Supercapacitor characteristics of pressurized RuO2/carbon powder as binder-free electrodes
RuO2/carbon powder electrodes have been designed to be enclosed in a supercapacitor cell and compressed under a constant pressure (4.84 kgf cm−2), which could overcome binder failure under repeated volumetric changes. In this binder-free powder electrode system, the resistance and ESR are substantially decreased (0.39 Ω at 1 kHz) and the capacitive retention is also greatly improved (7% decrement after 4000 cycles) with a maximum specific capacitance of 835 F (g of total electrode weight)−1, corresponding to 1391.7 F (g of RuO2 weight)−1, which is likely close to the intrinsic energy-storage capability of RuO2 materials. Comparing the specific capacitances at different discharge rates of 5 mV s−1 and 100 mV s−1, a decrement of only 24% occurs in specific capacitance, which is considered to be excellent in RuO2 systems. Furthermore, in the Ragone plot analysis, the developed binder-free system shows an excellent energy and power density of 24.9 W h kg−1 and 16.1 kW kg−1, respectively, at 50 mV s−1, which are ca. 63.2% and 44.7% higher, respectively, than those of a typical binder-containing system (11.1 W h kg−1 and 7.2 kW kg−1).