Performance and low temperature behaviour of hydrous ruthenium oxide supercapacitors with improved power densities

The performances of hydrous Ru oxide supercapacitors have been characterized by cyclic voltammetry, constant current discharge, and impedance experiments. The effective series resistance (ESR) was reduced to 0.10 Omega cm 2 by using a Nafion (R) NRE 211 separator, providing a power density of over 100 kW kg(-1) at 5 W h kg(-1), calculated for discharge from 1.0 to 0.5 V. The maximum energy density was 21.8 W h kg(-1) (31.2 W h kg(-1) for discharge to 0 V). Both the ESR and electrode ionic resistance increased exponentially with decreasing temperature, while the specific capacitance decreased linearly from 770 F g(-1) at 40 degrees C to 690 F g(-1) at -40 degrees C. At -40 degrees C the energy loss at 500 W kg(-1) was 15% relative to +25 degrees C.