Chaojun Cui

A new method to prepare vanadium oxide nano-urchins as a cathode for lithium ion batteries

Urchin-like vanadium oxide nanotube clusters, abbreviated to VOx-NUs, were synthesized using a new method. Vanadium pentoxide, having a layered structure, was modified by lithium fluoride (LiF) and transformed into bi-phase lithium vanadate as the inorganic precursor. Then, VOx-NUs were prepared by hydrothermal reaction with dodecylamine as a template. This is different from other molecular assembly methods reported. VOx-NUs-350 nano clusters were obtained by annealing VOx-NUs at a temperature of 350 °C in air. Both samples were identified as three dimensional urchin-like nano clusters. Based on the characterization data obtained, a formation mechanism was established. By simply varying the LiF stoichiometric ratio, the nano tube density of the VOx-NUs could be controlled. VOx-NUs presented a higher initial rate capacity of 400 mA h g−1 and VOx-NUs-350 maintained a better capacity of 150 mA h g−1 after 50 cycles at a 100 mA g−1 current density between 1.5 and 4 V versus Li/Li+.

Carbon nanospheres as an anode material for lithium ion batteries with excellent rate capability

Carbon nanospheres (CNSs) are prepared with natural gas as a carbon source. The resulting sample as an anode material for LIBs delivers a reversible capacity of 552 mA h g−1 at a current density of 0.05 A g−1 with an initial coulombic efficiency of 68%. Moreover, the rate capability is evaluated at different current densities from 0.05 to 5 A g−1, and the coulombic efficiency can still be maintained above 90% after 300 cycles.

Effects of Mn dopant on tuning carrier concentration in Mn doped ZnO nanoparticles synthesized by co-precipitation technique

Zn1 − xMnxO (x = 0.002–0.01) nanoparticles were synthesized by co-precipitation method. The detailed crystal structure and compositional characterizations were characterized by the XRD patterns, Raman spectra, XPS, HRTEM and SEM. the XRD and XPS results show the Mn2+ ions are substitute for Zn2+ ions in the ZnO matrix. In the Raman spectra, the E2(high) peak shifts to lower frequency and the higher intensity of A1(LO) peak appears in the sample with increasing doping concentrations of Mn, indicating a higher concentration of donor defects are introduced in ZnO nanoparticles. Then, the carrier concentration induced by oxygen vacancies are analyzed from the optical absorption spectra. By analyzing the O1s XPS spectrum by Lorentz fitting and PL spectra by Gaussian fitting, the oxygen vacancy concentration increases with Mn doping concentration. The present results suggest that the doped Mn2+ ions play a significant role on enhancing the carrier concentration of ZnO materials.