A metallic regulation type Mn-doped spinel ZnCo2O4 negative electrode material and a preparation method thereof

Abstract

This invention discloses a metallically modulated Mn-doped spinel-type ZnCo₂O₄ anode material and its preparation method, belonging to the field of lithium-ion battery electrode materials. The material maintains a pure-phase spinel crystal structure, exhibiting uniform and regular 2–5 μm polyhedral micron-sized particles with layered wrinkles and stepped porous structures on the surface. Mn and Co exist in mixed valence states of Mn²⁺ / Mn³⁺ and Co²⁺ / Co³⁺. First-principles DFT calculations confirm that Mn doping transforms the material from a semiconductor to a metallic conductor, eliminating the band gap, significantly increasing the Fermi level electronic state density, and reducing the lithium-ion diffusion barrier from 1.05 eV to 0.75 eV. Its preparation employs a hydrothermal method combined with a calcination process. This material exhibits high reversible specific capacity at a current density of 0.1 A·g⁻¹, excellent capacity retention after 200 cycles, outstanding rate performance in the range of 0.1~1.0 A·g⁻¹, significantly reduced charge transfer resistance, and overall electrochemical performance far superior to pure-phase ZnCo₂O₄. It can be directly used as a negative electrode for lithium-ion batteries and has good application prospects in the field of lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrode material technology, specifically relating to a Mn-doped spinel-type ZnCo2O4 anode material, a method for microstructure control, and the application of this material in lithium-ion batteries. Background Technology

[0002] Spinel-type ZnCo2O4 possesses high theoretical capacity and a stable crystal structure, making it a highly promising anode material for lithium-ion batteries. However, its intrinsic conductivity is poor, its charge-discharge volume expansion is large, and it is prone to structural collapse during cycling, leading to rapid capacity decay. Mn doping can tune the crystal structure and electronic states, improving conductivity and ion transport efficiency; however, the related structure-property relationships and mechanisms are not yet systematically studied. Summary of the Invention

[0003] 1. Materials Design

[0004] The Mn-doped spinel-type ZnCo2O4 material designed in this invention retains the pure-phase spinel structure, with significantly improved crystallinity and morphological order. It exhibits uniform and regular polyhedral micron-sized particles with a size concentrated in 2–5 μm and a dense layered fold and stepped structure on the surface. Mn, Zn, and Co exist in mixed valence states of Mn²⁺ / Mn³⁺, Zn²⁺, and Co²⁺ / Co³⁺, respectively. Mn doping transforms the material from a semiconductor to a metallic material, the band gap disappears, and the electronic state density at the Fermi level is greatly increased. The lithium-ion diffusion barrier is reduced from 1.05 eV to 0.75 eV, and the electron transport and ion diffusion kinetics are significantly enhanced.

[0005] 2. Preparation method

[0006] Hydrothermal synthesis: Using distilled water as solvent, manganese acetate, zinc acetate, cobalt acetate and urea are added according to the ratio and stirred until completely dissolved to obtain a homogeneous precursor solution; the foamed nickel, which has been ultrasonically cleaned with hydrochloric acid, deionized water and anhydrous ethanol, is placed in a hydrothermal reactor, the precursor solution is added, and the hydrothermal reaction is carried out at 160℃ for 10 hours to obtain the carbonate precursor.

[0007] Calcination process: The precursor was washed with distilled water and anhydrous ethanol and thoroughly dried at 60℃; the temperature was increased to 350℃ at a rate of 2℃ / min, and calcined in air for 5 hours to complete the calcination. It was then naturally cooled to room temperature to obtain Mn-doped spinel-type ZnCo2O4 anode material.

[0008] 3. Performance advantages

[0009] Capacity and Cycling Performance: At a current density of 0.1 A·g⁻¹, the reversible specific capacity is significantly improved, the capacity retention rate is excellent after 200 cycles, the coulombic efficiency is stable over a long period of time, and the overall performance is far superior to pure phase ZnCo2O4.

[0010] Rate performance: It exhibits excellent capacity output capability in a wide current density range of 0.1~1.0A・g⁻¹, and the capacity can be quickly recovered after high current discharge, with good high rate adaptability.

[0011] Kinetic characteristics: The charge transfer resistance is significantly reduced, the lithium ion diffusion coefficient is greatly improved, and the electrode reaction is jointly dominated by diffusion control and surface pseudocapacitance control, with pseudocapacitance contributing a high proportion. The ion transport and charge transfer kinetics are synergistically enhanced. Attached Figure Description

[0012] Figure 1 These are the XRD patterns of pure ZnCo2O4 and Mn0.5Zn0.5Co2O4, used to characterize their crystal structure and crystallinity.

[0013] Figure 2 These are SEM images of Mn0.5Zn0.5Co2O4 and pure ZnCo2O4, used to observe the microstructure and particle size.

[0014] Figure 3 These are SAED, TEM, and EDS elemental distribution maps of Mn0.5Zn0.5Co2O4, used to analyze crystal orientation, microstructure, and elemental distribution uniformity.

[0015] Figure 4 These are the XPS full spectrum and high-resolution spectrum of Mn0.5Zn0.5Co2O4, used to characterize the elemental valence state and surface chemical composition.

[0016] Figure 5 These are the CV curves, charge-discharge curves, cycle performance and rate performance graphs of the two materials, used to evaluate the electrochemical lithium storage performance and cycle stability.

[0017] Figure 6 It includes CV curves, peak current fitting, EIS spectra, and lithium-ion diffusion coefficient calculations at different scan rates, used to analyze electrode kinetics and ion transport characteristics.

[0018] Figure 7 These are band structure, total density of states, and partial density of states diagrams for two materials, used to reveal the evolution of electronic structure and conduction mechanism.

[0019] Figure 8 These are the work functions, electron transfer diagrams, and lithium-ion adsorption energy diagrams of the two materials, used to explain the interfacial charge transfer and lithium-ion adsorption behavior.

[0020] Figure 9 These are lithium-ion diffusion energy barriers and differential charge density diagrams for two materials, used to elucidate lithium-ion diffusion kinetics and charge distribution patterns. Detailed Implementation

[0021] Implementation 1: Material Preparation

[0022] A 4 cm² piece of nickel foam was immersed in a 2.5 mol / L HCl solution for 30 minutes, ultrasonically cleaned with deionized water, and then dried. 0.2 g PVP, 0.5 mmol manganese acetate tetrahydrate, 0.5 mmol zinc acetate dihydrate, 2 mmol cobalt acetate tetrahydrate, and 3.0 mmol urea were dissolved in 60 mL distilled water and magnetically stirred for 1.5 hours. The mixture was transferred to a polytetrafluoroethylene autoclave and hydrothermally reacted at 160 °C for 10 hours to obtain the precursor. The precursor was then annealed in air at a rate of 2 °C / min to 350 °C for 5 hours to obtain Mn0.5Zn0.5Co2O4 material.

[0023] Implementation 2: Performance Verification

[0024] XRD patterns show characteristic peaks of pure-phase spinel-type ZnCo2O4 with no impurities, and the crystallinity of the Mn-doped sample is significantly improved. XPS analysis shows that Mn exists in a mixed valence state of Mn²⁺ / Mn³⁺, Zn is in the +2 valence state, and Co is in a mixed valence state of Co²⁺ / Co³⁺. SEM shows that the material is a uniform and regular polyhedral particle with a size of 2–5 μm and a layered wrinkle and step structure on the surface. Electrochemical tests show that the initial discharge capacity is significantly improved in the voltage range of 0.01–3.0 V and the current density of 0.1 A·g⁻¹, the capacity retention is excellent after 200 cycles, the charge transfer resistance is reduced, and the lithium-ion diffusion coefficient is improved.

[0025] Implementation 3: DFT Theoretical Calculation

[0026] Supercell models of pure-phase ZnCo2O4 and Mn0.5Zn0.5Co2O4 were constructed, and first-principles calculations were performed using VASP software. The exchange-correlation functional was PBE, with a cutoff energy of 400 eV and a k-point grid of 3×3×1. The band structure, density of states, differential charge density, and lithium-ion diffusion barrier were calculated. The results show that Mn doping eliminates the band gap, increases the electronic density of states at the Fermi level, and reduces the lithium-ion diffusion barrier from 1.05 eV to 0.75 eV, which is consistent with the enhanced electrochemical performance observed in experiments.

Claims

1. A Mn-doped spinel ZnCo2O4 anode material, characterized in that: The material retains a pure-phase spinel crystal structure, exhibiting uniform and regular 2–5 μm polyhedral micron particles with layered folds and stepped porous structures on the surface. Mn and Co exist in mixed valence states of Mn²⁺ / Mn³⁺ and Co²⁺ / Co³⁺. First-principles calculations using DFT confirm that Mn doping transforms the material from a semiconductor to a metallic conductor, resulting in the disappearance of the band gap, a significant increase in the Fermi level electronic state density, and a reduction in the lithium-ion diffusion barrier from 1.05 eV to 0.75 eV.

2. The material as described in claim 1, wherein the preparation method comprises: a. Dissolve manganese acetate, zinc acetate, cobalt acetate and urea in distilled water according to the stoichiometric ratio, and stir until completely dissolved to obtain a precursor solution; b. Clean the nickel foam with hydrochloric acid, deionized water, and anhydrous ethanol using ultrasonic cleaning, and then dry it for later use. c. Place the precursor solution and nickel foam in a high-pressure reactor and hydrothermally react at 160°C for 10 hours. After cooling, wash and dry to obtain the precursor. d. The precursor was heated to 350℃ at a rate of 2℃ / min, calcined in air for 5 hours, and then naturally cooled to obtain Mn-doped Mn. 0.5 Zn 0.5 CO2O4 material.

3. The application of the material as described in claim 1 in the negative electrode of a lithium-ion battery.

4. The material as described in claim 1, characterized in that: The reversible specific capacity is significantly improved at a current density of 0.1 A·g⁻¹, the capacity retention is excellent after 200 cycles, the coulombic efficiency is stable, and the overall electrochemical performance is better than that of pure phase ZnCo₂O₄.

5. The material as described in claim 1, characterized in that: It exhibits excellent rate performance within the 0.1~1.0A・g⁻¹ current range, with rapid capacity recovery after high-current discharge; significantly reduced charge transfer resistance, greatly improved lithium-ion diffusion coefficient, and synergistic enhancement of ion transport and charge transfer kinetics.

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