467844 Freestanding V2O5-PEDOT Thin Film Electrode for Rechargeable Aqueous K-Ion Energy Storage
Rechargeable aqueous electrochemical energy storage (EES) devices are a promising technology for a wide range of energy storage applications due to their low cost and superior safety compared to Li-ion batteries. However, their low energy density has inhibited implementation. Materials with layered structures possess favorable characteristics for improving the energy density of aqueous EES devices. In particular, for aqueous EES using cations with larger ionic radii (e.g. Na-ions and K-ions), which are more abundant and therefore, more sustainable as well as less expensive than Li-ions. Herein we report the exfoliation of bulk vanadium pentoxide using the conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) via a wet chemical method. The resulting exfoliated V2O5-PEDOT:PSS metal oxide-polymer composite can be fabricated into freestanding thin film electrode with simple processing techniques. Structural characterization of the exfoliated V2O5-PEDOT:PSS composite was investigated with various techniques including synchrotron X-ray diffraction and neutron total scattering analyzed in real space with the Atomic Pair Distribution Function. A structural rearrangement from bulk vanadium pentoxide to a structure with large interlayer spacing and a coherence length on the nanoscale is observed upon exfoliation. Cyclic voltammetry measurements conducted in a 1M KCl electrolyte and 1V potential window show multiple redox features, which remain visible at all scan rates tested between 10 and 1000 mV/s. The exfoliated V2O5-PEDOT:PSS nanocomposite not only has the ability for high capacity K-ion storage (605 F/g at 10 mV/s, or 168 mAh/g 100s discharge time) but also the ability to operate at fast charge-discharge rates (203 F/g at 1 V/s, or 56 mAh/g at a 1s discharge time). This work demonstrates a scalable top down approach for the development of a freestanding, high capacity and high power nanocomposite electrode for aqueous K-ion energy storage.