Preparation method of copper-doped carbon nanofiber coated cerium-doped manganous oxide composite material as high-cycle-stability zinc positive electrode

Abstract

The invention belongs to the technical field of new energy materials, and relates to a preparation method for preparing a copper-doped carbon nanofiber coated cerium-doped manganous oxide composite material serving as a high-cycle-stability zinc positive electrode of an aqueous zinc ion battery by combining an electrostatic spinning method and high-temperature annealing.

Description

[0001] This invention belongs to the field of new energy materials technology, and relates to a method for preparing copper-doped carbon nanofiber-coated cerium-doped manganese oxide composite material as a high-cycle-stability zinc cathode for aqueous zinc-ion batteries by combining electrospinning and high-temperature annealing. Background Technology

[0002] With the deepening of global energy structure transformation and the "dual-carbon" strategy, the limitations of traditional lithium-ion batteries (LIBs) in the field of new energy storage are becoming increasingly apparent. This system is not only constrained by the strategic scarcity and price fluctuations of lithium resources, but also by the inherent flammability and thermal runaway risk of organic electrolytes, resulting in high costs for safety management throughout its entire lifecycle. Especially under extreme operating conditions or mechanical damage scenarios, LIBs pose risks of combustion and explosion, as well as electrolyte leakage, potentially causing serious secondary pollution. These issues significantly restrict their large-scale application in distributed energy storage, smart grids, and other scenarios.

[0003] Against this backdrop, aqueous zinc-ion batteries (AZIBs) have demonstrated significant breakthrough potential. AZIBs utilize abundant and inexpensive zinc as the negative electrode, circumventing the geopolitical constraints of lithium resources from the outset and providing a reliable resource foundation for large-scale industrialization. Simultaneously, the aqueous electrolyte possesses inherently non-flammable and non-toxic properties, significantly improving battery safety and reducing the cost of post-failure disposal and ecological restoration. Leveraging these advantages, AZIBs exhibit unique application value in stationary energy storage such as grid peak shaving, portable electronic devices, and applications with extremely high safety requirements, such as wearable medical devices and smart textiles.

[0004] However, the industrialization and marketization of AZIBs still face many challenges, especially the lagging development of high-performance cathode materials, which has become a core bottleneck restricting their promotion. Among various cathode materials, manganese-based materials are widely studied due to their high operating voltage, environmental friendliness, low cost, and structural diversity, making them one of the most promising directions. However, manganese oxide cathodes still suffer from structural instability caused by Jahn-Teller distortion, irreversible phase transitions during charge and discharge, low intrinsic conductivity, and slow reaction kinetics, resulting in poor cycle life and rate performance. To fully realize their potential as advanced cathode materials, it is necessary to systematically address the above challenges through material modification strategies. Currently, some studies have addressed the aforementioned issues by using carbon-coated manganese-based materials, doping with metal ions, and employing metal-organic frameworks. For example, Li et al. (Li, Zhang, et al. "Honeycomb-like MnO / C hybrids with strong interfacial interactions for aqueous zinc-ion batteries" RSC Advances 2025, 15, 5942) used metal-organic frameworks to embed MnO into a honeycomb carbon matrix, increasing its conductivity and stabilizing the cathode structure. He et al. (He, Pu, et al. "Carbonnanofiber-coated MnO composite as high-performance cathode material for aqueous zinc-ion batteries" Journal of Physics and Chemistry of Solids 184(2024) 111669) obtained MnO@CNFs by coaxial electrospinning to carbon-coat MnO followed by high-temperature annealing, thus improving the conductivity of the cathode material and preparing a high-performance zinc cathode.

[0005] To further improve the application of manganese-based materials in zinc cathodes, we propose a method for preparing copper-doped carbon nanofiber-coated cerium-doped manganese oxide composite materials as high-cycle-stability zinc cathodes by combining electrospinning and high-temperature annealing. The preparation method of cerium-doped manganese oxide composite material coated with copper-doped carbon nanofibers involves introducing Ce element into the MnO2 lattice through hydrothermal synthesis to generate the precursor Ce / MnOOH. Copper acetate (Cu(CH3COO)2·H2O) is then dissolved in a spinning solution of polyacrylonitrile (PAN) / N,N-dimethylformamide (DMF) to prepare the composite material of polymer nanofibers and precursor Ce / MnOOH using electrospinning technology. The final product, namely copper-doped carbon nanofiber coated cerium-doped manganese oxide electrode material (CeMnO / Cu-CNFs), is generated through pre-oxidation stabilization and high-temperature annealing. During the high-temperature annealing process, PAN nanofibers undergo graphitization transformation, while Cu(CH3COO)2·H2O is reduced at high temperature to generate copper-doped carbon nanofibers (Cu-CNFs), and Ce / MnOOH undergoes a high-temperature reduction reaction in the same process to become cerium-doped manganese oxide material (Ce / MnO). Using Ce as a dopant for MnO can effectively stabilize its crystal structure, mitigate the volume changes caused by zinc ion insertion / extraction, and reduce the risk of structural collapse. Simultaneously, Ce anchors manganese ions through strong bonding, inhibiting their dissolution in the electrolyte, thereby reducing active material loss and improving electrode cycle stability. As an abundant rare earth element, Ce also boasts advantages of low cost and high added value, helping to control overall preparation costs. On the other hand, Cu-doped carbon nanofibers (Cu-CNFs) can form a synergistic reinforcing system with CeMnO. The high conductivity of Cu combined with carbon nanofibers significantly reduces interfacial resistance and enhances overall electronic conductivity; simultaneously, Cu nanoparticles can act as high-speed electron channels, accelerating electron transport within the fiber network, thus significantly improving the electrode's rate performance. By encapsulating CeMnO in Cu-CNFs to construct a continuous, highly conductive carbon framework, a three-dimensional fast electron transport network can be established for CeMnO particles, effectively compensating for the insufficient intrinsic conductivity of MnO. This high aspect ratio structure overcomes the limitations of high resistance and low transport efficiency caused by traditional point-to-point contact between nanoparticles. Furthermore, the carbon coating isolates MnO from direct contact with the electrolyte, further suppressing manganese dissolution and volume effects. Simultaneously, the uniformly dispersed Cu nanoparticles provide more pathways for ion diffusion, positively impacting ion diffusion kinetics. Summary of the Invention

[0006] (1) Synthesis of precursor Ce / MnOOH

[0007] A certain amount of MnO2 and Ce(NO3)3 were weighed and dispersed in 50 ml of deionized water, and stirred with a magnetic stirrer for 4 hours. The mixture was then transferred to a 100 ml hydrothermal reactor and subjected to a hydrothermal reaction in an electrically heated constant-temperature drying oven at 160°C for 72 hours. After the reactor cooled down and the hydrothermal reaction was complete, the target product was separated using a high-speed centrifuge and washed three times each with deionized water and ethanol. Finally, the target product was transferred to an electrically heated constant-temperature drying oven at 60°C for 12 hours. The resulting brownish-black powder was the target product Ce / MnOOH.

[0008] (2) Preparation of electrospinning solution

[0009] Weigh 0.05–0.15 g of Cu(CH3COO)2·H2O and disperse it in 3 ml of N,N-dimethylformamide (DMF) solution. Stir with a magnetic stirrer until Cu(CH3COO)2·H2O is completely dissolved in the DMF solution. Then add 0.5 g of Ce / MnOOH and ultrasonically disperse the solution using an ultrasonic cleaner for 1 h. Then add 0.3 g of PAN powder and transfer the solution to a magnetic stirrer for 12 h until the solution becomes a homogeneous, viscous, brownish-black solution.

[0010] (3) Preparation of precursor polymer nanofibers

[0011] Transfer the prepared mixed spinning solution into a 5ml disposable syringe, and spin using a flat-tipped spinning needle (23g). Place the syringe on the electrospinning injection platform, and set the injection speed to 0.082mm / min. -1 The translation speed is 200.0 mm / min. -1 The distance between the spinning collection plate and the needle tip is 18.0 cm. The working voltage is set as follows: positive high voltage of 10-15KV for the nozzle and negative high voltage of -1.50KV for the collection plate. The surface of the collection plate is covered with aluminum foil, and the electrospun fiber membrane is collected on the aluminum foil. After spinning, the aluminum foil with the polymer nanofiber membrane is transferred to an electric thermostatic drying oven. The temperature is set to 60℃ and the drying time is 12h to remove residual DMF from the fiber membrane.

[0012] (4) High-temperature post-treatment

[0013] The electrospun fiber membrane was pre-oxidized in air using an atmosphere-controlled tubular furnace at a temperature of 260°C and a heating rate of 1°C / min. -1 The heat treatment time was 420 min. The pre-oxidized fiber membrane was then subjected to high-temperature annealing at an Ar atmosphere of 700–1000 °C with a heating rate of 1 °C / min. -1The heat treatment time was 180 min to obtain the final product CeMnO / Cu-CNFs composite electrode material.

[0014] According to the present invention, preferably, the optimal addition amounts of MnO2 and Ce(NO3)3 in step (1) are 0.8694g and 0.8684g, respectively, wherein Mn:Ce = 10:1.

[0015] According to the present invention, preferably, the optimal addition amount of Cu(CH3COO)2·H2O in step (2) is 0.1g. According to the present invention, preferably, the optimal positive voltage of the spinning nozzle in step (3) is 13.5KV.

[0016] According to the present invention, preferably, the Ar atmosphere temperature in step (4) is set to 900°C.

[0017] Description of attached figures and tables

[0018] Figure 1 The X-ray diffraction patterns are those of CeMnO / Cu-CNFs and the comparative CeMnO electrode material prepared in Example 1 of this invention.

[0019] Figure 2 This is a scanning electron microscope image of the CeMnO / Cu-CNFs electrode material prepared in Example 1 of the present invention.

[0020] Figure 3 This is a scanning electron microscope image of the CeMnO electrode material prepared in the comparative example of this invention.

[0021] Figure 4 This is a projection microscope image of the CeMnO / Cu-CNFs electrode material prepared in Example 1 of the present invention.

[0022] Figure 5 This is a projection microscope image of the CeMnO electrode material prepared in the comparative example of this invention.

[0023] Figure 6 The electrochemical performance diagrams are shown for the CeMnO / Cu-CNFs series electrode materials prepared in Example 1 of this invention and the electrochemical performance diagrams for the CeMnO electrode materials prepared in the comparative example. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto. Furthermore, the experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0025] Example 1:

[0026] Weigh out 0.8694 g of MnO2 and 0.8684 g of Ce(NO3)3 and disperse them in 50 ml of deionized water (Mn:Ce = 10:1). Stir with a magnetic stirrer for 4 h. Transfer to a 100 ml hydrothermal reactor and carry out the hydrothermal reaction in an electrically heated constant-temperature drying oven at 160 °C for 72 h. After the reactor cools down and the hydrothermal reaction is complete, separate the target product using a high-speed centrifuge and wash three times with deionized water and ethanol respectively. Finally, transfer the target product to an electrically heated constant-temperature drying oven for drying at 60 °C for 12 h. The resulting brownish-black powder is the target product Ce / MnOOH.

[0027] Weigh 0.1 g of Cu(CH3COO)2·H2O and disperse it in 3 ml of N,N-dimethylformamide (DMF) solution. Stir with a magnetic stirrer until Cu(CH3COO)2·H2O is completely dissolved in the DMF solution. Then add 0.5 g of Ce / MnOOH and ultrasonically disperse the solution for 1 h. Then add 0.3 g of PAN powder and transfer the solution to a magnetic stirrer for 12 h until the solution becomes a homogeneous, viscous, brownish-black solution.

[0028] Transfer the prepared mixed spinning solution into a 5ml disposable syringe, and spin using a flat-tipped spinning needle (23g). Place the syringe on the electrospinning injection platform, and set the injection speed to 0.082mm / min. -1 The translation speed is 200.0 mm / min. -1 The distance between the spinning collection plate and the needle tip is 18.0 cm. The working voltage is set as follows: positive high voltage of 13.50 KV for the nozzle and negative high voltage of -1.50 KV for the collection plate. The surface of the collection plate is covered with aluminum foil, and the electrospun fiber membrane is collected on the aluminum foil. After spinning, the aluminum foil with the polymer nanofiber membrane is transferred to an electric thermostatic drying oven. The temperature is set to 60℃ and the drying time is 12 hours to remove residual DMF from the fiber membrane.

[0029] The electrospun fiber membrane was pre-oxidized in air using an atmosphere-controlled tubular furnace at a temperature of 260°C and a heating rate of 1°C / min. -1 The heat treatment time was 420 min. The pre-oxidized fiber membrane was then subjected to high-temperature annealing at 900℃ in an Ar atmosphere with a heating rate of 1℃ / min. -1 The heat treatment time was 180 min to obtain the final product CeMnO / Cu-CNFs composite electrode material.

[0030] Example 2:

[0031] Weigh out 0.8694 g of MnO2 and 0.8684 g of Ce(NO3)3 and disperse them in 50 ml of deionized water (Mn:Ce = 10:1). Stir with a magnetic stirrer for 4 h. Transfer to a 100 ml hydrothermal reactor and carry out the hydrothermal reaction in an electrically heated constant-temperature drying oven at 160 °C for 72 h. After the reactor cools down and the hydrothermal reaction is complete, separate the target product using a high-speed centrifuge and wash three times with deionized water and ethanol respectively. Finally, transfer the target product to an electrically heated constant-temperature drying oven for drying at 60 °C for 12 h. The resulting brownish-black powder is the target product Ce / MnOOH.

[0032] Weigh 0.15g of Cu(CH3COO)2·H2O and disperse it in 3ml of N,N-dimethylformamide (DMF) solution. Stir with a magnetic stirrer until Cu(CH3COO)2·H2O is completely dissolved in the DMF solution. Then add 0.5g of Ce / MnOOH and ultrasonically disperse the solution for 1h. Then add 0.3g of PAN powder and transfer the solution to a magnetic stirrer for 12h until the solution becomes a homogeneous, viscous, brownish-black solution.

[0033] Transfer the prepared mixed spinning solution into a 5ml disposable syringe, and spin using a flat-tipped spinning needle (23g). Place the syringe on the electrospinning injection platform, and set the injection speed to 0.082mm / min. -1 The translation speed is 200.0 mm / min. -1 The distance between the spinning collection plate and the needle tip is 18.0 cm. The working voltage is set as follows: positive high voltage of 13.50 KV for the nozzle and negative high voltage of -1.50 KV for the collection plate. The surface of the collection plate is covered with aluminum foil, and the electrospun fiber membrane is collected on the aluminum foil. After spinning, the aluminum foil with the polymer nanofiber membrane is transferred to an electric thermostatic drying oven. The temperature is set to 60℃ and the drying time is 12 hours to remove residual DMF from the fiber membrane.

[0034] The electrospun fiber membrane was pre-oxidized in air using an atmosphere-controlled tubular furnace at a temperature of 260°C and a heating rate of 1°C / min. -1 The heat treatment time was 420 min. The pre-oxidized fiber membrane was then subjected to high-temperature annealing at 900℃ in an Ar atmosphere with a heating rate of 1℃ / min. -1 The heat treatment time was 180 min to obtain the final product CeMnO / Cu-CNFs composite electrode material.

[0035] Example 3:

[0036] Weigh out 0.8694 g of MnO2 and 0.8684 g of Ce(NO3)3 and disperse them in 50 ml of deionized water (Mn:Ce = 10:1). Stir with a magnetic stirrer for 4 h. Transfer to a 100 ml hydrothermal reactor and carry out the hydrothermal reaction in an electrically heated constant-temperature drying oven at 160 °C for 72 h. After the reactor cools down and the hydrothermal reaction is complete, separate the target product using a high-speed centrifuge and wash three times with deionized water and ethanol respectively. Finally, transfer the target product to an electrically heated constant-temperature drying oven for drying at 60 °C for 12 h. The resulting brownish-black powder is the target product Ce / MnOOH.

[0037] Weigh 0.2 g of Cu(CH3COO)2·H2O and disperse it in 3 ml of N,N-dimethylformamide (DMF) solution. Stir with a magnetic stirrer until Cu(CH3COO)2·H2O is completely dissolved in the DMF solution. Then add 0.5 g of Ce / MnOOH and ultrasonically disperse the solution for 1 h. Then add 0.3 g of PAN powder and transfer the solution to a magnetic stirrer for 12 h until the solution becomes a homogeneous, viscous, brownish-black solution.

[0038] Transfer the prepared mixed spinning solution into a 5ml disposable syringe, and spin using a flat-tipped spinning needle (23g). Place the syringe on the electrospinning injection platform, and set the injection speed to 0.082mm / min. -1 The translation speed is 200.0 mm / min. -1 The distance between the spinning collection plate and the needle tip is 18.0 cm. The working voltage is set as follows: positive high voltage of 13.50 KV for the nozzle and negative high voltage of -1.50 KV for the collection plate. The surface of the collection plate is covered with aluminum foil, and the electrospun fiber membrane is collected on the aluminum foil. After spinning, the aluminum foil with the polymer nanofiber membrane is transferred to an electric thermostatic drying oven. The temperature is set to 60℃ and the drying time is 12 hours to remove residual DMF from the fiber membrane.

[0039] The electrospun fiber membrane was pre-oxidized in air using an atmosphere-controlled tubular furnace at a temperature of 260°C and a heating rate of 1°C / min. -1 The heat treatment time was 420 min. The pre-oxidized fiber membrane was then subjected to high-temperature annealing at 900℃ in an Ar atmosphere with a heating rate of 1℃ / min. -1 The heat treatment time was 180 min to obtain the final product CeMnO / Cu-CNFs composite electrode material.

[0040] Comparative example:

[0041] After the precursor Ce / MnOOH was synthesized, it was not involved in electrospinning and was directly annealed at high temperature in a tube furnace with the annealing parameters unchanged, to obtain the comparative product CeMnO.

Claims

1. A method for preparing a copper-doped carbon nanofiber-coated cerium-doped manganese oxide composite material (CeMnO / Cu-CNFs) as a high-stability cycling electrode material, characterized in that, The fiber morphology and composition ratio are controlled by adjusting the spinning solution ratio, annealing temperature, and working parameters during the electrospinning process.

2. A method for preparing the energy storage cathode material as described in claim 1, characterized in that, Includes steps. Step 1: Weigh a certain amount of MnO2 and Ce(NO3)3 and disperse them in 50 ml of deionized water. Stir with a magnetic stirrer for 4 hours. Transfer to a 100 ml hydrothermal reactor and carry out a hydrothermal reaction in an electrically heated constant-temperature drying oven at 160℃ for 72 hours. After the reactor cools down and the hydrothermal reaction is complete, separate the target product using a high-speed centrifuge. Wash the product three times with deionized water and ethanol, respectively. Finally, transfer the target product to an electrically heated constant-temperature drying oven at 60℃ for 12 hours. The resulting brownish-black powder is the target product Ce / MnOOH. Step 2: Weigh 0.05-0.15g of Cu(CH3COO)2·H2O and disperse it in 3ml of N,N-dimethylformamide (DMF) solution. Stir with a magnetic stirrer until Cu(CH3COO)2·H2O is completely dissolved in the DMF solution. Then add 0.5g of Ce / MnOOH and use an ultrasonic cleaner to ultrasonically disperse the solution for 1 hour. Then add 0.3g of PAN powder and transfer the solution to a magnetic stirrer for 12 hours until the solution becomes a uniform brownish-black viscous solution. Step 3: Transfer the prepared mixed spinning solution to a 5ml disposable syringe, and spin using a flat-tipped spinning needle (23g). Place the syringe on the electrospinning injection platform, and set the injection speed to 0.082mm / min. -1 The translation speed is 200.0 mm / min. -1 The distance between the spinning collection plate and the needle tip is 18.0 cm. The working voltage is set as follows: positive high voltage of 10-15KV for the nozzle and negative high voltage of -1.50KV for the collection plate. The surface of the collection plate is covered with aluminum foil, and the electrospun fiber membrane is collected on the aluminum foil. After spinning, the aluminum foil with the polymer nanofiber membrane is transferred to an electric thermostatic drying oven. The temperature is set to 60℃ and the drying time is 12h to remove residual DMF from the fiber membrane. Step 4: Pre-oxidize the electrospun fiber membrane in air using an atmosphere tube furnace at a temperature of 260℃ and a heating rate of 1℃ / min. -1 The heat treatment time was 420 min. The pre-oxidized fiber membrane was then subjected to high-temperature annealing at an Ar atmosphere of 700–1000 °C with a heating rate of 1 °C / min. -1 The heat treatment time was 180 min to obtain the final product CeMnO / Cu-CNFs composite electrode material.

3. The preparation method according to claim 2, characterized in that, In step one, the optimal addition amounts of MnO2 and Ce(NO3)3 are 0.8694g and 0.8684g, respectively, where Mn:Ce = 10:

1.

4. The preparation method according to claim 2, characterized in that, The optimal addition amount of Cu(CH3COO)2·H2O in step two is 0.1g.

5. The preparation method according to claim 2, characterized in that, In step three, the optimal positive high voltage for the spinning nozzle is 13.5KV.

6. The preparation method according to claim 2, characterized in that, In step four, the optimal temperature setting for the Ar atmosphere is 900℃.

7. The application of the CeMnO / Cu-CNFs composite electrode material according to claim 7 in an aqueous zinc-ion battery, characterized in that, The CeMnO / Cu-CNFs composite electrode material prepared by the method described in claim 1 is used as the positive electrode, the polished zinc foil is used as the negative electrode, the separator is a GF / D type glass fiber separator, and the electrolyte is an aqueous solution of zinc sulfate.

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