Charge Storage Mechanism of Li_xWO₃ Hexagonal Tungsten Bronze in Aqueous Electrolytes

Abstract

The electrochemical behavior of the lithium hexagonal tungsten bronze, LixWO3, is investigated herein. The material was synthesized at a low temperature under hydrothermal conditions, yielding nanorod-like particles with growth along the c-axis. Upon cycling in a 5 M LiNO3 aqueous electrolyte, a specific capacity of 71 C.g−1 was obtained at 2 mV.s−1, corresponding to a charge/discharge cycle of 10 min. The charge storage mechanism was elucidated using various complementary techniques, such as electrochemical quartz crystal microbalance (EQCM) and synchrotron operando X-ray absorption spectroscopy (XAS). A desolvation process upon Li+ intercalation into the lattice of the material was evidenced, accompanied by a reversible reduction/oxidation of tungsten cations in the crystal structure upon charge/discharge cycling.

Keywords

• electrochemical capacitors
• tungsten bronze
• <i>operando</i>
• high power electrode
• pseudocapacitance
• electrochemical quartz crystal microbalance