A co-doped delta-manganese dioxide material, a preparation method and application thereof

Abstract

This invention provides a Co-doped δ-MnO2 material, its preparation method, and its applications, belonging to the field of new energy storage technology. This invention uses a simple one-step hydrothermal method with manganese and cobalt sources to obtain a δ-MnO2 cathode material with appropriate amounts of Co doping and oxygen vacancies, which can be achieved at 0.5 A g. ‑1 Down 655.7 mA hg ‑1 It exhibits a large specific capacitance and high rate performance with large capacity characteristics. When the current density increases to 20 A g... ‑1 Its specific capacity can still be maintained at 209.8 mA hg ‑1 This provides a high-quality candidate cathode material for building a new generation of high-performance zinc-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of new energy storage technology, and in particular to a Co-doped δ-MnO2 material, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for renewable energy, the development of efficient, safe, and low-cost electrochemical energy storage systems has become a focus of research and industry. Among numerous energy storage technologies, aqueous zinc-ion batteries have attracted considerable attention due to their unique advantages. The zinc metal anode possesses an extremely high theoretical capacity (820 mAh g⁻¹). -1 The high energy density and low redox potential (-0.76 V, relative to the standard hydrogen electrode) of aqueous electrolytes offer the potential for high energy density in the battery. Furthermore, the use of aqueous electrolytes overcomes the flammability and toxicity drawbacks of traditional organic electrolytes, while also providing the battery with excellent safety, environmental friendliness, and high ionic conductivity. In addition, the abundance and low cost of zinc resources make aqueous zinc-ion batteries a promising candidate for commercialization in applications such as large-scale grid energy storage, portable electronic devices, and smart grid support.

[0003] However, despite the excellent performance of zinc anodes, the overall performance of aqueous zinc-ion batteries largely depends on the characteristics of the cathode material. The cathode material not only provides active sites for zinc ion storage but also directly determines the battery's energy density, power density, and cycle life. Currently, the performance bottleneck of cathode materials has become a key factor limiting the large-scale application of zinc-ion batteries. Therefore, developing cathode materials with high rate / capacity, long cycle stability, and cost-effectiveness is a core challenge that urgently needs to be solved in this field.

[0004] To find ideal cathode materials, researchers have explored various candidate systems, including manganese-based oxides, vanadium-based oxides, Prussian blue analogs, layered sulfides, and organic compounds. Among these materials, manganese-based oxides, especially δ-MnO2, are considered one of the most promising species due to their low cost, environmental friendliness, high theoretical capacity, and suitable operating voltage (~1.35 V) (e.g., Chinese invention patent, application number CN202211613768.7). δ-MnO2 possesses a unique layered structure and a relatively wide interlayer spacing (approximately 7.0 Å), a structural feature that theoretically facilitates electrolyte penetration and rapid ion transport, thereby achieving rapid electron / ion conduction. However, despite these structural advantages, δ-MnO2 still faces many severe challenges in practical applications. First, its intrinsic conductivity is poor, leading to slow electron transport rates, sluggish reaction kinetics, and consequently, rapid capacity decay. Secondly, δ-MnO2 suffers from insufficient structural stability. During the repeated insertion and extraction of zinc ions, the lattice volume expands and contracts, leading to structural collapse (e.g., Chinese invention patent, application number CN202310411537.6). More importantly, Zn... 2+ As a divalent ion, Zn has a large atomic mass and extremely high charge density, characteristics that make it... 2+ When embedded in the host material, strong electrostatic interactions are generated, which greatly increases the energy barrier for ion diffusion and significantly reduces its rate performance (Advanced Energy Materials, 2021, 11, 2003994.).

[0005] To overcome these bottlenecks, researchers have proposed various modification strategies, mainly including defect engineering, pre-intercalation, and heterovalent metal ion doping (Advanced Materials, 2024, 37, 2414019. Energy StorageMaterials, 2024, 65, 103108.). While defect engineering (such as introducing oxygen vacancies) can improve the electrochemical activity of MnO2 to some extent, excessive or unstable defects often exacerbate structural changes in the material during cycling, leading to lattice distortion, particle aggregation, etc., which in turn reduces the long-term stability of the battery. Pre-intercalation technology stabilizes the layered structure by introducing metal ions or water molecules into the interlayer. However, during long-term charge and discharge, especially at low current densities, these pre-intercalated guest ions inevitably precipitate from the MnO2 interlayer and enter the electrolyte, leading to structural support failure and a rapid decrease in battery capacity.

[0006] In contrast, metal ion doping engineering is considered a more effective control method (EnergyStorage Materials, 2023, 60, 102830). This involves introducing heterogeneous metal atoms (such as Zn...). 2+ K + Ni 2+ Cu 2+、 Fe 3+ and Co 2+ Doping (e.g., by modulating the electronic structure, chemical composition, and geometry of MnO2) can effectively enhance the material's electrochemical performance. Doping not only strengthens charge / ionic conduction, narrows the electronic band gap, and promotes ion migration, but also, to some extent, suppresses the Jahn-Teller effect and improves structural stability. However, the electrochemical performance of doped oxides is actually the result of multiple coupled factors, involving the balance of ion adsorption / desorption, electron transport rate, ion diffusion barrier, and structural integrity. These complex interdependencies pose significant challenges to the rational optimization of MnO2 performance. For example, accurately determining the most suitable dopant atom type and optimal doping concentration remains a major challenge in this field.

[0007] Currently, although various doping techniques exist for modifying manganese-based cathode materials, improvements are still needed in achieving a balance between high rate / high capacity and long-cycle stability. In particular, there is a lack of clear theoretical guidance and empirical methods for precisely controlling the type and concentration of doping elements to balance material structure and electrochemical performance.

[0008] Therefore, there is an urgent need to develop a novel Co-doped δ-MnO2 cathode material to address the Zn content issue in zinc-ion batteries through rational structural design and optimization. 2+ Key issues such as slow diffusion, poor structural stability, and low conductivity have hindered the practical application of high-performance aqueous zinc-ion batteries. Summary of the Invention

[0009] The purpose of this invention is to provide a Co-doped δ-MnO2 material, its preparation method, and its application. This Co-doped δ-MnO2 material combines high rate capability, high capacity, and long cycle stability, overcoming the shortcomings of low rate capability and low capacity in manganese-doped oxide electrode materials. This is beneficial for solving the problem of Zn content in zinc-ion batteries. 2+ Key issues include slow diffusion, poor structural stability, and low conductivity.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing Co-doped δ-MnO2 materials, comprising the following steps: Manganese source, cobalt source, acid and water are mixed and subjected to hydrothermal reaction to obtain Co-doped δ-MnO2 material; The molar ratio of Co in the cobalt source to Mn in the manganese source is 0.03~0.10:1; The hydrothermal reaction is carried out at a temperature of 100~140℃ for a time of 80~120min.

[0011] Preferably, the manganese source includes at least one of potassium permanganate, manganese sulfate, manganese nitrate, and manganese chloride.

[0012] Preferably, the acid includes at least one of sulfuric acid, hydrochloric acid, nitric acid, and perchloric acid; the concentration of the acid is 0.1~2.0 mol / L.

[0013] Preferably, the molar ratio of the acid to the manganese source is 4~80:1.

[0014] Preferably, the cobalt source includes at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

[0015] Preferably, the molar ratio of Co in the cobalt source to Mn in the manganese source is 0.05:1; the concentration of the acid is 0.5 mol / L; and the hydrothermal reaction temperature is 120°C and the time is 100 min.

[0016] The present invention provides a Co-doped δ-MnO2 material prepared by the preparation method described above, which is a three-dimensional spherical structure formed by inserting two-dimensional nanosheets.

[0017] Preferably, the Co-doped δ-MnO2 material is at 0.5 A g -1 Under these conditions, the specific capacity is 655.7 mA hg. -1 ; in 20 A g -1 Under these conditions, the specific capacity is 209.8 mA hg -1 .

[0018] This invention provides the application of the Co-doped δ-MnO2 material described above as a cathode material in aqueous zinc-ion batteries.

[0019] This invention provides a method for preparing Co-doped δ-MnO2 materials. A simple one-step hydrothermal method is used with manganese and cobalt sources to obtain δ-MnO2 cathode materials with appropriate amounts of Co doping and oxygen vacancies, achieving a yield of 0.5 A g. -1 655.7 mAh g -1 It exhibits a large specific capacitance and high rate performance with large capacity characteristics. When the current density increases to 20 A g -1 Its specific capacity can still be maintained at 209.8 mA hg -1This invention provides a high-quality candidate cathode material for constructing a new generation of high-performance zinc-ion batteries. By precisely controlling the Co doping amount to 0.03~0.10, this invention achieves a synergistic improvement in the specific capacity, rate performance, and cycle stability of δ-MnO2-based cathode materials.

[0020] Compared with existing electrode materials, the Co-doped δ-MnO2 material of this invention, as a positive electrode material for zinc-ion batteries, has the following advantages: 1) This invention optimizes the charge distribution and electronic structure within the crystal by precisely controlling the Co doping concentration (the molar ratio of Co to Mn is 0.03~0.10:1), which not only effectively reduces Zn 2+ The diffusion barrier of Zn is significantly improved. 2+ Migration rate, thus giving the material excellent rate performance.

[0021] 2) The Co-doped δ-MnO2 material prepared in this invention introduces oxygen vacancies along with Co doping. These defects not only significantly modulate the band structure to improve intrinsic conductivity, but also provide Zn with... 2+ The insertion / extraction of Zn provides a rapid pathway, greatly improving reaction kinetics; furthermore, oxygen vacancy defects increase the surface energy of the system, inducing abundant electrochemical active centers and enhancing the material surface's affinity for Zn. 2+ The adsorption capacity of Co promotes the participation of more active materials in redox reactions, thereby effectively improving the specific capacity of the electrode material. Simultaneously, the synergistic effect of Co doping and oxygen vacancies effectively stabilizes the crystal structure of the material during cycling, buffers volume changes, and inhibits the structural collapse of active materials, thus significantly enhancing the cycling stability of the electrode material and helping to solve the problem of Zn in zinc-ion batteries. 2+ Key issues include slow diffusion, poor structural stability, and low conductivity. Attached Figure Description

[0022] Figure 1 The curves showing the specific capacity of δ-MnO2 prepared at different hydrothermal temperatures in Example 1 as a function of current density are shown. Figure 2 The curves showing the specific capacity of δ-MnO2 prepared under different hydrothermal times in Example 2 are as follows: Figure 3 The curves showing the specific capacity of δ-MnO2 prepared under different doping elements in Examples 3-4 are as follows: Figure 4 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x SEM images, where a is the SEM image of δ-MnO2 (120℃) in Example 1, and b is the SEM image of Co in Example 4.(M) -δ-MnO 2-x SEM photos; Figure 5 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x XRD patterns; Figure 6 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x XPS spectra of Mn 2p and Co 2p; Figure 7 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x EPR map; Figure 8 The δ-MnO2 (120℃) in Example 1 and the Co in Example 5 (L) -δ-MnO 2-x In Example 4, Co (M) -δ-MnO 2-x And Co in Example 5 (H) -δ-MnO 2-x The curve showing the specific capacity as a function of current density; Figure 9 Co in Example 4 (M) -δ-MnO 2-x Long-cycle pattern; Figure 10 Co in Example 4 (M) -δ-MnO 2-x Comparison of capacity and rate performance between the material and the Co-doped manganese dioxide prepared by the prior art in Comparative Example 1. Detailed Implementation

[0023] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0024] This invention provides a method for preparing Co-doped δ-MnO2 materials, comprising the following steps: Manganese source, cobalt source, acid and water are mixed and subjected to hydrothermal reaction to obtain Co-doped δ-MnO2 material; The molar ratio of Co in the cobalt source to Mn in the manganese source is 0.03~0.10:1; The hydrothermal reaction is carried out at a temperature of 100~140℃ for a time of 80~120min.

[0025] In this invention, the manganese source preferably includes at least one of potassium permanganate (KMnO4), manganese sulfate (MnSO4), manganese nitrate (Mn(NO3)2), and manganese chloride (MnCl4). When the manganese source is two or more of the above, this invention does not have a special limitation on the ratio of different types of manganese sources, as long as the required molar amount is reached.

[0026] In this invention, the cobalt source preferably includes at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate. When the cobalt source is two or more of the above, this invention does not have a special limitation on the ratio of different types of cobalt sources, as long as the required molar amount is achieved.

[0027] In this invention, the molar ratio of Co in the cobalt source to Mn in the manganese source is preferably 0.03~0.10:1, more preferably 0.05~0.08:1.

[0028] In this invention, the acid preferably includes at least one selected from sulfuric acid, hydrochloric acid, nitric acid, and perchloric acid; the concentration of the acid is preferably 0.1~2.0 mol / L, more preferably 0.5~1.0 mol / L. When the acid is two or more of the above-mentioned types, this invention does not have a special limitation on the ratio of different types of acids, and can be adjusted according to the dosage ratio.

[0029] In this invention, the molar ratio of acid to manganese source is preferably 4~80:1, more preferably 10~60:1, and even more preferably 20~50:1.

[0030] The present invention does not have a special limitation on the amount of water used, as long as the material is completely dissolved.

[0031] In this invention, the manganese source is added to water under magnetic stirring, followed by the addition of acid and stirring for 30 minutes to form a homogeneous solution. Then, the cobalt source is added and stirred for 15 minutes. The solution is then subjected to a hydrothermal reaction in an oven. After the oven temperature naturally drops to room temperature, the material is removed from the reactor and rinsed three times each with deionized water and anhydrous ethanol. Finally, the material is dried in an oven at 60 °C for 12 hours to obtain Co-doped δ-MnO2 material.

[0032] In this invention, the temperature of the hydrothermal reaction is preferably 100~140℃, more preferably 120~130℃, and the time is preferably 80~120min, more preferably 90~100min.

[0033] This invention, by controlling the preparation temperature and time, produces a material exhibiting a unique three-dimensional spherical structure formed by two-dimensional nanosheets, creating numerous free gaps that facilitate the free passage of ions. Simultaneously, controlling the Co doping amount avoids several problems: firstly, the formation of Co-O compounds, which is detrimental to zinc storage; secondly, increased vacancies leading to crystal structure damage; and thirdly, increased electrolyte ion adsorption strength, making ion extraction difficult during charging and resulting in poor reversibility. This invention, by controlling the preparation parameters and Co doping amount, facilitates ion entry and exit, improving the material's specific capacity and rate performance. In the Co-doped δ-MnO2 system of this invention, fluctuations in hydrothermal temperature and time within the range of 100–140℃ and 80–120 min do not significantly affect the material's structure and properties.

[0034] The present invention provides a Co-doped δ-MnO2 material prepared by the preparation method described above, which is a three-dimensional spherical structure formed by inserting two-dimensional nanosheets.

[0035] In this invention, the Co-doped δ-MnO2 material is at 0.5 A g. -1 Under these conditions, the specific capacity is 655.7 mA hg. -1 ; in 20 A g -1 Under these conditions, the specific capacity is 209.8 mA hg -1 .

[0036] This invention provides the application of the Co-doped δ-MnO2 material described above as a cathode material in an aqueous zinc-ion battery. This invention does not impose any particular limitation on the method of application; any method well-known in the art can be used.

[0037] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0039] The electrochemical performance testing methods are described in the following examples: A 2 M ZnSO4 + 0.1 M MnSO4 solution was prepared as the electrolyte solution. Then, δ-MnO2 or doped MnO2 prepared in different embodiments were used as the positive electrode of the battery, and zinc sheet was used as the negative electrode. The constant current charge-discharge (GCD) and other tests of the obtained electrode materials were carried out using Xinwei and an electrochemical workstation to obtain their capacity and rate.

[0040] Example 1 (Undoped Cobalt)

[0041] Effect of different hydrothermal temperatures on the electrochemical performance of δ-MnO2

[0042] Under magnetic stirring, 20 mg KMnO4 was added to 40 mL of deionized (DI) water; then, 5 mL of H2SO4 solution (0.5 M) was added to the above solution, and the mixture was stirred for 30 min to form a homogeneous solution. The solution was then placed in ovens at 100 °C, 120 °C and 140 °C for hydrothermal reaction for 100 min. After the oven temperature naturally dropped to room temperature, the material was removed from the reaction vessel and rinsed three times each with deionized water and anhydrous ethanol. After that, it was dried in an oven at 60 °C for 12 h to obtain δ-MnO2 prepared at different hydrothermal temperatures.

[0043] Example 2

[0044] Effect of different hydrothermal times on the electrochemical performance of δ-MnO2

[0045] 20 mg KMnO4 was added to 40 mL of deionized (DI) water under magnetic stirring. Then, 5 mL of H2SO4 solution (0.5 M) was added to the above solution, and the mixture was stirred for 30 min to form a homogeneous solution. The solution was then placed in an oven at 120 °C for hydrothermal reaction for 80 min, 100 min, and 120 min, respectively. After the oven temperature naturally dropped to room temperature, the material was removed from the reaction vessel and rinsed three times each with deionized water and anhydrous ethanol. Finally, the material was dried in an oven at 60 °C for 12 h to obtain δ-MnO2 prepared under different hydrothermal times.

[0046] Example 3

[0047] Effect of different doping elements on the electrochemical performance of δ-MnO2

[0048] 20 mg KMnO4 was added to 40 mL of deionized water under magnetic stirring. Then, 5 mL of 0.5 M H2SO4 solution was added to the above solution, and the mixture was stirred for 30 min to form a homogeneous solution. 0.0065 mmol of NH4VO3, Cr(NO3)3·9H2O, Fe(NO3)3·9H2O, NiSO4·6H2O, and Cu(NO3)3·3H2O were added to the homogeneous solution, and the mixture was stirred for 15 min. The mixture was then placed in a 120 °C oven for hydrothermal reaction for 100 min. After the oven temperature naturally cooled to room temperature, the material was removed from the reactor and rinsed three times each with deionized water and anhydrous ethanol. Finally, it was dried in a 60 °C oven for 12 h to obtain V. (M) -δ-MnO 2-x Cr (M) -δ-MnO 2-x Fe(M) -δ-MnO 2-x Ni (M) -δ-MnO 2-x and Cu (M) -δ-MnO 2-x .

[0049] Example 4

[0050] Preparation of Co-doped δ-MnO2: Under magnetic stirring, 20 mg (0.126 mmol) of KMnO4 was added to 40 mL of deionized water; then, 5 mL of H2SO4 solution (0.5 M) was added to the above solution, and the mixture was stirred for 30 min to form a homogeneous solution. 0.0065 mmol of Co(NO3)2·6H2O was added to the homogeneous solution and stirred for 15 min. The mixture was then placed in a 120 °C oven for hydrothermal reaction for 100 min. After the oven temperature naturally cooled to room temperature, the material was removed from the reaction vessel and rinsed three times each with deionized water and anhydrous ethanol. Finally, it was dried in a 60 °C oven for 12 h to obtain Co. (M) -δ-MnO 2-x .

[0051] Example 5

[0052] Using the same process as in Example 4, but changing the amount of Co(NO3)2·6H2O added to 0.0039 mmol and 0.0130 mmol respectively, Co was obtained. (L) -δ-MnO 2-x and Co (H) -δ-MnO 2-x .

[0053] Comparative Example 1

[0054] Co-doped manganese dioxide cathode materials (CoMnO-5, Co-KMnO-1 / 6, CMO) prepared by existing technologies were selected as comparisons (the existing technologies corresponding to the three materials are Chinese Journal of Power Sources, 2025, 49(7), 1303-1312. Transactions of Materials Research, 2025, 1(2), 100031. Carbon Neutralization, 2023, 2(1), 28-36.).

[0055] Characterization and performance testing

[0056] 1) Using the δ-MnO2 and zinc sheets prepared at different hydrothermal temperatures in Example 1 as the positive and negative electrodes of the battery, respectively, the specific capacity was measured as a function of current density in a 2M ZnSO4 + 0.1M MnSO4 solution. The results are shown in [Figure 1]. Figure 1 .

[0057] Figure 1 The curves showing the specific capacity of δ-MnO2 prepared at different hydrothermal temperatures in Example 1 as a function of current density are shown. Figure 1 It can be seen that the specific capacity of all samples gradually decreases with increasing current density. Among them, δ-MnO2 prepared by hydrothermal reaction at 120°C for 100 min exhibits the best rate performance and the highest capacity retention: it maintains its capacity even at low current densities (0.5 A g). -1 The initial specific capacity was the highest (255 mA hg). -1 ), and at high current density (20 A g) -1 It can still maintain the highest specific capacity (20 mA hg) -1 The results show that the material prepared at 100°C and 140°C is significantly superior to the material prepared at 100°C and 140°C.

[0058] 2) Using the δ-MnO2 and zinc sheets prepared under different hydrothermal times in Example 2 as the positive and negative electrodes of the battery, respectively, their specific capacity was measured as a function of current density in a 2 M ZnSO4 + 0.1 M MnSO4 solution. The results are shown in [Figure 1]. Figure 2 .

[0059] Figure 2 The curves showing the specific capacity of δ-MnO2 prepared under different hydrothermal times as a function of current density in Example 2 are shown. Figure 2 It can be seen that δ-MnO2 prepared by hydrothermal reaction at 120°C for 100 min exhibits the best rate performance and the highest capacity retention: it maintains its capacity even at low current densities (0.5 A g). -1 The initial specific capacity was the highest (255 mA hg). -1 ), and at high current density (20 A g) -1 It can still maintain the highest specific capacity (20 mA hg) -1 The results showed that the material prepared by hydrothermal reaction at 80 min and 120 min was significantly superior to the material prepared by hydrothermal reaction.

[0060] 3) Using δ-MnO2 and zinc sheets prepared with different element doping in Examples 3-4 as the positive and negative electrodes of the battery, respectively, their specific capacity was measured as a function of current density in a 2M ZnSO4 + 0.1M MnSO4 solution. The results are shown in [Figure 1]. Figure 3 .

[0061] Figure 3The curves showing the specific capacity of δ-MnO2 prepared under different doping elements in Examples 3-4 are given as curves showing the change with current density. Figure 3 It is evident that doping with different metal elements significantly affects the rate performance of δ-MnO2. With increasing current density, the specific capacity of all doped samples gradually decreases, but the degree of decrease varies depending on the doping element. Among them, Co-doped δ-MnO2 (Co... (M) -δ-MnO 2-x It exhibits the best rate performance: at a low current density of 0.5 A g -1 It has a high initial specific capacity (655.7 mA hg). -1 Furthermore, it exhibits the slowest capacity decay at high current densities, reaching 20 A g. -1 Maintain 209.8 mA hg -1 The specific capacity value.

[0062] 4) Figure 4 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x SEM images, where a is the SEM image of δ-MnO2 (120℃) in Example 1, and b is the SEM image of Co in Example 4. (M) -δ-MnO 2-x SEM images; by Figure 4 It can be seen that δ-MnO2 exhibits an irregular flower-like structure, and Co... (M) -δ-MnO 2-x It still exhibits a flower-like shape with stacked nanosheets, indicating that the morphology was not destroyed during the metal doping process.

[0063] 5) Figure 5 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x XRD patterns; by Figure 5 It can be seen that the diffraction peaks of all samples are in good agreement with the characteristic peaks of the δ-MnO2 standard card (JCPDS# 80-1098), indicating that the synthesized materials are all pure phase δ-MnO2 and Co doping has not changed the layered crystal structure of δ-MnO2.

[0064] 6) Figure 6 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x XPS spectra of Mn 2p and Co 2p; by Figure 6 It can be seen that δ-MnO2 and Co (M) -δ-MnO 2-xThe Mn 2p spectra all exhibit two characteristic peaks, attributed to Mn 2p 3 / 2 and Mn 2p 1 / 2 respectively, indicating that Mn mainly exists as Mn2. 4+ and Mn 3+ Mixed valence states exist. Compared to the undoped sample, the Mn 2p peak position shifts slightly after Co doping, and Mn... 3+ / Mn 4+ The change in proportion indicates that Co doping affected the chemical environment of Mn. The Co 2p XPS spectra show distinct Co 2p 3 / 2 and Co 2p 1 / 2 characteristic peaks near the binding energies of 782.7 eV and 797.2 eV, respectively, confirming the successful incorporation of Co into the δ-MnO2 lattice.

[0065] 7) Figure 7 The δ-MnO2 (120℃) in Example 1 and the Co in Example 4 (M) -δ-MnO 2-x EPR map; by Figure 7 It can be seen that Co (M) -δ-MnO 2-x The characteristic peak (g = 2.0) of the Mn-O bond in the medium is significantly stronger than that of δ-MnO2, indicating that Co partially replaces the Mn sites and introduces oxygen vacancies to maintain the charge balance of the material. This means a better electronic structure, more electroactive sites and faster ion transport.

[0066] 8) Test the effect of different Co doping amounts on the electrochemical performance of δ-MnO2: Using δ-MnO2 (120℃) in Example 1 and Co in Example 5 respectively (L) -δ-MnO 2-x In Example 4, Co (M) -δ-MnO 2-x In Example 5, Co (H) -δ-MnO 2-x Using zinc sheet as the positive electrode and zinc sheet as the negative electrode in a 2M ZnSO4 + 0.1M MnSO4 solution, the specific capacity was measured as a function of current density. The results are shown in [Figure number missing]. Figure 8 .from Figure 8 It can be seen from this that at a low current density of 0.5Ag -1 At this point, the specific capacity of undoped Co-containing δ-MnO2 is only about 270 mAh g. -1 Co (H) -δ-MnO 2-x Increased to approximately 310 mAhg -1 Co (L) -δ-MnO 2-x Although it reached approximately 440 mAhg -1The initial specific capacity, but the performance advantage did not last, Co (M) -δ-MnO 2-x Achieve 655.7mAh g -1 The ultra-high specific capacity; as the current density gradually increases to 2.0, 5.0, and 10.0 Ag... -1 The specific capacity of δ-MnO2 rapidly decreased to 100 mAhg. -1 Within, Co (L) -δ-MnO 2-x The specific capacity dropped to approximately 200 mAhg -1 And Co (M) -δ-MnO 2-x It can still maintain 280 mAhg -1 The above specific capacitance; when the current density increases to 20.0 A g - ¹At high rates, the specific capacity of δ-MnO2 is close to 0 mAhg. -1 Co (L) -δ-MnO 2-x The specific capacity decays rapidly, Co (H) -δ-MnO 2-x Only about 90 mAhg remains -1 And Co (M) -δ-MnO 2-x The specific capacity remains stable at 209.8 mAhg. -1 This indicates that the electrode material possesses excellent rate performance. In this invention, the Co doping amount ranges from Co... (L) To Co (H) That is, the molar ratio of Co to Mn is 0.03~0.10, where Co (M) The doping amount (molar ratio 0.05) yields the best overall performance.

[0067] 9) Figure 9 Co in Example 4 (M) -δ-MnO 2-x Long-cycle graph; by Figure 9 It can be seen that in 5 Ag -1 After 3500 cycles, its capacity remains at approximately 100% of its initial capacity, indicating that Co... (M) -δ-MnO 2-x It exhibits excellent cycle stability.

[0068] 10) Electrochemical performance tests were conducted using the Co-doped manganese dioxide cathode material from Comparative Example 1 as the cathode and a zinc sheet as the anode, comparing it with the Co-doped manganese dioxide cathode material from Example 4 of this invention. (x) -δ-MnO 2-x A comparison was made using (0.03≤x≤0.10, with x=0.05 being the preferred value), and the results are as follows. Figure 10 As shown.

[0069] Figure 10 Co in Example 4 (M) -δ-MnO 2-x The comparison chart shows the capacity and rate performance of the Co-doped manganese dioxide prepared by the prior art in Comparative Example 1. The comparison results confirm that the Co-doped manganese dioxide in Example 4 of this invention... (M) -δ-MnO 2-x The material differs from existing Co-doped manganese dioxide in its structural design and has achieved a breakthrough improvement in electrochemical performance, giving it significant advantages.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing Co-doped δ-MnO2 material, characterized in that, Includes the following steps: Manganese source, cobalt source, acid and water are mixed and subjected to hydrothermal reaction to obtain Co-doped δ-MnO2 material; The molar ratio of Co in the cobalt source to Mn in the manganese source is 0.03~0.10:1; The hydrothermal reaction is carried out at a temperature of 100~140℃ for a time of 80~120min.

2. The preparation method according to claim 1, characterized in that, The manganese source includes at least one of potassium permanganate, manganese sulfate, manganese nitrate, and manganese chloride.

3. The preparation method according to claim 1, characterized in that, The acid includes at least one of sulfuric acid, hydrochloric acid, nitric acid, and perchloric acid; the concentration of the acid is 0.1~2.0 mol / L.

4. The preparation method according to claim 2 or 3, characterized in that, The molar ratio of the acid to the manganese source is 4~80:

1.

5. The preparation method according to claim 1, characterized in that, The cobalt source includes at least one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

6. The preparation method according to claim 2 or 5, characterized in that, The molar ratio of Co in the cobalt source to Mn in the manganese source is 0.05:1; the concentration of the acid is 0.5 mol / L; the hydrothermal reaction temperature is 120℃ and the time is 100 min.

7. The Co-doped δ-MnO2 material prepared by the preparation method according to any one of claims 1 to 6, characterized in that, A three-dimensional spherical structure is formed by inserting two-dimensional nanosheets.

8. The Co-doped δ-MnO2 material according to claim 7, characterized in that, The Co-doped δ-MnO2 material, at 0.5 A g -1 Under these conditions, the specific capacity is 655.7 mA hg. -1 ; in 20 A g -1 Under these conditions, the specific capacity is 209.8 mA hg -1 .

9. The application of the Co-doped δ-MnO2 material as a cathode material in an aqueous zinc-ion battery according to claim 7 or 8.

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