Preparation method of cerium-doped MnCO3-Mn2O3 composite material

Abstract

The invention discloses a preparation method of a cerium-doped MnCO3-Mn2O3 composite material, and belongs to the technical field of aqueous zinc ion batteries. The preparation method comprises the following steps: dissolving a manganous nitrate aqueous solution, urea and cerium nitrate hexahydrate in purified water, and carrying out hydrothermal reaction, filtering, drying and calcining treatment to obtain the cerium-doped MnCO3-Mn2O3 composite material. The microstructure shows that the composite material is composed of micron-sized blocky cubes and spherical-like particles stacked by sheet layers, the micron-sized blocky cubes and the spherical-like particles are consistent in orientation and provided with triangular pyramid-shaped protrusions, and the spherical-like nanoparticles of 50-200 nm are evenly anchored on the surfaces and in gaps of the composite material. The directional anchoring structure is beneficial to construction of a continuous electron conduction network and exposure of a rich active interface to form a stable cerium-doped double-phase composite system, so that the reaction kinetic performance of an electrode is remarkably improved, and the electrochemical performance of the composite material is improved.

Description

Technical Field

[0001] This invention discloses a method for preparing cerium-doped MnCO3-Mn2O3 composite material, belonging to the field of aqueous zinc-ion battery technology. Background Technology

[0002] As the global energy structure shifts towards sustainability, developing efficient, safe, and low-cost electrochemical energy storage systems has become one of the core challenges in the field of energy technology. Among numerous energy storage technologies, lithium-ion batteries, while dominating the consumer electronics and electric vehicle markets, face inherent limitations such as limited lithium resources, rising costs, and the flammability and explosiveness of organic electrolytes. In contrast, aqueous zinc-ion batteries, due to their high safety, low cost, and environmental friendliness, are considered to have broad application prospects in large-scale energy storage. However, the commercialization of aqueous zinc-ion batteries is largely limited by the development of cathode materials. Among numerous candidate materials, manganese-based oxides have always been the main research focus for cathode materials in energy storage systems due to their advantages such as multiple valence states, high theoretical capacity, abundant resources, and non-toxicity. However, they still face severe challenges in practical applications, the most significant being the degradation of Mn. 3+ The Jahn-Teller effect can lead to severe structural distortion and capacity decay during charging and discharging.

[0003] To overcome the bottlenecks in the application of manganese-based oxides as cathodes in aqueous zinc-ion batteries, researchers have proposed various strategies, mainly including nanostructure design, material composites, and ion doping. In recent years, rare earth element doping has shown unique advantages in electrocatalysis, energy storage batteries, and other fields. During the doping process, rare earth elements can introduce lattice strain, regulate band structure, promote oxygen vacancy formation, and may enhance the redox activity and structural robustness of materials through synergistic effects with host metals. Among them, the rare earth element cerium possesses... 3+ / Ce 4+ Reversible redox pairs have great potential in improving the cycling stability and reaction kinetics of electrode materials. Summary of the Invention

[0004] To address the challenges of using manganese-based materials as cathode materials in aqueous zinc-ion batteries, this invention provides a method for preparing cerium-doped MnCO3-Mn2O3 composite materials. The method involves dissolving an aqueous solution of manganese nitrate, urea, and cerium nitrate hexahydrate in purified water, followed by hydrothermal reaction, filtration, drying, and calcination to obtain the cerium-doped MnCO3-Mn2O3 composite material. This synthesis method is simple, low-cost, and suitable for large-scale industrial production.

[0005] The cerium-doped MnCO3-Mn2O3 composite material of the present invention is characterized by the following: XRD diffraction peaks at 24.5°, 31.65°, 33.14° and 55.33°; XPS peaks at 288.77 eV, 529.02 eV, 530.98 eV, 641.72 eV, 653.10 eV, 884.46 eV and 916.3 eV, with cerium exhibiting both +3 and +4 valences, and manganese exhibiting both +2 and +3 valences.

[0006] The present invention also provides a method for preparing the cerium-doped MnCO3-Mn2O3 composite material, comprising the following steps:

[0007] The first step is to disperse the manganese nitrate aqueous solution in deionized water, then add urea and cerium nitrate hexahydrate in sequence, and stir until well mixed.

[0008] The second step is to place the well-stirred solution into a hydrothermal reactor, react it at a constant temperature in an oven, and then allow it to cool down naturally.

[0009] The third step is to remove the product from the hydrothermal reactor, wash and filter it, and then put it into an oven to dry.

[0010] The fourth step involves calcination in a muffle furnace followed by cooling to obtain cerium-doped MnCO3-Mn2O3 composite material.

[0011] Furthermore, in the above technical solution, in the first step, the molar ratio of manganese nitrate to urea is 19:60.

[0012] Furthermore, in the above technical solution, in the first step, the molar ratio of manganese nitrate and cerium nitrate hexahydrate is 19:1.

[0013] Furthermore, in the above technical solution, in the second step, the constant temperature reaction temperature is 160℃, and the constant temperature reaction time is 6 hours.

[0014] Furthermore, in the above technical solution, in the third step, the reaction product is cleaned with pure water. The reaction product is placed in pure water to form a suspension, and then ultrasonically cleaned for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of 5 times.

[0015] Furthermore, in the above technical solution, in the third step, the drying temperature is 80℃ and the drying time is 1.5 hours.

[0016] Furthermore, in the above technical solution, in the fourth step, the calcination temperature is 450℃, and the constant temperature calcination time is 5 hours, of which the heating program is set for 2 hours and the cooling to below 200℃ for 2 hours.

[0017] This invention also provides the application of cerium-doped MnCO3-Mn2O3 composite materials in aqueous zinc-ion batteries.

[0018] Beneficial effects of the invention:

[0019] 1. This invention prepares cerium-doped MnCO3-Mn2O3 composite materials. The raw materials used are inexpensive, the synthesis method is simple, and the entire preparation process is low-polluting, meeting the requirements of green environmental protection.

[0020] 2. This method improves the electrochemical performance of MnCO3-Mn2O3 composite materials through cerium doping. The material consists of micron-sized blocky cubes with uniform orientation and triangular pyramidal protrusions, and stacked spherical particles. Spherical nanoparticles of 50–200 nm are uniformly anchored on its surface and in the gaps, forming a stable cerium-doped biphase composite system.

[0021] 3. The above-mentioned directional anchoring structure is conducive to building a continuous electron conduction network and exposing abundant active interfaces, thereby effectively improving electrode reaction kinetics and enhancing the overall electrochemical performance of the composite material. Attached Figure Description

[0022] Figure 1 The image shows the XRD pattern of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of this invention.

[0023] Figure 2 The images shown are SEM images of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of the present invention; wherein: (a) is a SEM image of a blocky cube; (b) is a SEM image of a near-spherical particle.

[0024] Figure 3 XPS spectra of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of this invention; wherein: (a) is the full XPS spectrum; (b) is the XPS spectrum of Ce3d; (c) is the XPS spectrum of Mn2p; (d) is the XPS spectrum of O1s; and (e) is the XPS spectrum of C1s.

[0025] Figure 4 This is the EDS image of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of the present invention;

[0026] Figure 5 The image shows the elemental distribution of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of this invention; where: (a) is the elemental distribution of Ce; (b) is the elemental distribution of Mn; (c) is the elemental distribution of O; and (d) is the elemental distribution of C.

[0027] Figure 6The infrared spectrum of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of this invention;

[0028] Figure 7 The image shows the Raman spectrum of the cerium-doped MnCO3-Mn2O3 composite material in Example 4 of this invention.

[0029] Figure 8 This is a cyclic charge-discharge diagram of the cerium-doped MnCO3-Mn2O3 composite material in Example 5 of the present invention;

[0030] Figure 9 The cyclic voltammogram of the cerium-doped MnCO3-Mn2O3 composite material in Example 5 of this invention;

[0031] Figure 10 The image shows the AC impedance diagram of the cerium-doped MnCO3-Mn2O3 composite material in Example 5 of this invention. Detailed Implementation

[0032] The present invention is further described below through specific examples. However, these examples are merely exemplary and are not limited to the scope of protection of the present invention; they are merely embodiments.

[0033] In the following embodiments, unless otherwise specified, the reagents, materials and instruments used are all conventional reagents, materials and instruments, and are commercially available. The reagents involved can also be synthesized by conventional synthesis methods.

[0034] Example 1

[0035] First, weigh 8.5037g of 50% manganese nitrate aqueous solution and 4.3243g of urea, dissolve them in 60mL of purified water, and stir for 0.5 hours.

[0036] The second step is to add 0.1042g of cerium nitrate hexahydrate to the well-mixed solution and stir for 1 hour.

[0037] The third step is to put the above-mentioned well-stirred mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 6 hours, followed by natural cooling.

[0038] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. A total of 5 cleaning operations are performed.

[0039] Fifth step: Place the cleaned and filtered product into an oven and dry at 80°C for 1.5 hours.

[0040] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the furnace is cooled to obtain the cerium-doped MnCO3-Mn2O3 composite material. The calcination temperature is 450℃, with a heating program set for 2 hours, a cooling program to below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.

[0041] Example 2

[0042] First, weigh 8.4178g of 50% manganese nitrate aqueous solution and 4.3243g of urea, dissolve them in 60mL of purified water, and stir for 0.5 hours.

[0043] The second step is to add 0.2084g of cerium nitrate hexahydrate to the well-mixed solution and stir for 1 hour.

[0044] The third step is to put the above-mentioned well-stirred mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 6 hours, followed by natural cooling.

[0045] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. A total of 5 cleaning operations are performed.

[0046] Fifth step: Place the cleaned and filtered product into an oven and dry at 80°C for 1.5 hours.

[0047] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the furnace is cooled to obtain the cerium-doped MnCO3-Mn2O3 composite material. The calcination temperature is 450℃, with a heating program set for 2 hours, a cooling program to below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.

[0048] Example 3

[0049] First, weigh 8.3319g of 50% manganese nitrate aqueous solution and 4.3243g of urea, dissolve them in 60mL of purified water, and stir for 0.5 hours.

[0050] The second step is to add 0.3127g of cerium nitrate hexahydrate to the well-mixed solution and stir for 1 hour.

[0051] The third step is to put the above-mentioned well-stirred mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 6 hours, followed by natural cooling.

[0052] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. A total of 5 cleaning operations are performed.

[0053] Fifth step: Place the cleaned and filtered product into an oven and dry at 80°C for 1.5 hours.

[0054] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the furnace is cooled to obtain the cerium-doped MnCO3-Mn2O3 composite material. The calcination temperature is 450℃, with a heating program set for 2 hours, a cooling program to below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.

[0055] Example 4

[0056] First, weigh 8.1601g of 50% manganese nitrate aqueous solution and 4.3243g of urea, dissolve them in 60mL of purified water, and stir for 0.5 hours.

[0057] The second step is to add 0.5211g of cerium nitrate hexahydrate to the well-mixed solution and stir for 1 hour.

[0058] The third step is to put the above-mentioned well-stirred mixed solution into a hydrothermal reactor and react it at a constant temperature of 160°C in an oven for 6 hours, followed by natural cooling.

[0059] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. Use pure water to clean and filter the reaction product, place the reaction product in pure water to form a suspension, and sonicate it in an ultrasonic cleaner for 3 minutes. Then filter the suspension. A total of 5 cleaning operations are performed.

[0060] Fifth step: Place the cleaned and filtered product into an oven and dry at 80°C for 1.5 hours.

[0061] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the furnace is cooled to obtain the cerium-doped MnCO3-Mn2O3 composite material. The calcination temperature is 450℃, with a heating program set for 2 hours, a cooling program to below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.

[0062] Figure 1The XRD pattern of the cerium-doped MnCO3-Mn2O3 composite material is shown. All diffraction peaks are assigned to rhombohedral MnCO3 (PDF#04-011-3970) and orthorhombic Mn2O3 (PDF#04-007-0856), and no impurity phase peaks are observed. The peaks at 24.5° and 31.65° correspond to the (012) and (104) crystal planes of the MnCO3 phase. The peaks at 33.14° and 55.33° correspond to the (222) and (404) crystal planes of the Mn2O3 phase.

[0063] Figure 2 The image shows a SEM image of the cerium-doped MnCO3-Mn2O3 composite material. The image reveals that the material consists of uniformly oriented, micron-sized blocky cubes with triangular pyramidal protrusions and stacked, spherical particles. Spherical nanoparticles of 50–200 nm are uniformly anchored on the surface and in the interstices. This oriented anchoring structure facilitates the construction of a continuous electron conduction network and exposes abundant active interfaces, forming a stable cerium-doped biphase composite system. This significantly improves the electrode reaction kinetics and enhances the electrochemical performance of the composite material.

[0064] Figure 3 XPS image of cerium-doped MnCO3-Mn2O3 composite material. Figure 3 The full spectrum in (a) confirms that the material surface is mainly composed of Mn, O, C, and Ce elements, with no other impurity elements detected. High-resolution spectrum of Ce 3d... Figure 3 The fitting analysis in (b) shows that Ce exists in a mixed +3 and +4 valence state. The characteristic peaks with binding energies of 882.0 eV, 888.49 eV, 897.89 eV, 905.42 eV, and 916.3 eV are attributed to Ce. 4+ The peaks at 884.46 eV and 900.72 eV correspond to Ce. 3+ . Figure 3 The Mn 2p spectrum in (c) shows that Mn 2p 3 / 2 and Mn 2p 1 / 2 The main peaks are located at 641.72 eV and 653.10 eV, respectively. This was achieved through analysis of Mn2p... 3 / 2 Peak fitting revealed two sub-peaks at 641.3 eV and 643.83 eV, corresponding to Mn, respectively. 2+ and Mn 3 + Species. Figure 3 As can be seen from the O 1s spectrum in (d), the main peak at 529.02 eV belongs to lattice oxygen, while the peak near 530.98 eV belongs to oxygen in carbonate. Figure 3In the C 1s spectrum of (e), two characteristic peaks appear at 284.21 eV and 288.77 eV. The characteristic peak at 288.77 eV corresponds to carbon in the carbonate.

[0065] Figure 4 The image shows the EDS spectrum of the cerium-doped MnCO3-Mn2O3 composite material, from which Mn, O, C and Ce elements can be observed.

[0066] Figure 5 The image shows the elemental distribution of the cerium-doped MnCO3-Mn2O3 composite material. The signal distribution profiles of Mn and O elements highly coincide with the morphology of the cubic particles, indicating that they are uniformly distributed in the main structure. The signal of C element is slightly weaker in the region with triangular pyramidal protrusions, suggesting a local density difference of carbonate groups in this area. Ce element is uniformly distributed throughout the scanning area, but its signal intensity is significantly enhanced on the nanoparticles attached to the cubic surface, indicating that Ce has a local enrichment phenomenon in this area.

[0067] Figure 6 The infrared spectrum of the cerium-doped MnCO3-Mn2O3 composite material is located at 516.92 cm⁻¹. -1 and 675.08cm -1 The absorption peak at 723.30 cm⁻¹ is attributed to the stretching vibration of the Mn–O bond, confirming the presence of the Mn₂O₃ oxide phase. -1 and 856.39 cm -1 The spectral bands correspond to CO3. 2- The out-of-plane bending vibration and in-plane vibration, and 908.47 cm -1 The absorption peak at that point can be identified as CO3. 2- The symmetrical stretching vibrations, along with the three factors, clearly indicate the presence of the MnCO3 phase in the material.

[0068] Figure 7 The image shows the Raman spectrum of a cerium-doped MnCO3-Mn2O3 composite material. The value is located at 265.73 cm⁻¹. -1 and 310.51cm -1 The peaks at 447.98 cm⁻¹ are characteristic signals of Mn₂O₃, corresponding to the Mn–O–Mn bending vibration and the Mn–O symmetric stretching vibration, respectively. -1 The peak at this location also originates from the deformation vibration of the MnO6 octahedrons in the Mn2O3 phase. 641.46 cm⁻¹ -1 The strong peak at 866.77 cm⁻¹ corresponds to the symmetric stretching vibration of the MnO₆ octahedron. -1 The weak signal in the vicinity is attributed to CO3. 2- The vibration. 1094.86 cm -1and 1468.17cm -1 The peaks at these locations correspond to CO3. 2- Symmetric and asymmetric stretching vibrations.

[0069] Example 5

[0070] The cerium-doped MnCO3-Mn2O3 composite materials prepared in Examples 1-4 were used to prepare the positive electrode of an aqueous zinc-ion battery.

[0071] The first step is to weigh 0.24g of cerium-doped MnCO3-Mn2O3 composite material and 0.03g of acetylene black, and grind them thoroughly using an agate mortar.

[0072] The second step involves adding a binder made from a mixture of 0.03g polyvinylidene fluoride and 0.6mL of N-methylpyrrolidone to the ground product.

[0073] The third step is to coat the mixed slurry onto a stainless steel foil with a thickness of 0.01 mm and dry it at a constant temperature of 80°C for 1 hour.

[0074] The fourth step is to process the stainless steel foil into a positive electrode sheet with a diameter of 10mm after the active material is completely dried.

[0075] The fifth step involves assembling an aqueous zinc-ion battery using a zinc sheet as the negative electrode, glass fiber paper as the separator, and a mixture of 2 mol / L ZnSO4 solution and 0.2 mol / L MnSO4 solution as the electrolyte. The battery is then left to stand for 24 hours before testing.

[0076] Figure 8 This is a cycle charge-discharge diagram of an aqueous zinc-ion battery using a cerium-doped MnCO3-Mn2O3 composite material as the positive electrode. The charge-discharge test currents were set at 50 mA / g, 100 mA / g, 200 mA / g, 300 mA / g, and 500 mA / g. The composite material prepared in Example 4 showed optimal capacity retention and enhancement after activation, with a maximum reversible capacity of 304.93 mAh / g.

[0077] Figure 9 This is the cyclic voltammogram of an aqueous zinc-ion battery using a cerium-doped MnCO3-Mn2O3 composite material as the positive electrode. The figure shows that the reduction peaks of all cerium-doped samples are located around 1.26 V and 1.37 V, while the oxidation peak is around 1.64 V, indicating good cycle stability.

[0078] Figure 10The figure shows the AC impedance curves of an aqueous zinc-ion battery using a cerium-doped MnCO3-Mn2O3 composite material as the positive electrode. As can be seen from the figure, the sample prepared in Example 4 exhibits a low surface film resistance. With continuous charge and discharge cycles, the electrode gradually activates, interfacial charge transport improves, and ultimately, a stable cycle capacity is achieved.

[0079] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A cerium-doped MnCO3-Mn2O3 composite material, characterized in that: XRD diffraction peaks are at 24.5°, 31.65°, 33.14°, and 55.33°; XPS peaks are at 288.77 eV, 529.02 eV, 530.98 eV, 641.72 eV, 653.10 eV, 884.46 eV, and 916.3 eV. Cerium exhibits both +3 and +4 valences, while manganese exhibits both +2 and +3 valences.

2. The method for preparing the cerium-doped MnMnCO3-Mn2O3 composite material as described in claim 1, characterized in that, Includes the following steps: The first step is to disperse the manganese nitrate aqueous solution in pure water, then add urea and cerium nitrate hexahydrate in sequence, and stir until well mixed. The second step is to place the well-stirred solution into a hydrothermal reactor, react it at a constant temperature in an oven, and then allow it to cool down naturally. The third step is to remove the product from the hydrothermal reactor, wash and filter it, and then put it into an oven to dry. The fourth step involves calcination in a muffle furnace followed by cooling to obtain cerium-doped MnCO3-Mn2O3 composite material.

3. The method for preparing the cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the first step, the molar ratio of manganese nitrate to urea is 19:

60.

4. The method for preparing cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the first step, the molar ratio of manganese nitrate to cerium nitrate hexahydrate is 19:

1.

5. The method for preparing the cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the second step, the constant temperature reaction temperature is 160℃, and the reaction time is 6 hours.

6. The method for preparing the cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the third step, the reaction product is washed with pure water. The reaction product is placed in pure water to form a suspension, and then ultrasonicated for 3 minutes in an ultrasonic cleaner. The suspension is then filtered. The washing is repeated a total of 5 times.

7. The method for preparing cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the third step, the drying temperature is 80℃ and the drying time is 1.5 hours.

8. The method for preparing cerium-doped MnCO3-Mn2O3 composite material according to claim 2, characterized in that: In the fourth step, the calcination temperature is 450℃ and the constant temperature calcination time is 5 hours, of which: the heating program is set for 2 hours and the cooling to below 200℃ takes 2 hours.

9. The application of the cerium-doped MnCO3-Mn2O3 composite material as described in claim 1 in an aqueous zinc-ion battery.

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