Size Effect of RuO2-Based 2D Conductive Binder

Abstract

In an electrode mixture MnO2 is one of the most well studied pseudocapacitive material for aqueous supercapacitors owing to the surface and near surface-confined redox processes. A large amount of conducting additive, generally 20-30 wt% acetylene black, needs to be added to achieve high-rate charge storage. Since the conducting additive does not contribute much to the specific capacitance, this leads to decrease in total energy density of the cell in terms of both mass and volume. Polymeric binders such as PTFE and PVdF are also necessary to fabricate rigid electrode with good contact. As an alternative to these typical conductive binders and polymer binders, we have studied the possibility of using RuO2 nanosheets as a novel inorganic binder with polymeric properties, high electronic conductivity and excellent pseudocapacitive properties. For example, by adding only 10-20 mol% of RuO2 nanosheets to particulate MnO2, a large synergetic effect is observed leading to a high utilization of MnO2 pseudocapacitance.[1] The optimized amount of RuO2 in the composite was 13 wt%, which is much lower than the amount generally used for conductive carbon additives despite the 10 times higher formula weight of RuO2 compared to carbon. In this work, we report the electrochemical properties of nanosheet composite electrodes composed of highly conductive RuO2 nanosheets (RuO2(ns)) and poorly conductive MnO2 nanosheets (MnO2(ns)) with various composition and nanosheet size.