Heterojunction NiO-coated Fe2O3 / CC positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium oxygen batteries, in particular to a heterojunction type NiO-coated Fe2O3 / CC positive electrode material as well as a preparation method and application thereof. According to the preparation method, a two-step hydrothermal method is adopted to sequentially construct the vertically arranged Fe2O3 nanorod array and the NiO nanowire attached to the Fe2O3 nanorod array on the carbon cloth to form a unique three-dimensional hierarchical heterostructure, so that the specific surface area of the material is greatly increased, more active sites are exposed, and excellent conductivity and structural stability of the electrode are ensured; the NiO-coated Fe2O3p-n heterojunction and the three-dimensional hierarchical structure are adopted, so that the performance of the photo-assisted lithium oxygen battery is remarkably improved, and the overpotential of the battery under the illumination condition is remarkably reduced; the preparation method is simple and does not depend on precious metal, rare earth or selenide, through direct combination of the carbon cloth substrate and the active material, an excellent electron conduction path and structural stability are ensured, and the cycle life of the electrode is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to the field of lithium-oxygen battery technology, specifically to a heterojunction NiO@Fe2O3 / CC cathode material, its preparation method, and its application. Background Technology

[0002] The charging and discharging process of a lithium-oxygen battery is essentially an ORR and OER process, specifically manifested as the formation and decomposition of Li2O2. However, Li2O2 itself has poor conductivity and slow reversible formation and decomposition kinetics, resulting in high overpotentials, short cycle life, and low energy efficiency during actual operation.

[0003] Photo-assisted lithium-oxygen battery technology combines photoelectrocatalysis with electrochemical reactions. It utilizes light energy to excite the cathode catalyst, generating electron-hole pairs. Photogenerated electrons promote the formation of Li₂O₂ during the ORR (Organic Reduction) process, while photogenerated holes effectively drive the decomposition of Li₂O₂ during the OER (Organic Reduction) process, fundamentally reducing overpotential. However, existing technologies often rely on materials such as noble metals, rare earth elements, or selenides; the fabrication processes are complex; the electrode structures primarily use powder materials, requiring binders for film formation, which affects the electrode's conductivity and stability; and the efficient separation of photogenerated carriers still needs improvement. Summary of the Invention

[0004] In view of this, the present invention provides a heterojunction NiO@Fe2O3 / CC cathode material, its preparation method, and its application. The present invention combines two different semiconductor materials (p-type NiO and n-type Fe2O3) and utilizes the internal electric field formed at the interface to significantly promote the separation of photogenerated electron-hole pairs and regulate the surface electronic structure, thereby exposing more active sites and enhancing the material's activity.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a method for preparing a heterojunction NiO@Fe2O3 / CC cathode material, comprising the following steps: Iron source and mineralizer are dissolved in water and added to carbon cloth for the first hydrothermal reaction. After the reaction, the mixture is washed, dried and calcined for the first time to form an array of Fe2O3 nanorods (Fe2O3 / CC) on the carbon cloth. The nickel source and precipitant are dissolved in deionized water, and the resulting Fe2O3 / CC is added to carry out a second hydrothermal reaction. After the reaction, the mixture is washed, dried, and calcined a second time to obtain the final product.

[0006] Furthermore, the electrochemical activation treatment is carried out in an acidic electrolyte, with an applied voltage of 1.5~2.5 V and a treatment time of 0.5~3 min.

[0007] Furthermore, the iron source is ferric chloride, ferric nitrate, or ferric sulfate.

[0008] Furthermore, the mineralizing agent is sodium sulfate, sodium nitrate, or sodium chloride.

[0009] Furthermore, the molar ratio of the iron source to the mineralizing agent is 1:1 to 3.

[0010] The mineralizer selectively adsorbs onto the Fe2O3 crystal surface to regulate its directional growth. When the amount is appropriate, it forms a regular nanorod array; too little leads to insufficient directional growth, while too much causes excessive etching or structural collapse.

[0011] Furthermore, the temperature of the first hydrothermal reaction is 100~150 ℃, and the time is 4~8 h.

[0012] The hydrothermal temperature affects the nucleation and growth of Fe2O3 nanorods. When the temperature is too low, the crystallinity is insufficient and the nanorods are sparse and short. When the temperature is too high, the nanorods are too thick and the specific surface area decreases.

[0013] Furthermore, the first calcination temperature is 300~400 ℃, and the time is 1~3 h.

[0014] Furthermore, the nickel source is nickel nitrate, nickel chloride, or nickel sulfate.

[0015] Furthermore, the precipitant is urea or hexamethylenetetramine.

[0016] Furthermore, the molar ratio of the nickel source to the precipitant is 1:3~6.

[0017] The amount of precipitant determines the OH - When the release rate and dosage are appropriate, Ni 2+ Uniform deposition forms a complete coating; insufficient deposition results in low loading and poor coverage, while excessive deposition leads to NiO agglomeration and uneven coating, all of which weaken the heterojunction effect.

[0018] Furthermore, the temperature of the second hydrothermal reaction is 100~150 ℃, and the time is 4~8 h.

[0019] Second hydrothermal temperature control of urea hydrolysis and Ni 2+ Precipitation rate, Ni at excessively low temperatures 2+ Incomplete precipitation, low loading, and excessively rapid hydrolysis at high temperatures leading to NiO agglomeration all affect the integrity of the heterojunction interface.

[0020] Furthermore, the second calcination temperature is 300~400 ℃, and the time is 1~3 h.

[0021] Furthermore, the method also includes a carbon cloth pretreatment step, which specifically involves cleaning and electrochemically activating the carbon cloth. This carbon cloth pretreatment can enhance its surface activity and hydrophilicity.

[0022] In a second aspect, the present invention provides a heterojunction NiO@Fe2O3 / CC cathode material prepared by the preparation method described in the first aspect.

[0023] Furthermore, the heterojunction NiO@Fe2O3 / CC cathode material is a three-dimensional self-supporting NiO@Fe2O3 / CC heterostructure; the Fe2O3 nanorod array is vertically grown on carbon cloth fiber, and NiO nanowires are attached to the surface of Fe2O3 nanorods, together forming the heterojunction NiO@Fe2O3 / CC cathode material.

[0024] This invention effectively promotes the separation and migration of photogenerated carriers by constructing a NiO@Fe2O3 p-n heterojunction, achieving synergistic photoelectrocatalysis and significantly improving the kinetics of oxygen reduction and oxygen evolution reactions. The three-dimensional hierarchical structure composed of Fe2O3 nanorods and NiO nanosheets increases the active specific surface area, promoting electrolyte wetting and oxygen transport. At the same time, the self-supporting electrode avoids the use of binders, ensuring excellent conductivity and structural stability.

[0025] Thirdly, the present invention provides the application of the heterojunction NiO@Fe2O3 / CC cathode material described in the second aspect in the cathode of a photo-assisted lithium-oxygen battery.

[0026] Furthermore, the heterojunction NiO@Fe2O3 / CC cathode material is directly cut and used as a self-supporting cathode under light conditions.

[0027] Fourthly, the present invention provides a photo-assisted lithium-oxygen battery, wherein the positive electrode of the photo-assisted lithium-oxygen battery is the heterojunction NiO@Fe2O3 / CC positive electrode material described in the second aspect.

[0028] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The present invention uses a two-step hydrothermal method to sequentially construct a vertically arranged Fe2O3 nanorod array and NiO nanowires attached thereto on carbon cloth, forming a unique three-dimensional hierarchical heterostructure. This not only greatly increases the specific surface area of ​​the material and exposes more catalytic active sites, but also provides an ideal channel for electrolyte wetting and oxygen transport. At the same time, the self-supporting electrode form completely avoids the use of insulating binders, fundamentally ensuring the excellent conductivity and structural stability of the electrode.

[0029] (2) This invention achieves a significant improvement in the performance of light-assisted lithium-oxygen batteries by constructing a NiO@Fe2O3p-n heterojunction and a three-dimensional hierarchical structure. The built-in electric field formed at the interface of the two semiconductors effectively promotes the separation and migration of photogenerated electron-hole pairs, greatly improves the carrier utilization rate, and significantly reduces the overpotential of the battery under illumination conditions.

[0030] (3) This invention does not rely on expensive or special elements such as precious metals, rare earths or selenides, and the preparation process adopted abandons the complex steps of high-temperature selenization, phosphating, sol-gel in the prior art. The controllable growth of heterostructures can be achieved by simply adjusting the hydrothermal reaction parameters. The whole process is simple, green, reproducible and low cost, laying the foundation for large-scale production.

[0031] (4) The self-supporting electrode design of the present invention avoids the use of binders required by traditional powder catalysts. By directly combining the carbon cloth substrate with the active material, it ensures excellent electronic conduction path and structural stability, and significantly improves the cycle life of the electrode. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 The XRD patterns are of the materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention. Figure 2 This is a SEM image of NiO@Fe2O3 / CC obtained in Example 1 of the present invention. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0036] Example 1: A method for preparing a heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0037] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was then removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0038] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0039] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode perforated button cell. Assembly was performed in a glove box filled with high-purity argon (H2O and O2 concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe2O3 / CC positive electrode material prepared in this example, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket (Canrd), a spring sheet (Canrd), and a positive / negative electrode battery case (CR2032 perforated button cell case). The battery was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0040] Example 2: The difference between this embodiment and Embodiment 1 is that the temperature of the hydrothermal reaction was adjusted to explore the effects of different temperature conditions. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0041] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 100 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0042] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0043] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0044] Example 3: The difference between this embodiment and Embodiment 1 is that the temperature of the hydrothermal reaction was adjusted to explore the effects of different temperature conditions. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0045] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 150 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0046] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0047] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0048] Example 4: The difference between this embodiment and Embodiment 1 is that the calcination temperature was adjusted to explore the effects of different temperature conditions. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0049] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 400 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0050] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 400 °C for 2 h in air atmosphere to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0051] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0052] Example 5: The difference between this embodiment and Embodiment 1 is that the molar ratio of iron source to mineralizer is adjusted. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0053] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 6 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0054] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0055] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0056] Example 6: The difference between this embodiment and Embodiment 1 is that the molar ratio of nickel source to precipitant is adjusted. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0057] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was then removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0058] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 3 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air atmosphere to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0059] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0060] Example 7 The difference between this embodiment and Embodiment 1 is that the iron source and mineralizing agent, and the nickel source and precipitant are changed. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0061] (2) Preparation of Fe2O3 / CC: 2 mmol ferric nitrate and 4 mmol sodium nitrate were dispersed in 75 mL deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0062] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol nickel chloride and 5 mmol hexamethylenetetramine were dispersed in 75 mL deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air atmosphere to obtain heterojunction NiO@Fe2O3 / CC cathode material.

[0063] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). +A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0064] Example 8 The difference between this embodiment and Embodiment 1 is that the iron source and mineralizing agent, and the nickel source and precipitant are changed. The preparation method of the heterojunction NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0065] (2) Preparation of Fe2O3 / CC: 2 mmol ferric sulfate and 4 mmol sodium chloride were dispersed in 75 mL deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was then removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0066] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol nickel sulfate and 5 mmol hexamethylenetetramine were dispersed in 75 mL deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air atmosphere to obtain heterojunction NiO@Fe2O3 / CC cathode material.

[0067] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell button cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (a heterojunction NiO@Fe₂O₃ / CC positive electrode material prepared in this embodiment, a circle with a diameter of 16 mm), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0068] Comparative Example 1: A method for preparing a NiO / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0069] (2) Preparation of NiO / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the NiO / CC cathode material.

[0070] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (NiO / CC positive electrode material prepared in this comparative example, 16 mm in diameter), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings, placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0071] Comparative Example 2: A method for preparing Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0072] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC cathode material.

[0073] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of electrode sheets (Fe₂O₃ / CC positive electrode material prepared in this comparative example, 16 mm in diameter), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), lithium sheets, gaskets, spring sheets, and positive / negative electrode casings, placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0074] Comparative Example 3: This comparative example illustrates the performance difference between physical-mechanical mixing and the in-situ growth method of this invention. The preparation of NiO+Fe2O3 mechanically mixed / CC includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0075] (2) Fe2O3 nanorod powder and NiO nanosheet powder were synthesized by hydrothermal method and calcined at 350 °C for 2 h. The two powders were weighed at a Ni:Fe molar ratio of 1:2 (the same as the final elemental ratio in Example 1), physically mixed in a mortar and ground for 1 h. The mixed powder, acetylene black conductive agent and polyvinylidene fluoride binder were prepared into a slurry in N-methylpyrrolidone solvent at a mass ratio of 6:3:1, uniformly coated on the pretreated carbon cloth, and vacuum dried at 120 °C for 12 h to obtain the NiO + Fe2O3 mechanically mixed / CC electrode.

[0076] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of electrode sheets (materials prepared for this comparative example, 16 mm in diameter), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), lithium sheets, gaskets, spring sheets, and positive / negative electrode casings, placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0077] Comparative Example 4: A method for preparing NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0078] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 80 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0079] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0080] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (NiO@Fe₂O₃ / CC positive electrode material prepared in this comparative example, a 16 mm diameter circle), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0081] Comparative Example 5: A method for preparing NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0082] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was then removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 250 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0083] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 250 °C for 2 h in air atmosphere to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0084] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (NiO@Fe₂O₃ / CC positive electrode material prepared in this comparative example, a 16 mm diameter circle), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0085] Comparative Example 6: A method for preparing NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0086] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 1 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the carbon cloth was removed, repeatedly washed with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 350 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0087] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 5 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 350 °C for 2 h in air to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0088] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (NiO@Fe₂O₃ / CC positive electrode material prepared in this comparative example, a 16 mm diameter circle), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). +A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0089] Comparative Example 7: A method for preparing NiO@Fe2O3 / CC cathode material includes the following steps: (1) Carbon cloth pretreatment: Select a size of 3 × 4 cm 2 The carbon cloth was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 20 min each to thoroughly remove organic contaminants and impurities. Subsequently, in a three-electrode system (carbon cloth as the working electrode, Ag / AgCl electrode as the reference electrode, and platinum electrode as the counter electrode), the carbon cloth was electrochemically oxidized for 1 min at a constant voltage of 2.2 V using 1 M sulfuric acid solution as the electrolyte. After treatment, it was rinsed thoroughly with deionized water and dried in a vacuum drying oven at 50 °C to obtain the pretreated carbon cloth substrate.

[0090] (2) Preparation of Fe2O3 / CC: 2 mmol FeCl3·6H2O and 4 mmol Na2SO4 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min to ensure complete dissolution. The resulting solution was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, and a piece of pretreated carbon cloth was placed in the reactor to ensure complete immersion. The reactor was sealed and placed in an oven at 120 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The carbon cloth was then removed, washed repeatedly with deionized water, and dried at 60 °C. Finally, the sample was calcined in air at 250 °C for 2 h to obtain the Fe2O3 / CC intermediate.

[0091] (3) Preparation of NiO@Fe2O3 / CC: 1 mmol Ni(NO3)2·6H2O and 2 mmol CO(NH2)2 were dispersed in 75 mL of deionized water and magnetically stirred for 20 min. The solution was transferred to a 100 mL reactor, and the Fe2O3 / CC intermediate prepared in the previous step was added at the same time. The reactor was sealed and hydrothermally reacted in an oven at 120 °C for 6 h. After the reaction was completed, the sample was taken out, washed, and dried. Finally, it was calcined at 250 °C for 2 h in air atmosphere to obtain the heterojunction NiO@Fe2O3 / CC cathode material.

[0092] The assembly method of a positive electrode perforated button cell includes the following steps: The performance of the lithium-oxygen battery was evaluated using a positive electrode open-cell coin cell. Assembly was performed in a glove box filled with high-purity argon (H₂O and O₂ concentrations less than 0.1 ppm). The battery consisted of an electrode sheet (NiO@Fe₂O₃ / CC positive electrode material prepared in this comparative example, a 16 mm diameter circle), a glass fiber membrane permeated with electrolyte (120 μL 1M LiTFSI / TEGDME), a lithium sheet, a gasket, a spring sheet, and positive / negative electrode casings. It was placed in a saturated oxygen chamber and allowed to stand for 24 h. A multi-channel battery testing system (LAND CT2001A) was used, operating at 2.0–4.5 V (vs. Li / Li). + A series of constant current charge-discharge tests were conducted within the specified voltage window. During the tests, the xenon lamp was placed 15 cm above the battery housing, and the current was maintained at 15 A using a xenon lamp current stabilizer to ensure consistent test conditions. Simultaneously, a constant temperature chamber was used to maintain a constant battery temperature, preventing temperature-related effects on the battery.

[0093] Test Result Analysis Figure 1 These are the XRD patterns of the materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 1 As shown, no obvious impurity diffraction peaks were detected in the XRD pattern, indicating that high-purity Fe2O3 and NiO were successfully prepared during the hydrothermal synthesis process. Figure 2 This is a SEM image of NiO@Fe2O3 / CC obtained in Example 1 of this invention, as shown below. Figure 2 As shown, after secondary hydrothermal treatment, fine NiO nanowires are uniformly grown on the surface of each Fe2O3 nanorod, exhibiting a core-shell structure, and the introduction of NiO does not cause the collapse or cracking of Fe2O3.

[0094] The electrodes prepared in all the above embodiments and comparative examples were used as positive electrodes to assemble lithium-oxygen batteries, and their performance at a current density of 500 mA g was tested under both illuminated and dark conditions. -1 The discharge capacity at that time, and the fixed capacity of 500 mAh g -1 The overpotential during the first charge / discharge cycle was determined. The test results are shown in Table 1. Table 1. Lithium-oxygen battery performance of the cathode materials obtained in each embodiment and comparative example.

[0095] As shown in Table 1, the test results demonstrate that the NiO@Fe2O3p-n heterojunction constructed in this invention plays a decisive role in improving the performance of light-assisted lithium-oxygen batteries. In Example 1 (NiO@Fe2O3 / CC heterojunction), the overpotential significantly decreased to 0.62 V under illumination, and the discharge capacity increased to 12933 mAh cm⁻¹. -2 In contrast, Comparative Example 1 (single NiO / CC) exhibited a photo-induced overpotential as high as 1.33 V, with a discharge capacity of only 6730 mAh cm⁻¹. -2 Comparative Example 2 (single Fe2O3 / CC) had a photoluminescence overpotential of 1.37 V and a discharge capacity of only 7450 mAh cm⁻¹. -2 This indicates that when p-type NiO or n-type Fe2O3 is used alone, photogenerated electron-hole pairs recombine very easily, making it impossible to effectively utilize light energy to drive the ORR / OER reaction. However, when the two recombine to form a pn heterojunction, a built-in electric field is formed at the interface, which significantly promotes the separation and migration of photogenerated electron-hole pairs, further promoting the generation and decomposition of Li2O2, thereby fundamentally reducing the overpotential.

[0096] Further comparison of the test results of Example 1 and Comparative Example 3 shows that the two-step hydrothermal in-situ growth method used in this invention has significant advantages over the physical-mechanical mixing method. Although Comparative Example 3 (NiO + Fe2O3 mechanical mixing / CC) contains two semiconductor materials, it cannot form a tightly contacted heterojunction interface and uses an insulating binder. Therefore, it has a photo-induced overpotential of 1.25 V and a discharge capacity of 7135 mAh cm⁻¹. -2 The performance was far inferior to that of Example 1. This demonstrates that simply mixing the two materials cannot effectively construct a built-in electric field. The three-dimensional self-supporting heterojunction structure constructed by in-situ growth in this invention is the key to achieving performance improvement.

[0097] The performance of Examples 2-8 is slightly inferior to that of Example 1. This is mainly due to the subtle influence of hydrothermal reaction temperature, calcination temperature, raw material ratio and precursor type on crystal nucleation and growth kinetics. Specifically: In Examples 2 and 3, the low hydrothermal temperature may lead to insufficient growth and crystallinity of the nanorods, while the high temperature may cause excessive growth or uneven distribution of the nanorods, thereby reducing the effective heterojunction contact area; In Example 4, the increased calcination temperature, although not destroying the heterostructure, may cause slight coarsening of NiO grains, a reduction in active sites, and damage to the interface structure; In Example 5, the increased amount of mineralizer changed the ionic strength of the solution, interfering with the anisotropic growth of the nanorods, resulting in uneven distribution of nanorod diameters, and subsequent excessively thick local coating and local exposure during NiO loading, thus impairing the uniformity of the heterojunction; In Example 6, the insufficient amount of precipitant caused uneven NiO deposition, low coverage, and incomplete heterojunction; In Examples 7 and 8, after changing the type of reagent, the differences in the hydrolysis rate and coordination ability of different anions or organic molecules affected the release kinetics of the precursor, resulting in slight differences in the crystallinity or interface contact state of the heterojunction compared to Example 1.

[0098] Comparative Examples 4-7 outperformed the single material but lagged behind Example 1 and most Examples 2-8. In Comparative Example 4, the hydrothermal temperature of Fe2O3 was too low, far below the effective nucleation temperature range for nanorods, resulting in extremely poor Fe2O3 crystallinity, sparse array, and even large areas of exposed Fe2O3. This prevented the provision of a complete growth framework for NiO, making it difficult for subsequently grown NiO to form a continuous coating layer, significantly reducing the effective area of ​​the heterojunction. In Comparative Example 5, the calcination temperature was too low, far below the complete decomposition temperature of the NiO precursor, leading to residual organic matter and low crystallinity in NiO. The remaining impurities and defect states became recombination centers for photogenerated charge carriers, severely weakening the separation efficiency of the built-in electric field. In Comparative Example 6, the insufficient amount of mineralizer caused uncontrolled nanorod growth, resulting in a large number of particulate aggregates and a significant decrease in specific surface area. Even if NiO could be loaded, the usable heterojunction area was severely damaged. In Comparative Example 7, the insufficient amount of precipitant resulted in extremely low NiO nanowire loading and a large area of ​​missing coating layer, failing to form an effective core-shell heterostructure. The above results indicate that even if a heterojunction has been formed, if the process parameters deviate significantly from the optimal range, resulting in insufficient crystallinity, poor interfacial contact, a substantial reduction in active area, or a significant increase in carrier recombination centers, the actual effect of the built-in electric field will be severely weakened, preventing the performance from meeting expectations. This also confirms from the opposite perspective that constructing a high-quality heterojunction requires precise control of crystal nucleation and growth kinetics, interfacial contact state, and surface defect density to maximize the separation and utilization efficiency of photogenerated carriers.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a heterojunction NiO@Fe2O3 / CC cathode material, characterized in that, Includes the following steps: Iron source and mineralizer are dissolved in water, and carbon cloth is added to carry out the first hydrothermal reaction. After the reaction, the mixture is washed, dried and calcined for the first time to obtain Fe2O3 / CC. The nickel source and precipitant are dissolved in deionized water, and the resulting Fe2O3 / CC is added to carry out a second hydrothermal reaction. After the reaction, the mixture is washed, dried, and calcined a second time to obtain the final product.

2. The preparation method according to claim 1, characterized in that, The iron source is ferric chloride, ferric nitrate, or ferric sulfate; or the mineralizing agent is sodium sulfate, sodium nitrate, or sodium chloride.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the iron source to the mineralizing agent is 1:1 to 3.

4. The preparation method according to claim 1, characterized in that, The precipitant is urea or hexamethylenetetramine; or the nickel source is nickel nitrate, nickel chloride or nickel sulfate.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the nickel source to the precipitant is 1:3~6.

6. The preparation method according to claim 1, characterized in that, The temperature of the first hydrothermal reaction is 100~150℃ and the time is 4~8 h; or, the temperature of the first calcination is 300~400℃ and the time is 1~3 h.

7. The preparation method according to claim 1, characterized in that, The second hydrothermal reaction is carried out at a temperature of 100-150℃ for 4-8 hours; or the second calcination is carried out at a temperature of 300-400℃ for 1-3 hours.

8. The heterojunction NiO@Fe2O3 / CC cathode material prepared by the preparation method according to any one of claims 1 to 7, preferably, the Fe2O3 nanorod array is vertically grown on carbon cloth fiber, and the NiO nanowires are attached to the surface of the Fe2O3 nanorods.

9. The application of the heterojunction NiO@Fe2O3 / CC cathode material as described in claim 8 in the cathode of a photo-assisted lithium-oxygen battery.

10. A photo-assisted lithium-oxygen battery, characterized in that, The cathode of the light-assisted lithium-oxygen battery is the heterojunction NiO@Fe2O3 / CC cathode material as described in claim 8.

Images