Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping.

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO6 octahedra by the addition of edge-sharing NbO6 octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb2O5·15WO3 nanowires with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb2O5·15WO3 nanowires do exhibit more advantages over h-WO3 nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity(71 mAh/g, at 10C, 1C = 100 mA/g), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H+ diffusion kinetics. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of hydrogen ion batteries.