Y.G. Zheng

Advanced Nanostructured Anode Materials for Sodium-Ion Batteries

Sodium-ion batteries (NIBs), due to the advantages of low cost and relatively high safety, have attracted widespread attention all over the world, making them a promising candidate for large-scale energy storage systems. However, the inherent lower energy density to lithium-ion batteries is the issue that should be further investigated and optimized. Toward the grid-level energy storage applications, designing and discovering appropriate anode materials for NIBs are of great concern. Although many efforts on the improvements and innovations are achieved, several challenges still limit the current requirements of the large-scale application, including low energy/power densities, moderate cycle performance, and the low initial Coulombic efficiency. Advanced nanostructured strategies for anode materials can significantly improve ion or electron transport kinetic performance enhancing the electrochemical properties of battery systems. Herein, this Review intends to provide a comprehensive summary on the progress of nanostructured anode materials for NIBs, where representative examples and corresponding storage mechanisms are discussed. Meanwhile, the potential directions to obtain high-performance anode materials of NIBs are also proposed, which provide references for the further development of advanced anode materials for NIBs.

Evaluation of the dissolved oxygen-related electrochemical behavior of pure titanium in acidic fluoride-containing solutions

AbstractThe effects of dissolved oxygen (DO) on the corrosion behavior of pure titanium in acidic fluoride-containing acids (pHu2009=u20090.6–2.0) were evaluated by electrochemical methods, such as open circuit potential (OCP) measurements, potentiodynamic polarization tests, and electrochemical impedance spectroscopy (EIS), combined with surface characterization by X-ray photoelectron spectroscopy (XPS). The results showed that DO affected the anodic kinetic parameters, except the passive current density, by decreasing the maximum anodic current density as well as influencing its dependence on pH and the fluoride concentration. However, DO had no detectable contribution to the total cathodic process at potentials in the active region of titanium. The critical fluoride concentration for the corrosion of titanium was consistently determined by means of three kinds of electrochemical methods. The critical value increased with the DO content, and its dependence on pH was also affected by DO, which were attributed to the effects of DO on the anodic parameters. Additionally, multiple corrosion potentials were discovered under some specific conditions with DO, which resulted from the non-negligible contribution of ORR to the total cathodic current density at relatively higher potentials.n Graphical Abstractᅟ

Effects of dissolved oxygen on the electrochemical corrosion behavior of pure titanium in fluoride-containing weakly acidic solutions

AbstractThe effects of dissolved oxygen (DO) on the electrochemical behavior of titanium in fluoride-containing weakly acidic solutions (pHu2009=u20095.0) were evaluated quantitatively by electrochemical methods, such as open circuit potential (OCP) measurements and potentiodynamic polarization tests, combined with corrosion morphology observation. The results showed that the electrochemical behavior changed from spontaneously passive to active-passive behavior with increasing the fluoride concentration irrespective of the DO content. DO was found to increase the critical fluoride concentration for the corrosion of titanium due to the increased limiting diffusion current density of oxygen reduction reaction and decreased maximum anodic current density caused by DO. But the corrosion rate of titanium would be accelerated by DO once the fluoride concentration exceeded the critical value. Moreover, corrosion products were observed on the surface when the fluoride concentrations were high enough and titanium was in the active state, which altered the electrochemical behavior of titanium further, such as facilitating the occurrence of OCP oscillation.n Graphical abstractᅟ