Synergetic Effect of RuO2 Nanosheets as a Redox Active Binder for Aqueous Electrochemical Capacitors: The Case of MnO2

Abstract

MnO2 has been considered as a promising positive electrode material for aqueous electrochemical capacitors combined with activated carbon negative electrodes. Owing to the low electronic conductivity of MnO2, carbon is usually added in large quantities, in particular, for high power applications. In this study, we have pursued the possibility of using RuO2 nanosheets with high electronic conductivity and specific capacitance as a redox active binder. By adding only 20 mol% RuO2 nanosheets to MnO2, an increase in specific capacitance per total mass of composite electrode was observed. Notably, the enhancement effect was particularly pronounced at high scan rates with an increase in specific capacitance of 6.7 times at 50 mV s−1 by using RuO2 nanosheet binder, while at 2 mV s−1 the enhancement was 1.3 times. The cause of the enhancement in specific capacitance and rate performance is discussed based on RuO2 nanosheets acting as redox active conductive binder and MnO2 particles acting as spacers to suppress re-stacking of RuO2 nanosheets.

Keywords

• pseudocapacitor
• mno2
• ruo2 nanosheets
• redox active binder