Tungsten Oxide for Proton Batteries and Its Storage Mechanism

Abstract

The proton insertion capability of a new composite, tungsten oxide hydrate, WO3•0.6H2O, synthesized in a simple hydrothermal method is demonstrated as an anode material for rechargeable proton batteries using sulfuric acid as the electrolyte. Using Ag/AgCl and active carbon as the reference electrode and counter electrode respectively, the electrochemical performance of WO3•0.6H2O was carried out by using a three electrode cell. The cell shows a reversible proton insertion/extraction reaction with a charge capacity of 90 mAh/g at a rate of 1C, with an average discharge voltage at -0.25 V (vs. Ag/AgCl). The cycling performance tested at 20C, the charge capacity is still stable at 80 mAh/g after 10,000 cycles. XRD rietveld refinement indicates that WO3•0.6H2O is a channel hexagonal structure and the zeolitic waters are located in the center of the interstitial cavities. Ex-situ XRD studies also confirms that the protons are inserted through the bridge oxygen which causes the expansion of the ab plane and shrinkage in the c direction. Pairing it with Prussian blue (Fe/Fe), a 1.5V full proton cell was made and showed a capacity around 50mAh/g (based on the anode) at current rate of 2Ag-1 . These results demonstrate that WO3•0.6H2O is a promising anode material to be utilized for proton batteries.