A Co-doped α-MnO2 material, its preparation method, and its application in anode materials
By preparing Co-doped α-MnO2 materials via a hydrothermal method, the problems of poor conductivity and poor cycle stability of α-MnO2 anode materials were solved, achieving high specific capacity and excellent rate performance at low current density, thus extending battery life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI UNIV OF SCI & TECH
- Filing Date
- 2026-03-19
- Publication Date
- 2026-06-09
AI Technical Summary
Existing α-MnO2 anode materials suffer from poor conductivity, unsatisfactory cycle stability, and difficulty in achieving high specific capacity at low current densities.
Co-doped α-MnO2 materials were prepared by a hydrothermal method. By oxidizing Co2+ to Co3+ in an acidic environment and replacing the octahedral lattice sites of Mn4+, uniform doping was formed. Combined with the nanorod morphology, the structural stability and conductivity of the material were improved.
It significantly improves the discharge specific capacity and rate performance of the material, extends the cycle life, and exhibits high reversible capacity and good cycle stability.
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Figure CN122166839A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery electrode material technology, specifically relating to a Co-doped α-MnO2 material, its preparation method, and its application in negative electrode materials. Background Technology
[0002] Manganese dioxide (MnO2) is widely regarded as a promising anode material for lithium-ion batteries due to its high theoretical specific capacity (approximately 1232 mAh / g), abundant resources, environmental friendliness, and low cost. Its electrochemical performance is profoundly dependent on its crystal structure: among various crystal forms, α-MnO2 possesses a unique [2×2] and [1×1] tunnel-interleaved structure. The larger tunnel space provides an ideal channel for the rapid insertion / extraction of lithium ions, giving it greater potential in rate performance compared to crystal forms such as β-MnO2.
[0003] However, the practical application of MnO2 is limited by two key bottlenecks: First, its intrinsic electronic conductivity is low, which restricts the full utilization of the active material and the capacity release at high rates; second, during the repeated insertion and extraction of lithium ions, Mn... 3+ The Jahn-Teller effect can induce severe lattice distortion and structural stress accumulation, leading to electrode material pulverization, rapid capacity decay, and deterioration of cycling stability. To address these challenges, researchers have attempted techniques including nanomorphic manipulation (DOI:10.1016 / J.IJOES.2025.101003); (DOI: 10.1039 / d4ma00880d) and composite structure construction (DOI:10.1016 / J.JELECHEM.2025.119336); (DOI: 10.1016 / j.jcis.2023.06.003 Various strategies have been employed, including elemental doping (DOI:10.1016 / j.ceramint.2018.07.108); (DOI:10.1016 / j.jallcom.2021.161772). For example, α-MnO2 with different morphologies (such as urchin-like, needle-like, and fibrous) can be prepared by hydrothermal methods. Among them, fibrous α-MnO2 with high oxygen vacancy concentration can achieve a capacity of 315 mAh / g after 60 cycles at a current of 100 mA / g (DOI:10.1016 / J.IJOES.2025.101003). Studies have also shown that in-situ growth methods can be used to prepare α-MnO2@NiCoMOF composites, which improve the initial coulombic efficiency by about 20% and exhibit better capacity retention at different rate expansions. However, the above methods mostly focus on surface engineering or physical compositing, and are difficult to fundamentally control the evolution of bulk structure dominated by the Jahn-Teller effect.
[0004] In contrast, elemental doping—especially cation doping—is considered an effective way to control the intrinsic electrical properties and structural stability of materials at the atomic scale. Dopant ions can enter the MnO2 lattice, improving conductivity by altering the local electronic structure and enhancing lattice stability through bonding. Among many doping elements, cobalt (Co) exhibits unique advantages due to its similar ionic radius to manganese (Mn) and its rich valence state characteristics. Theoretical studies have shown that Co doping is expected to alleviate Jahn-Teller distortion by adjusting the valence state distribution of Mn and introducing beneficial lattice strain, thereby simultaneously improving the structural stability and lithium-ion diffusion kinetics of the material. Nevertheless, how to achieve effective Co doping through a simple and controllable synthesis process, so as to fully unleash the high capacity potential of MnO2 at low current densities while maintaining good rate performance, remains a pressing technical challenge. Summary of the Invention
[0005] To overcome the problems of poor conductivity, poor cycle stability, and difficulty in achieving high specific capacity at low current densities in existing α-MnO2 anode materials, the present invention aims to provide a Co-doped α-MnO2 material, its preparation method, and its application in anode materials. This method is simple and environmentally friendly, and the prepared material has the characteristics of uniform composition and regular morphology, exhibiting significantly improved discharge specific capacity and excellent rate performance at low current densities.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing Co-doped α-MnO2 material includes the following steps; Step 1: Dissolve potassium permanganate (KMnO4) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) in deionized water, stir and mix to obtain a homogeneous precursor solution; Step 2: Add hydrochloric acid solution dropwise to the precursor solution and stir continuously to ensure thorough mixing; Step 3: Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction; Step 4: After the reaction is complete, the product is centrifuged, washed, and dried to obtain Co-doped α-MnO2 material.
[0007] In step 1, potassium permanganate (KMnO4) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) are dissolved in deionized water, wherein the concentration of the KMnO4 aqueous solution is 0.03-0.06 mol / L. The lower potassium ion concentration is beneficial to the formation and stability of α-MnO2. The molar ratio of (Co(NO3)2·6H2O) to KMnO4 is 0.1~2%, because moderate doping can balance the contradiction between improved conductivity and ion diffusion rate, while excessive doping will lead to deterioration of kinetic performance due to excessive lattice contraction. The mixed solution is stirred on a magnetic stirrer for 40~50 min to ensure uniform mixing of the reaction precursors.
[0008] In step 2, the concentration of hydrochloric acid added is 1.5~2.5 mol / L, and the volume ratio of its added amount to the precursor solution is 1:(14~16). This acidity condition not only ensures the formation of pure-phase α-MnO2, but also synergistically induces the formation of nanorod-like morphology and moderate crystal defects that are beneficial to electrochemical performance, laying the foundation for subsequent Co doping to improve the structural stability and conductivity of the material.
[0009] In step 3, the hydrothermal reaction temperature is 100~200℃, the reaction time is 18~20 hours, and the volume of the reaction solution occupies 70% of the reactor volume. This results in an α-MnO2 anode material that possesses high structural stability, high electronic / ionic conductivity, and high reversible capacity: Co doping stabilizes the crystal lattice, suppresses cycle volume expansion, and extends cycle life; simultaneously, it improves the electronic structure, and combined with the short-range diffusion of the nano-morphology, enhances rate performance; while the perfect crystallinity and defect synergy promote the reversible redox reaction, thereby improving the initial coulombic efficiency and reversible capacity.
[0010] In step 4, the centrifugal washing involves first centrifuging and washing several times with deionized water, then centrifuging and washing several times with anhydrous ethanol. The drying temperature is 70~90℃, and the drying time is 18~20 hours.
[0011] The Co-doped α-MnO2 is used as the negative electrode of a lithium-ion battery.
[0012] The obtained Co-doped α-MnO2 products are uniformly sized and well-grown nanorods. The nanorods have a diameter of approximately 20–30 nm and a length distribution ranging from 0.15–0.19 μm. Notably, some of the rods exhibit a hollow structure. This unique morphology helps increase the contact area with the electrolyte and provides more active sites, thereby further enhancing the electrochemical performance of the material.
[0013] The beneficial effects of this invention are: This invention utilizes a hydrothermal method to prepare Co-doped α-MnO2. The process is simple and low-cost, and the prepared product has high purity, good crystal form, and good dispersibility. As an electrode material, it exhibits high rate performance and cycle stability.
[0014] This invention selects Co 2+Co-doped α-MnO2 was synthesized via a hydrothermal method as a dopant ion. This nanorod-shaped material has a large specific surface area, increasing the contact area for the reaction and thus improving electrochemical performance. Electrochemical performance tests showed that the material prepared by this method, as a negative electrode material for lithium-ion batteries, exhibits high specific capacity and good rate performance at low current densities.
[0015] This invention employs a hydrothermal method to convert Co in an acidic environment. 2+ +Oxidation to Co 3+ And successfully replaced Mn 4+ The octahedral lattice sites of Co are used to achieve uniform doping, which is simple, low-cost, and produces products with high purity, well-formed crystals, and excellent dispersibility. The introduction of Co induces oxygen vacancies and lattice defects in the MnO2 lattice and optimizes the d-electron configuration of Mn sites, promoting d-electron delocalization and increasing eg orbital occupancy, thereby effectively reducing the band gap and improving intrinsic conductivity. The resulting material is a three-dimensional structure assembled from nanorods, with a large specific surface area, which significantly increases the electrode / electrolyte contact area. At the same time, Co doping further stabilizes the tunnel structure of α-MnO2, suppresses volume expansion during cycling, and the improved electronic conductivity, combined with the short-range diffusion path provided by the nanomorphology, significantly enhances charge transfer kinetics. Electrochemical test results show that this material, as a lithium-ion battery anode, exhibits high specific capacity at low current densities and also has excellent rate performance and cycle stability. Attached Figure Description
[0016] Figure 1 This is the XRD pattern of the product prepared in this invention.
[0017] Figure 2 This is an SEM image of the product of this invention.
[0018] Figure 3 This is the EDS energy spectrum of the product of this invention.
[0019] Figure 4 These are the rate performance test results of the product of this invention under different current densities.
[0020] Figure 5 This is a cycling curve of the product of this invention at a current density of 200 mA / g. Detailed Implementation
[0021] The present invention will now be described in further detail with reference to the accompanying drawings.
[0022] Example 1 The method for preparing Co-doped α-MnO2 includes the following steps: Step 1: Weigh 0.379 g KMnO4 and 0.0034 g (Co(NO3)2·6H2O), add deionized water to a final volume of 35 mL, and stir on a magnetic stirrer for 40 min to prepare a mixed solution.
[0023] Step 2: Add 2.5 mL of 2 mol / L hydrochloric acid to the mixed solution and stir until homogeneous.
[0024] Step 3: Transfer the solution from Step 2 into a 50 mL polytetrafluoroethylene-lined high-pressure reactor and keep it at 180 °C for 18 h.
[0025] Step 4: After the reaction is complete, the product is poured into a centrifuge tube and placed in a centrifuge. It is centrifuged three times with deionized water and three times with anhydrous ethanol. Finally, it is dried at 80 °C for 12 h to obtain Co-doped α-MnO2 nanoparticles.
[0026] Example 2 The method for preparing Co-doped α-MnO2 includes the following steps: Step 1: Weigh 0.379 g KMnO4 and 0.0037 g (Co(NO3)2·6H2O), add deionized water to a final volume of 35 mL, and stir on a magnetic stirrer for 45 min to prepare a mixed solution.
[0027] Step 2: Add 2.2 mL of 2 mol / L hydrochloric acid to the mixed solution and stir until homogeneous.
[0028] Step 3: Transfer the solution from Step 2 into a 50 mL polytetrafluoroethylene-lined high-pressure reactor and keep it at 150 °C for 19 h.
[0029] Step 4: After the reaction is complete, the product is poured into a centrifuge tube and placed in a centrifuge. It is centrifuged three times with deionized water and three times with anhydrous ethanol. Finally, it is dried at 80 °C for 14 h to obtain Co-doped α-MnO2 nanoparticles.
[0030] Example 3 The method for preparing Co-doped α-MnO2 includes the following steps: Step 1: Weigh 0.379 g KMnO4 and 0.0039 g (Co(NO3)2·6H2O), add deionized water to a final volume of 35 mL, and stir on a magnetic stirrer for 50 min to prepare a mixed solution.
[0031] Step 2: Add 2.3 mL of 2 mol / L hydrochloric acid to the mixed solution and stir until homogeneous.
[0032] Step 3: Transfer the solution from Step 2 into a 50 mL polytetrafluoroethylene-lined high-pressure reactor and keep it at 170 °C for 20 h.
[0033] Step 4: After the reaction is complete, the product is poured into a centrifuge tube and placed in a centrifuge. It is centrifuged 3 times with deionized water and then 3 times with anhydrous ethanol. Finally, it is dried at 80 °C for 16 h to obtain Co-doped α-MnO2 nanoparticles.
[0034] Example 4 The method for preparing Co-doped α-MnO2 includes the following steps: Step 1: Weigh 0.379 g KMnO4 and 0.0040 g (Co(NO3)2·6H2O), add deionized water to a final volume of 35 mL, and stir on a magnetic stirrer for 45 min to prepare a mixed solution.
[0035] Step 2: Add 2.4 mL of 2 mol / L hydrochloric acid to the mixed solution and stir until homogeneous.
[0036] Step 3: Transfer the solution from Step 2 into a 50 mL polytetrafluoroethylene-lined high-pressure reactor and keep it at 180 °C for 18 h.
[0037] Step 4: After the reaction is complete, the product is poured into a centrifuge tube and placed in a centrifuge. It is centrifuged three times with deionized water and three times with anhydrous ethanol. Finally, it is dried at 80 °C for 24 h to obtain Co-doped α-MnO2 nanoparticles.
[0038] like Figure 1 As shown, the diffraction peaks of Co-doped α-MnO2 at 12.7°, 18.1°, 28.8°, 37.5°, 41.9°, 49.8°, 56.3°, 60.2°, 65.1°, 69.7°, and 72.7° correspond to the (110), (200), (310), (211), (301), (411), (600), (521), (002), (541), and (312) crystal planes, respectively. This result is consistent with the standard card library JCPDS (NO.44-0141, a=9.815 Å, b=9.815 Å, c=2.847 Å) corresponding to space group I 4 / m (87). The sharp and clear diffraction peaks indicate that the prepared sample has good crystallinity, and no other impurity diffraction peaks were found, indicating that Co was successfully incorporated into the α-MnO2 lattice.
[0039] like Figure 2As shown, the Co-doped α-MnO2 prepared based on Example 1 exhibits a typical nanorod morphology, indicating that Co doping did not alter the macroscopic morphology of the material, and the sample maintained a stable and consistent growth habit during hydrothermal processing. SEM images at different magnifications show that the nanorods are densely distributed, have a regular morphology, and exhibit no obvious agglomeration or degradation, indicating that doping did not significantly damage the material structure. The average particle size of the sample is approximately 0.17 μm, which is beneficial for increasing the electrochemical reaction contact area, thereby improving electrochemical performance.
[0040] like Figure 3 As shown in the EDS spectrum, the four elements K, Mn, O, and Co are clearly present in the Co-doped α-MnO2 lattice sample, and each element exhibits a uniform spatial distribution at the microscale. This proves that Co ions are successfully embedded in the α-MnO2 lattice, rather than existing as an independent cobalt oxide impurity phase. The formation of this uniform doped structure is attributed to the synergistic control of the preparation process: in step 1 of Example 1, the reactants are precisely metered and thoroughly stirred to allow Mn... 7+ With Co 2+ The mixture is homogeneously mixed at the molecular level; in step 2, hydrochloric acid is added dropwise to provide an acidic environment and participate in the redox reaction, promoting the oxidation of Mn. 7+ To Mn 4+ Reduction, on the other hand, to prevent Co 2+ Premature hydrolysis precipitation ensures the coexistence of the two metal ions in the liquid phase; based on this, the hydrothermal crystallization in step 3 is carried out at 180℃ and autogenous pressure, Mn 4+ Gradually, an α-MnO2 tetragonal lattice is formed, while Co in the solution... 2+ It is oxidized to Co in an acidic oxidizing environment. 3+ and in situ replace Mn 4+ Octahedral sites are used to achieve uniform doping at the lattice scale, K + The template ions stabilize the tunnel structure and maintain the integrity of the crystal form. The centrifugal washing in step 4 removes unreacted or surface-adsorbed free ions, so that the Co signal detected at the end is entirely from the inside of the crystal lattice rather than the surface residue. This results in a uniform distribution of the four elements in the EDS characterization. This microstructure feature provides strong support for the successful doping of Co into the α-MnO2 crystal lattice and also confirms the rationality and effectiveness of the preparation method.
[0041] like Figure 4 As shown, the Co-doped α-MnO2 material prepared in Example 1 exhibits high discharge capacity at different current densities. Even at a high current density of 2 A / g, its discharge capacity remains at 243.3 mAh / g; when the current density is restored to 100 mA / g, the discharge capacity can be restored to 622.2 mAh / g, demonstrating excellent reversibility and rate performance.
[0042] like Figure 5 As shown, the Co-doped α-MnO2 material prepared in Example 1 underwent cycling performance testing at a current density of 200 mA / g. The specific capacity decreased in the initial cycles, reaching a minimum of 483.9 mAh / g at the 31st cycle; subsequently, the capacity gradually recovered, reaching 1109.8 mAh / g at the 200th cycle. The coulombic efficiency remained high throughout the cycling process, stabilizing at approximately 98.53% after 200 cycles. These results indicate that Co doping significantly improves the cycling stability and capacity retention of the α-MnO2 anode material, effectively extending the battery's cycle life.
Claims
1. A method for preparing Co-doped α-MnO2 material, characterized in that, Includes the following steps; Step 1: Dissolve potassium permanganate (KMnO4) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) in deionized water, stir and mix to obtain a homogeneous precursor solution; Step 2: Add hydrochloric acid solution dropwise to the precursor solution and stir continuously to ensure thorough mixing; Step 3: Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction; Step 4: After the reaction is complete, the product is centrifuged, washed, and dried to obtain Co-doped α-MnO2 material.
2. The method for preparing Co-doped α-MnO2 material according to claim 1, characterized in that, In step 1, potassium permanganate (KMnO4) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) are dissolved in deionized water, wherein the concentration of the KMnO4 aqueous solution is 0.03-0.06 mol / L.
3. The method for preparing Co-doped α-MnO2 material according to claim 2, characterized in that, The molar ratio of (Co(NO3)2·6H2O) to KMnO4 is 0.1~2%, and the mixed solution is stirred on a magnetic stirrer for 40~50 min.
4. The method for preparing Co-doped α-MnO2 material according to claim 1, characterized in that, In step 2, the concentration of hydrochloric acid added is 1.5~2.5 mol / L, and the volume ratio of the added amount to the precursor solution is 1:(14~16).
5. The method for preparing Co-doped α-MnO2 material according to claim 1, characterized in that, In step 3, the hydrothermal reaction temperature is 100~200℃, the reaction time is 18~20 hours, and the volume of the reaction solution accounts for 70% of the volume of the reaction vessel.
6. The method for preparing Co-doped α-MnO2 material according to claim 1, characterized in that, In step 4, the centrifugal washing involves first centrifuging and washing several times with deionized water, then centrifuging and washing several times with anhydrous ethanol. The drying temperature is 70~90℃, and the drying time is 18~20 hours.
7. The application of the Co-doped α-MnO2 material prepared by the method according to any one of claims 1-6, characterized in that, The Co-doped α-MnO2 is used as the negative electrode of a lithium-ion battery.
8. A Co-doped α-MnO2 material prepared by the method according to any one of claims 1-6, characterized in that, The Co-doped α-MnO2 is a uniformly sized and well-grown nanorod; the nanorod diameter is 20~30 nm and the length distribution ranges from 0.15 to 0.19 μm; some of the rods exhibit a hollow structure.