Supercapacitors Using Binder-Free & Surfactant-Free CNT Electrodes

Abstract

The rapidly increasing technological advances in society place more demands on efficient energy storage and the correspondingly important fast release of the stored energy. Supercapacitors are utilized where energy needs to be stored and released quickly, however they exhibit limitations to these demands that arise from various sources within the device such as the necessary incorporation of resistive additives to the electrode formulation. In the case of activated carbon (AC) electrodes, this constitutes the insulating binder, while for carbon nanotube (CNT) electrodes, the inclusion of appropriate surfactant is almost always necessary to promote stable dispersion for processing. This work discusses the use of surfactant-free and binder-free CNT electrodes for the fabrication of supercapacitor devices. The performance characteristics from pouch cells containing such CNT electrodes in organic electrolytes were benchmarked against commercial-grade AC supercapacitor devices on both cell volume and cell weight bases. EDLC performance advantages realized from eliminating the additives of surfactant and binder were significantly lower ac impedance at low temperature operation (80% reduction @ -30°C), higher capacitance retention after 100,000 cycles, and superior retention of capacitance at high temperature (95% of initial capacitance @ 70°C). The CNT-based supercapacitors of this work exhibited these performance advantages while still maintaining very competitive energy and power densities.