wash and vacuum dry the precipitate to obtain the CFO carrier.

[0077] S3. The obtained ferrite support is treated at 150°C for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects.

[0078] Comparative Example 3: This comparative example provides a method for preparing Pd-loaded on a defect-free CFO support, specifically including the following:

[0079] S1. Dissolve 4 mmol of iron salt, 2 mmol of cobalt salt and 20 mmol of sodium hydroxide in 7 mL of deionized water, stir well at room temperature, and then slowly add 14 mL of ethylenediamine to obtain a mixed solution.

[0080] S2. Stir the above mixed solution continuously for 30 minutes to form a black solution, then transfer it to a polytetrafluoroethylene-lined autoclave and react at 110°C for 15 hours. After cooling to room temperature, centrifuge, wash and vacuum dry the precipitate to obtain the CFO carrier.

[0081] S3. Disperse 100 mg of CFO carrier in deionized water, and add 5 mL of K2PdCl6 aqueous solution (3 mg / mL). −1 Stir for 10 hours.

[0082] S4. Slowly add 3 mL of NaBH4 aqueous solution (5.5 mg / mL) −1 After stirring for 2 hours, the product was separated using a magnet, washed, and dried.

[0083] S5. The positive electrode catalyst (Pd / CFO) was obtained by annealing under argon protection at 350℃ for 2 h.

[0084] I. Structural Characterization: XRD patterns were analyzed of four defect-free materials: Pd / CFO prepared in Example 1, Pd / C prepared in Comparative Example 1, CFO prepared in Comparative Example 2, and Pd / CFO prepared in Comparative Example 3. The results were compared with those of the standard PDF card (PDF#03-0864) for CoFe2O4. Figure 1 As shown in the figure, the XRD pattern of CFO reveals multiple sharp and clear diffraction peaks, the positions of which perfectly match the characteristic peaks in the CoFe2O4 standard PDF card. The main diffraction peak positions are 30.2°, 35.6°, 43.5°, and 57.2°, corresponding to the (220), (311), (400), and (511) crystal planes of the CoFe2O4 spinel structure, respectively. This confirms that the synthesized CFO nanocrystals possess high crystallinity and a pure spinel phase. The defect-free XRD patterns of Pd / CFO, Pd / C, and Pd / CFO also show the presence of broad diffraction peaks for Pd. This clearly indicates that Pd nanoparticles have been successfully loaded and composited onto the support.

[0085] The Pd / C prepared in Comparative Example 1 and the CFO prepared in Comparative Example 2 were subjected to HRTEM testing, and the results are as follows: Figure 2As shown. From the HRTEM image of CFO, it can be seen that its crystal morphology is octahedral, the exposed crystal face is (111) crystal face, and the interplanar spacing is 4.87 Å. From the HRTEM image of Pd / C, it can be seen that Pd nanoparticles are clearly anchored on the surface of carbon support;

[0086] The Pd / CFO obtained in Example 1 was characterized by HAADF-STEM, as follows: Figure 3 As shown, Pd nanoparticles were found to be uniformly loaded on the CFO support, with an average size of approximately 3 nm.

[0087] The Pd / CFO obtained in Example 1 was characterized by HRTEM, as follows: Figure 4 As shown, HRTEM of Pd / CFO reveals a tight heterostructure between the (111) crystal plane of Pd and the (222) crystal plane of CFO, providing a structural basis for the generation of magnetism in Pd.

[0088] The Pd / CFO obtained in Example 1 was subjected to X-ray magnetic circular dichroism spectroscopy (MDS). This test has elemental resolution and can measure the magnetic properties of specific elements. The M value of Pd was also tested. 2,3 edge, such as Figure 5 As shown, the obvious circular dichroism signal at 559 eV proves that Pd in ​​Pd / CFO is induced to exhibit magnetism, which is beneficial to the catalytic reaction of lithium-oxygen batteries.

[0089] In summary, the characterization results of XRD and TEM consistently demonstrate that the embodiments of the present invention successfully synthesized CFO nanocrystals with high crystallinity, Pd / C, defect-free Pd / CFO, and Pd / CFO cathode catalyst. XMCD shows that Pd in ​​Pd / CFO is magnetic, laying the foundation for its excellent electrochemical performance in lithium-oxygen batteries.

[0090] II. Battery Assembly and Testing: The battery performance testing in this embodiment of the invention is based on a 2025 coin cell, and the electrode fabrication, battery assembly, and testing process are as follows:

[0091] Electrode fabrication: A slurry was prepared by uniformly mixing the positive electrode catalyst (Pd / CFO obtained in Examples 1, 2, and 3, or Pd / C obtained in Comparative Example 1, CFO obtained in Comparative Example 2, and Pd / CFO obtained in Comparative Example 3 without defects), Super P conductive additive, and polyvinylidene fluoride (PVDF) in an 80wt%:10wt%:10wt% mass ratio in N-methylpyrrolidone (NMP) solvent. The prepared slurry was sprayed onto carbon cloth to form a porous positive electrode. The coated carbon cloth was placed in a vacuum oven and dried at 80°C for 12 hours to completely remove residual solvent. The positive electrode catalyst loading on each piece of carbon cloth was approximately 0.6 mg.

[0092] Battery assembly: The negative electrode uses a thick lithium sheet; the separator uses glass fiber; the positive electrode uses the prepared carbon cloth coated with catalyst; the electrolyte uses a 1M LiTFSI / TEGDME solution; dimensions: negative electrode diameter 14 mm, separator diameter 16 mm, positive electrode diameter 12 mm. All battery assembly operations are performed in an argon (Ar) filled glove box.

[0093] Battery testing: The assembled lithium-oxygen batteries were rapidly transferred to oxygen-filled glass vials. Battery performance testing was conducted on a LAND CT2001A and NEWARE multi-channel battery testing system. The current density was 0.1 mA cm⁻¹. −1 Limited capacity 0.1mAh cm −2 The test environment was pure oxygen. The performance of the lithium-oxygen battery was as follows: Figure 4 As shown.

[0094] 1. The Pd / CFO cathode catalyst prepared in the embodiments of the present invention can significantly reduce the overpotential of lithium-oxygen batteries and improve the energy conversion efficiency: as shown in the appendix. Figure 6 As shown, in the lithium-oxygen battery test, the Pd / CFO used as the positive electrode catalyst in this embodiment of the invention exhibits a significantly smaller voltage hysteresis (i.e., overpotential) in its charge-discharge curve compared to Pd / C, CFO, and Pd / CFO without defects. This indicates that Pd / CFO can effectively accelerate the kinetics of ORR / OER, thereby reducing energy loss during charge-discharge and significantly improving the battery's energy conversion efficiency.

[0095] 2. The Pd / CFO cathode catalyst prepared in the embodiments of the present invention can significantly extend the cycle life of lithium-oxygen batteries: Figure 6 The test results show that Pd / CFO achieved stable cycling for up to 150 hours in lithium-oxygen batteries. This indicates that the Pd / CFO cathode catalyst prepared in the embodiments of the present invention significantly enhances the stability and durability of the cathode, effectively overcoming the shortcomings of poor stability of existing lithium-oxygen battery cathodes under high current densities.

[0096] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a positive electrode catalyst for a lithium-oxygen battery, characterized in that, Includes the following steps: S1: Dissolve 2-4 mmol of iron salt, 1-2 mmol of cobalt salt and 16-20 mmol of sodium hydroxide in 7 mL of deionized water, then add 7-14 mL of ethylenediamine to obtain a mixed solution, and react at 105-115℃ for 15 h to obtain a cobalt-iron ferrite support. S2: The cobalt-iron ferrite support obtained in S1 was heat-treated at 145-155℃ for 30 min under a 5% argon-hydrogen mixture to introduce oxygen defects. 100 mg of the obtained material was dispersed in 20 mL of deionized water. S3: Add a concentration of 2-4 mg / mL -1 A 5 mL palladium precursor solution was stirred for 10 hours, and then a 5.5 mg / mL solution was added. -1 A reducing agent with a volume of 3 mL was used to obtain a material supported on palladium nanoparticles, which was then annealed under argon protection at 340-360℃ for 2 h to obtain a positive electrode catalyst. The cathode catalyst consists of Pd nanoparticles supported on a subferromagnetic defect cobalt-iron ferrite, which induces the magnetism of Pd.

2. The application of the positive electrode catalyst of the lithium-oxygen battery obtained by the method for preparing the positive electrode catalyst of the lithium-oxygen battery according to claim 1 in the preparation of metal gas batteries.

3. The application according to claim 2, characterized in that, The battery is a lithium-oxygen battery, which includes a negative electrode, an electrolyte, and a positive electrode catalyst.

4. The application according to claim 3, characterized in that, The negative electrode is lithium; the electrolyte is lithium bis(trifluoromethanesulfonylimide) dissolved in tetraethylene glycol dimethyl ether; the positive electrode catalyst is coated on carbon cloth.

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