N-doped δ-MnO2 synthesized by the hydrothermal method and its electrochemical performance as anode materials

(N)-doped delta-MnO2 anode materials have been synthesized using a hydrothermal method with urea as the nitrogen source. Structural characterization showed that MnO2 does not change its crystal structure after being doped with the appropriate N3- ions. X-ray photoelectron spectrometer (XPS) results demonstrated that (N3-) ions enter the interstitial positions of the lattice as well as replacing oxygen ions in MnO2, with the formation of oxygen vacancies. Morphological analysis showed that the MnO2 particles doped with moderate numbers of N3- ions present a hierarchical porous nanostructure. Electrochemical impedance spectral analysis showed that, following N-doping, the charge transfer resistance of MnO2 decreases and its lithium-ion diffusion coefficient increases. The rate performance and cycling stability of MnO2 were clearly improved following N-doping. At a molar ratio of urea to manganese of 10% in the precursor solution, the synthesized product (M10 N) showed the best electrochemical performance, which gave reversible capacities of 326.5 mAh g(-1) after cycling at 1 A g(-1) for 300 times and 576.1 mAh g(-1) after cycling at 0.2 A g(-1) for 100 times. The stable structure and high electrical conductivity endowed M10 N with electrochemical properties that performed remarkably well.

Automated summary

(N)-doped delta-MnO2 anode materials were synthesized using urea as the nitrogen source. XPS results showed that (N3-) ions entered the lattice interstitial positions and replaced oxygen ions in MnO2. Morphological analysis revealed a hierarchical porous nanostructure in MnO2 particles doped with moderate numbers of N3- ions. The electrochemical properties of MnO2 were significantly improved following N-doping, with the best performance achieved at a molar ratio of urea to manganese of 10%.