Efficient ion transport in activated carbon capacitors assembled with gelled polymer electrolytes based on poly(ethylene oxide) cured with poly(propylene oxide) diamines

The beneficial feature of the polymeric framework in a gel electrolyte is to assist ion transport via the segmental motion of the polymer chains. This feature was displayed by ac impedance analysis on an activated carbon capacitor assembled with a gel electrolyte, which consisted of poly(ethylene oxide)-co-poly(propylene oxide) as a host, propylene carbonate (PC) as a plasticizer, and LiClO4 as an electrolytic salt. A smaller resistance was found for the cell assembled with the gel electrolyte relative to that for a cell with a LiClO4/PC liquid electrolyte, even if the gel and liquid electrolytes had similar conductivities. It is suggested that the polymer chains enhanced the contact between the electrolyte and carbon surface and promoted ion transport through the concentration-graded solvent channel near the interface. The polymer-assisted transport also led to more efficient ion diffusion inside carbon micropores. Constant phase element analysis of the capacitive behavior in micropores showed that the presence of polymer chains did not affect the surface characteristic for double layer formation. This developed gel electrolyte promoted the power performance of activated carbon electrodes by enhancing the transport of electrolyte ions inside and outside the micropores.