Investigating the Cycling Stability of FeWO Pseudocapacitive Electrode Materials.

The stability upon cycling of FeWO used as a negative electrode material for electrochemical capacitors was investigated. The material was synthesized using low temperature conditions for the first time (220 °C). The electrochemical study of FeWO in a 5 M LiNO aqueous electrolyte led to a specific and volumetric capacitance of 38 F g and 240 F cm when cycled at 2 mV·s, respectively, associated with a minor capacitance loss after 10,000 cycles. In order to investigate this very good cycling stability, both surface and bulk characterization techniques (such as Transmission Electron Microscopy, Mössbauer spectroscopy, and magnetization measurements) were used. Only a slight disordering of the Fe cations was observed in the structure, explaining the good stability of the FeWO upon cycling. This study adds another pseudocapacitive material to the short list of compounds that exhibit such a behavior up to now.