WFU Physics Colloquium

TITLE: High Power Electrochemical Energy Storage with Hydrated and Layered Tungsten Oxides

SPEAKER: Professor Veronica Augustyn,

TIME: Wednesday February 15, 2017 at 4:00 PM

PLACE: Room 101 Olin Physical Laboratory

The most common approach of improving the power capability of energy storage materials has been to decrease the diffusion distance by nanostructuring. Here, we explore a different method to improve the kinetics by investigating the effects of structural water in bulk crystalline, layered tungsten oxides. In theory, such materials can offer improved charge transfer at the interface and fast ion transport in the bulk during electrochemical energy storage. Hydrated tungsten oxides are model materials for the systematic investigation of the effect of structural water for high power energy storage because of their stability in aqueous electrolytes, reversible redox, and multiple hydrated phases. The results show that hydrated tungsten oxide exhibits surface-limited (pseudocapacitive) kinetics even with high mass loadings and large crystallite sizes, which leads to high power capability. On the other hand, the anhydrous tungsten oxide exhibits primarily semi-infinite diffusion-controlled kinetics, typical of battery materials. In situ Raman microscopy of the hydrated tungsten oxide points to the presence of reversible proton-induced semiconductor-to-metal transition during electrochemical energy storage. As a result, the hydrated oxides exhibit both fast proton and electron transport. This research identifies an approach for improving power capability in energy storage materials that does not require nanostructuring via the use of interlayer structural water.